To evaluate temporal and spatial variability along the Valley, samples from different regions have been taken for microbial analyses during the wet and dry seasons.Zone 1 (south) uses raw wastewater for irrigation and has shown higher concentrations of biological indicators than Zones 2 or 3 which correspond to areas with some sedimentation and dilution (rainfall and groundwater). This variability was due to the nature of the wastewater but there was a large decrease in the *Giardia* spp. content in all zones during the dry season. Helminth eggs showed little variability within the three zones and there was no obvious difference between the wet and dry seasons. However, both *Giardia* spp. and helminth eggs were relatively high in zone 3 at the farther reaches of the distribution system, which suggests a possible direct contribution from local discharges, since population in this zone is relatively high (Figure 4). The concentra‐ tions of microorganisms reported are similar to those previously described for untreated wastewater in Mexico [19] and are similar to untreated wastewater from other countries [21, 22], but much greater than concentrations seen in effluents of treatment plants [19].

**Table 1.** Microbiological quality of raw wastewater and characteristics of selected indicators (values in parenthesis indicate range of concentration).

Although it was expected that concentrations of microorganisms would be lower in the wet season due to rainfall dilution, this happens intermittently as the wet season is characterized by irregular intense storms. An additional issue is that the wastewater is mixed with stored rainwater and wastewater depending on the amount of water required by farmers and thus its quality exhibits some variability.

**Figure 4.** Concentration of selected microorganisms in different zones of the Tula Valley (Adapted from [10] and [23])

#### *4.3.2. Emerging pollutants*

and dry seasons. However, both *Giardia* spp. and helminth eggs were relatively high in zone 3 at the farther reaches of the distribution system, which suggests a possible direct contribution from local discharges, since population in this zone is relatively high (Figure 4). The concentra‐ tions of microorganisms reported are similar to those previously described for untreated wastewater in Mexico [19] and are similar to untreated wastewater from other countries [21,

environmental conditions.

6.53 ± 0.58 (5.15-7.84) Traditional indicator of faecal contamination; may indicate the presence of pathogens; behaves similarly to other bacteria under different

5.15 ± 1.0 (2.04-6.20) Intestinal bacteria found in the faeces of all warm-blooded mammals; useful

4.70 ± 0.81 (3.00-5.97) Anaerobic bacteria that have been recently used as an indicator of faecal

3.63 ± 0.77 (2.41-6.41) Viruses that infect bacteria; used as indicators based on ease of detection by

organism represents a serious health risk.

for indicating the quality of water for recreational use and also for reuse.

analytical laboratories; the coliphage group has been the best model for enteroviruses, given their similar physical structure and their greater resistance to treatment processes (such as chlorination); it is always present and relatively abundant in wastewater; easily detected over a short time

Pathogenic protozoa; single celled organisms that develop in two ways: as trophozoites, and as cysts; Infection results from the consumption of a mature cyst that is resistant to the gastric juices; the trophozoites can become cysts again in a process that is apparently aided by unideal luminal conditions, and they are then expelled in the faeces of persons with symptoms of the illness or with no apparent symptoms. Cysts can survive and remain active for weeks, months or even for periods of up to 7 years; capable of forming cysts (resistant structures) under adverse conditions, this

Group of parasitic and free-living worms of various sizes and shapes; they cause mechanical deterioration, tissue damage, toxic effects, and blood loss; intestinal parasites cause anaemic malnutrition and/or delayed growth; they present high resistance to chemical and physical conditions and thus are considered the most resistant form of parasites; they have the ability to survive long periods of time in biosolids and soil (up to 6 years after their

contamination; they form a resistant spore commonly found in faeces which is more resistant to disinfection and adverse environmental conditions that many pathogens; the presence of vegetative cells indicates recent contamination while spores imply prior contamination.

22], but much greater than concentrations seen in effluents of treatment plants [19].

period (24 h).

initial application).

**Table 1.** Microbiological quality of raw wastewater and characteristics of selected indicators (values in parenthesis

**Parameter Concentration Description**

Faecal Coliforms, Log(CFU/100 mL)

*Streptococcus faecalis*, Log(CFU/100 mL)

*Clostridium perfringens* spores, Log(CFU/100 mL)

Somatic bacteriophages, Log (PFU/mL)

*Giardia* spp., Cysts/L 2,231 ± 231

Helminth eggs, eggs/L 13.1±6.2

indicate range of concentration).

(450-10,000)

40 Irrigation and Drainage - Sustainable Strategies and Systems

(1.8-23.0)

Emerging pollutants are defined as those unregulated pollutants that may be controlled by future regulations depending on their potential effects on health and ecosystems [24]. Advan‐ ces in analytical techniques for their detection and an increased understanding of their effects on public health and the environment, has increased the need to establish discharge limits worldwide. During the last two decades, the study of emerging pollutants (such as pharma‐ ceuticals, personal care products, and endocrine disruptors included as additives of gasoline, plastics, or detergents) in the environment has gained scientific attention. Many of these studies have been performed in aquatic ecosystems in the United States of America and Europe [24]. However, for most of the emerging pollutants there are still insufficient data to indicate their risk and ecotoxicity and thus their effects on human health or aquatic organisms remains unknown. Many of these compounds reach the environment through wastewater and they may be removed in wastewater facilities, however, some of them remain in treated effluents and enter the environment, eventually reaching groundwater [25, 26].

Initial reports on pharmaceuticals in wastewater were published in the United States in the 1970's [27], however, even though their presence has been related to fish toxicity, little attention has been given to them [28, 29]. Considering that developed countries have detected emerging pollutants in water and wastewater, even after treatment, their presence in wastewater from the Metropolitan Area of the Valley of Mexico was clearly expected. Furthermore, the fact that many prescription drugs in developed countries are considered over-the-counter medications in Mexico, there is a higher probability of finding their active ingredients in wastewater.

On the other hand, agricultural irrigation favors the transport of pollutants, such as pesticides, from soil to groundwater. Several factors influence their incidence in groundwater, including soil permeability, the depth of the unsaturated zone, geological composition, as well as the solubility, partition (Ko/w), and dissociation (pKa) values of the pollutant. These conditions may promote their adsorption to soil particles or their leaching to groundwater. It has been reported that wastewater irrigation, treated or untreated, increases the concentration of pesticides in groundwater [30].

As mentioned previously, the presence of emerging pollutants was expected in wastewater from the MAVM, and thus at the Tula Valley, and was confirmed by different studies. Some of them [31] analyzed wastewater samples and found a variety of compounds with the exception of clofibric acid. Concentrations found were similar to those reported for wastewater samples taken at treatment plants (Table 2), but higher than those reported for their effluents [32, 33]. The concentrations of naproxen, a widely use pharmaceutical in Mexico, as well as salicylic acid were higher than those reported in other countries, while ibuprofen, diclofenac, are variable in comparison. Other compounds like 4-nonylphenol and diethylhexyl phthalate were the predominant endocrine disruptors in wastewater. Levels of Triclosan, bisphenol-A, butylbencylphtalate, estrone, and 17β-estradiol were similar to those reported elsewhere [33].

It was observed that dilution occurred during the rainy season when reported concentrations of endocrine disruptors were about half of those during the dry season. It should be noted that wastewater at the Tula Valley includes precipitation from the MAVM. Nonetheless, acid pharmaceuticals remain similar in both seasons which may suggest another phenomenon.

Siemens *et al*. [39] concluded that six acid and five basic pharmaceuticals measured in raw wastewater, irrigation water, and spring water, were reduced in concentration along the wastewater distribution canals. However, the authors suggest that acid compounds may permeate clay soils and exhibit poor removal compared to basic or neutral chemicals. Never‐ theless, none of the reported compounds were found in spring water.

a [34, 35] b [36]; c [25]; d[37]; e [38]; f [31].

ceuticals, personal care products, and endocrine disruptors included as additives of gasoline, plastics, or detergents) in the environment has gained scientific attention. Many of these studies have been performed in aquatic ecosystems in the United States of America and Europe [24]. However, for most of the emerging pollutants there are still insufficient data to indicate their risk and ecotoxicity and thus their effects on human health or aquatic organisms remains unknown. Many of these compounds reach the environment through wastewater and they may be removed in wastewater facilities, however, some of them remain in treated effluents

Initial reports on pharmaceuticals in wastewater were published in the United States in the 1970's [27], however, even though their presence has been related to fish toxicity, little attention has been given to them [28, 29]. Considering that developed countries have detected emerging pollutants in water and wastewater, even after treatment, their presence in wastewater from the Metropolitan Area of the Valley of Mexico was clearly expected. Furthermore, the fact that many prescription drugs in developed countries are considered over-the-counter medications in Mexico, there is a higher probability of finding their active ingredients in wastewater.

On the other hand, agricultural irrigation favors the transport of pollutants, such as pesticides, from soil to groundwater. Several factors influence their incidence in groundwater, including soil permeability, the depth of the unsaturated zone, geological composition, as well as the solubility, partition (Ko/w), and dissociation (pKa) values of the pollutant. These conditions may promote their adsorption to soil particles or their leaching to groundwater. It has been reported that wastewater irrigation, treated or untreated, increases the concentration of pesticides in

As mentioned previously, the presence of emerging pollutants was expected in wastewater from the MAVM, and thus at the Tula Valley, and was confirmed by different studies. Some of them [31] analyzed wastewater samples and found a variety of compounds with the exception of clofibric acid. Concentrations found were similar to those reported for wastewater samples taken at treatment plants (Table 2), but higher than those reported for their effluents [32, 33]. The concentrations of naproxen, a widely use pharmaceutical in Mexico, as well as salicylic acid were higher than those reported in other countries, while ibuprofen, diclofenac, are variable in comparison. Other compounds like 4-nonylphenol and diethylhexyl phthalate were the predominant endocrine disruptors in wastewater. Levels of Triclosan, bisphenol-A, butylbencylphtalate, estrone, and 17β-estradiol were similar to those reported elsewhere [33].

It was observed that dilution occurred during the rainy season when reported concentrations of endocrine disruptors were about half of those during the dry season. It should be noted that wastewater at the Tula Valley includes precipitation from the MAVM. Nonetheless, acid pharmaceuticals remain similar in both seasons which may suggest another phenomenon.

Siemens *et al*. [39] concluded that six acid and five basic pharmaceuticals measured in raw wastewater, irrigation water, and spring water, were reduced in concentration along the wastewater distribution canals. However, the authors suggest that acid compounds may permeate clay soils and exhibit poor removal compared to basic or neutral chemicals. Never‐

theless, none of the reported compounds were found in spring water.

and enter the environment, eventually reaching groundwater [25, 26].

42 Irrigation and Drainage - Sustainable Strategies and Systems

groundwater [30].

**Table 2.** Concentration of pharmaceutical compounds in wastewater.

#### **4.4. Natural attenuation of basic parameters, organic pollutants and pathogens in soil**

In the Tula Valley, known as the largest case of indirect wastewater reuse for human con‐ sumption in the world, natural soil aquifer treatment (SAT) has been taken place for more than 100 years, recharging the aquifer and acting as a barrier to prevent contaminants from entering it. The local aquifer is being recharged at a rate of 25 m3 /s due to the infiltration of untreated wastewater from unlined irrigation channels, storage dams, and excess water used for irrigation (flood irrigation practice; [12]). During percolation, natural soil infiltration occurs through unsaturated soil; as the effluent moves through the soil and the aquifer, it can undergo significant quality improvements through physical, chemical and biological processes.

Non-intentional natural SAT has treatment benefits in the unsaturated zone in the Tula Valley. It acts as a natural filter, and produces groundwater of acceptable quality due to the charac‐ teristics of the soil-aquifer structure, the residence time, and the history of the complex geohydrological system. Table 3 showed the historical data of wastewater and aquifer water quality variability obtained from studies performed at the site. It indicates that parameters related with salinity behavior are present in groundwater, in addition to parameters such as nitrate, and solids in dissolved phase. In contrast, the percentage removal of pathogenic organisms and emerging pollutants through unsaturated soil is greater than 50%.

There is evidence that during infiltration the vast majority of microorganisms are retained in the first few centimeters of soil [40], however their potential fate is influenced by size ranges of microorganisms (20-80 μm for helminth eggs, 1 μm for bacteria, 4-12 μm for protozoa), type of soil, and even soil organic matter content for bacteriophages (20 to 200 nm), and therefore for viruses; thus the migration of microorganisms through soil does not always allow complete attenuation.

Adapted from [23, 31, and 39] (ND: Not detected LOD: Lower limit of detection).

**Parameters Units**

44 Irrigation and Drainage - Sustainable Strategies and Systems

**Wastewater (Min-Max)**

**Basic analysis** Total Dissolved Solids, TDS mg/L 409-1123 546 -1586 -55.5 Alkalinity mg/L 324-600 256-748 -7.8 Nitrate (as N) mg/L 0.02-0.47 0.0-32 -8014 **Salinity related analysis** Electrical conductivity μS/cm 1734-3000 1755 -4187 -18.0 Redox potential mV -51 - -37 -79.1 - -11.0 -38.7 Sodium mg/L 56-215 103 -361 -38.3 Potassium mg/L 19-13190 10.5 -107 98.0 Hardness Ca mgCaCO3/L 90-131 70-787 -218.4 Hardness Mg mgCaCO3/L 12-51 17 -301 -65.7 Total hardness 122-172 114-1006 -181.8 Bicarbonate mg/L 270-504 212-652 -12.8 Sulfate mg/L 53-2492 190 -3025 -15.0 **Microbiological analysis** Total Bacteria count (37 ºC) Log CFU/100 mL 6.4-7.7 1.3-4.2 57.6 Faecal coliforms Log CFU/100 mL 5.6-7.5 0.0-2.9 70.8 Enterococci Log CFU/100 mL 2.3-5.9 0.0-1.9 79.3 Clostridium spores Log CFU/100 mL 3.2-5.6 0.0-2.6 61.1 Somatic Bacteriophages Log PFU/100 mL 2.5-4.9 0.0-2.8 52.6 *Giardia* spp*.*  Water quality variability for wastewater and the Tula Valley aquifer and natural removal percentages (SAT)

Data recorded over many years regarding the attenuation of emerging pollutants through soil show a mean reduction of 86 percent of the chemical load in the wastewater used for irrigation (Table 3). The main attenuation processes such as adsorption and biodegradation have been confirmed in experimental studies with local soil samples, and enriched samples [23]. The most important result of this research is the observation that large amounts of suspended and dissolved organic matter in soils [41], and even in raw wastewater, improve the adsorption of emerging pollutants in soils, and therefore their final low content in groundwater; this verifies previously published results with regard to the role of natural SAT in removing pollutants [26, 42]. In fact, the sorption behavior of three pharmaceuticals (naproxen, carbamazepine, and triclosan), a plasticizer Bis-2 ethyl(hexyl)phthalate, and the surfactant metabolite 4-nonylphe‐ nol in wastewater irrigated soil, was analyzed for different soil depths sampled from the Tula Valley, showing that the potential migration of these compounds to the aquifer depends on the physical and chemical characteristics of soil, such as organic matter content, and clay/sand percentages [43, 44].

Other studies have shown that heavy metals have accumulated in soil in the Tula Valley (for example cadmium, nickel, and lead) and their retention is associated with the length of time that wastewater has been used for irrigation [45].

It should be mentioned that a large wastewater treatment plant is currently under construction to treat the MAVM's wastewater and reduce pollutant load to the Tula Valley. This plant, Atotonilco, is designed to treat 35 m3 /s with a combined process (23 m3 /s with a biological process and 12 m3 /s with a physicochemical process) that may partially remove organic matter and the bulk of pathogens. However, the effect on soil attenuation must be evaluated as Gibson *et al*. [41] suggest that a reduction in the amount of organic matter that gets into irrigated soils may affect sorption processes, which could have an impact on the removal of emerging pollutants, pathogens, and heavy metals.

#### **4.5. Impacts of wastewater irrigation in the Mezquital Valley**

Reuse in the Tula Valley has functioned as a discharge route for the closed basin of the MAVM at a relatively low cost. The characteristics of the water, in terms of organic matter and nutrients have significantly increased crop productivity in the Valley and have allowed farmers to harvest up to five crops per year of alfalfa, fodder oats, tomato, barley, and maize. Resulting yields in the Tula Valley are 71 to 150% higher than those obtained with rain-fed agriculture [19]. Thus, the contribution of nutrients represents estimated annual savings of \$180 to \$200 million USD. To exemplify this, agricultural production for 2011-2012 in the Irrigation Districts of the Tula Valley reached \$418 million USD [46].

Since 81% of the main distribution canals as well as 52% of lateral distribution canals are unlined, 80.2 Mm3 /y of conveyed wastewater infiltrates to the aquifer [47]. It is with this infiltration that wastewater quality is improved before reaching the groundwater through processes like adsorption or biodegradation, which depend on contact time and filtering distance. As an example, travel times from the irrigated fields to the springs are estimated to be 3 to 5 days with groundwater velocities of 0.02 to 6.0 m/d [16].

This infiltration has also incidentally recharged the Tula Valley aquifer for more than 100 years, at a recharge rate estimated at 25 m3 /s and equivalent to 13 times the natural recharge [16]. As a consequence, the water table has risen from a depth of 60 meters in the 1950's to 4 meters in the southern part of the Valley and several springs with flows between 40 and 600 L/s have appeared [16]. The amount of available water with a relatively good quality allows some areas to be used to grow vegetables like tomato, lettuce, cabbage, beetroot, cilantro, radish, carrot, spinach, and parsley [16]. At the same time, surface and groundwater produced by wastewater infiltration provide drinking water to approximately 500,000 people after only treatment with chlorine for disinfection [12].

In contrast, wastewater reuse in the Tula Valley has some negative impacts on the local population and the environment. Due to the pathogens and parasites contained in wastewater, the incidence of gastrointestinal diseases has increased by more than 16 times in children living in the irrigation area, compared to children unexposed to wastewater [48]. In addition, microbial and organic pollutants have been detected in the soil matrix of the irrigation areas at various depths [41, 44]. Heavy metals have accumulated in the upper soil layer [49], and Siebe [45] suggests that eventually the retention capacity of the soil might be exceeded with the risk of groundwater pollution. Moreover, the gradual salinization of local soils has caused the loss of more than 2,000 ha of cropland [17].

#### **4.6. Conventional wastewater treatment processes, control of micropollutants, and hazardous substances in water**

Even though the soil filters a large amount of pollutants from wastewater with removals above 90% [12], some studies have demonstrated that in some areas the filtered water still contains bacteria (coliforms and enterococci) and viruses [40, 50]. Filtered water presents a high concentration of salts (indicated by sodium, sulfates, carbonates, bicarbonates, chloride, calcium hardness, electrical conductivity, and potassium), and furthermore, total dissolved solids and nitrates exceed the limits set by the Mexican regulatory authorities (1,000 and 10 mg/L, respectively).

At the same time, several studies [23, 31, 40, 41, 43, 44] report the presence of emerging pollutants in springs and wells, which poses a health risk to local population (approximately 500,000 inhabitants) that use the water for human consumption (Figure 5). These pollutants exhibit low removal by conventional treatment processes and thus alternative technologies, such as membrane filtration (nanofiltration or reverse osmosis), have been proposed [51]. Different studies have demonstrated that nanofiltration removes emerging pollutants, including those with low molecular weight, in particular pesticides [52], pharmaceuticals [51], and endocrine disruptors [52].

As a result, to improve the quality of spring water in the Tula Valley, a pilot plant with a nanofiltration membrane was installed in the Cerro Colorado Spring (Figure 5) [53]; The pilot plant (11.4 m3 /d) operated for 800 hours and included a pumping system, a prefilter, a softening unit for reducing potential scaling, and a nanofiltration module (Figure 6). The nanofiltration (NF) membrane was selected after laboratory trials on a pilot cell. The pilot plant had the instrumentation required to measure flow, pH, TDS, as well as pressure along the system. Recovery (permeate) was maintained at more than 66 % of the influent.

**Figure 5.** Cerro Colorado Spring at the Tula Valley.

may affect sorption processes, which could have an impact on the removal of emerging

Reuse in the Tula Valley has functioned as a discharge route for the closed basin of the MAVM at a relatively low cost. The characteristics of the water, in terms of organic matter and nutrients have significantly increased crop productivity in the Valley and have allowed farmers to harvest up to five crops per year of alfalfa, fodder oats, tomato, barley, and maize. Resulting yields in the Tula Valley are 71 to 150% higher than those obtained with rain-fed agriculture [19]. Thus, the contribution of nutrients represents estimated annual savings of \$180 to \$200 million USD. To exemplify this, agricultural production for 2011-2012 in the Irrigation Districts

Since 81% of the main distribution canals as well as 52% of lateral distribution canals are

infiltration that wastewater quality is improved before reaching the groundwater through processes like adsorption or biodegradation, which depend on contact time and filtering distance. As an example, travel times from the irrigated fields to the springs are estimated to

This infiltration has also incidentally recharged the Tula Valley aquifer for more than 100 years,

a consequence, the water table has risen from a depth of 60 meters in the 1950's to 4 meters in the southern part of the Valley and several springs with flows between 40 and 600 L/s have appeared [16]. The amount of available water with a relatively good quality allows some areas to be used to grow vegetables like tomato, lettuce, cabbage, beetroot, cilantro, radish, carrot, spinach, and parsley [16]. At the same time, surface and groundwater produced by wastewater infiltration provide drinking water to approximately 500,000 people after only treatment with

In contrast, wastewater reuse in the Tula Valley has some negative impacts on the local population and the environment. Due to the pathogens and parasites contained in wastewater, the incidence of gastrointestinal diseases has increased by more than 16 times in children living in the irrigation area, compared to children unexposed to wastewater [48]. In addition, microbial and organic pollutants have been detected in the soil matrix of the irrigation areas at various depths [41, 44]. Heavy metals have accumulated in the upper soil layer [49], and Siebe [45] suggests that eventually the retention capacity of the soil might be exceeded with the risk of groundwater pollution. Moreover, the gradual salinization of local soils has caused

**4.6. Conventional wastewater treatment processes, control of micropollutants, and**

Even though the soil filters a large amount of pollutants from wastewater with removals above 90% [12], some studies have demonstrated that in some areas the filtered water still contains

/y of conveyed wastewater infiltrates to the aquifer [47]. It is with this

/s and equivalent to 13 times the natural recharge [16]. As

pollutants, pathogens, and heavy metals.

46 Irrigation and Drainage - Sustainable Strategies and Systems

of the Tula Valley reached \$418 million USD [46].

unlined, 80.2 Mm3

at a recharge rate estimated at 25 m3

chlorine for disinfection [12].

**hazardous substances in water**

the loss of more than 2,000 ha of cropland [17].

**4.5. Impacts of wastewater irrigation in the Mezquital Valley**

be 3 to 5 days with groundwater velocities of 0.02 to 6.0 m/d [16].

Nanofiltration demonstrated its effectiveness for removing organic matter (92% of total organic carbon), salinity (60% of total dissolved solids and 75% of electrical conductivity) and 100% for selected microorganisms (faecal coliforms, faecal streptococci, *Salmonella* spp., *Clostridium perfringens*, *Giardia* spp., and bacteriophages). With respect to emerging pollutants, membrane selectivity varied from 5 to 6% for salicylic acid and nonylphenol up to more than 75% for gemfibrozil, butylbenzyl phthalate, carbamazepine, and diclofenac. Treated water (permeate) met the limits for drinking water and thus it could be considered suitable for human consumption.

**Figure 6.** Flow diagram of the nanofiltration pilot plant at the Cerro Colorado Spring, Tula Valley.

Based on such studies, filtered water from the Tula Valley is being considered as a potential source for supplying drinking water for Mexico City and studies have determined that 6.5 m3 / s may be sourced from local groundwater [54].

#### **5. Forthcoming expectations and recommendations**

Findings confirmed by 15 years of research into the complex Tula Valley hydrological and hydraulic system, are:

**•** Wastewater reuse for irrigation has proven to be an alternative in the water-scarce region of Tula Valley.

**•** Agricultural irrigation in the Tula Valley using raw wastewater from the Metropolitan Area of the Valley of Mexico has been performed for more than 100 years and several studies have demonstrated that complex phenomena occur.

Nanofiltration demonstrated its effectiveness for removing organic matter (92% of total organic carbon), salinity (60% of total dissolved solids and 75% of electrical conductivity) and 100% for selected microorganisms (faecal coliforms, faecal streptococci, *Salmonella* spp., *Clostridium perfringens*, *Giardia* spp., and bacteriophages). With respect to emerging pollutants, membrane selectivity varied from 5 to 6% for salicylic acid and nonylphenol up to more than 75% for gemfibrozil, butylbenzyl phthalate, carbamazepine, and diclofenac. Treated water (permeate) met the limits for drinking water and thus it could be considered suitable for human

**Figure 6.** Flow diagram of the nanofiltration pilot plant at the Cerro Colorado Spring, Tula Valley.

**5. Forthcoming expectations and recommendations**

s may be sourced from local groundwater [54].

hydraulic system, are:

of Tula Valley.

Based on such studies, filtered water from the Tula Valley is being considered as a potential source for supplying drinking water for Mexico City and studies have determined that 6.5 m3

Findings confirmed by 15 years of research into the complex Tula Valley hydrological and

**•** Wastewater reuse for irrigation has proven to be an alternative in the water-scarce region

/

consumption.

48 Irrigation and Drainage - Sustainable Strategies and Systems

There is no doubt about the benefits of wastewater reuse for irrigation, but some potential impacts should be considered:

#### **Author details**

I. Navarro\* , A. Chavez, J.A. Barrios, C. Maya, E. Becerril, S. Lucario and B. Jimenez

\*Address all correspondence to<EMAIL_ADDRESS>
Institute of Engineering, UNAM, Mexico

#### **References**

[10] Jimenez, B. and Asano, T. Water reuse: an international survey of current practices, issues and needs. IWA Publishing. ISBN:<PHONE_NUMBER>, 650 pp. 2008.

**Author details**

, A. Chavez, J.A. Barrios, C. Maya, E. Becerril, S. Lucario and B. Jimenez

[1] FAO. Monitoring agricultural water use at country level. Experiences of a pilot project in Benin and Ethiopia. Land and Water Discussion Paper 9. ISSN 1729-0554.

[2] Hamilton A.J., Mebalds M., Aldaoud R., Heath, M. A survey of physical, agrochemi‐ cal and microbial characteristics of waste-water from the carrot washing process: im‐ plications for re-use and environmental discharge. Journal of Vegetable Science.

[3] Peasey A., Blumenthal U., Mara D., Ruiz-Palacios G.A. Review of Policy and Stand‐ ards for Wastewater Reuse in Agriculture: A Latin American Perspective. London

[4] World Health Organization. Guidelines for the Safe Use of Wastewater, Excreta, and Greywater. Vol. 2, Wastewater Use in agriculture. Geneva, Switzerland. 2006.

[5] Blumenthal, U., Peasey, A. Critical Review of Epidemiological Evidence of the Health Effects of Wastewater and Excreta Use in Agriculture. London School of Hy‐

[6] Page, D., Dillon, P., Toze, S., Bixio, D., Genthe, B., Jiménez Cisneros, B.E., Wintgens, T. Valuing the subsurface pathogen treatment barrier in water recycling via aquifers

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[9] Medaware. Development of Tools and Guidelines for the Promotion of the Sustaina‐ ble Urban Wastewater Treatment and Reuse in the Agricultural Production in the Mediterranean Countries. European Commission Euro-Mediterranean-Partnership. Technical Guidelines on Wastewater Utilization. ME8/AIDCO/2001/0151/59341-P033.

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age paper 47 http://www.fao.org/docrep/T0551E/t0551e00.htm

\*Address all correspondence to<EMAIL_ADDRESS>
School of Hygiene & Tropical Medicine. 2000.

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Institute of Engineering, UNAM, Mexico

50 Irrigation and Drainage - Sustainable Strategies and Systems

I. Navarro\*

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## **Impacts of Abattoir Waste-Water Irrigation on Soil Fertility and Productivity**

Raghupathi Matheyarasu, Balaji Seshadri, Nanthi S. Bolan and Ravi Naidu

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/59312

#### **1. Introduction**

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tember 2014)

Water is the most precious resource that exists naturally on the planet earth; yet, global fresh water is only less than 3% and increasing population density [1] has been increasing the pressure on global fresh water resources [2]. More importantly, impacts on freshwater quality and quantity are enormous in the current era of industrialization, modernization, over exploitation, and poor resource management practices.

Increase in global population and decrease in the availability of clean water is limiting human activities, especially industries. Most industrial processes require enormous quantity of water, which almost equally discharges wastewater [3]. Wastewater emerges from both domestic and industrial sources, untreated discharges of wastewater often contains significant amount of pollutants, nutrients and pathogens [4]. Industrial processes need huge quantity of water to meet the quality of products with customer satisfaction. The major industrial sources of wastewater include canneries, milk dairies, Sugar factories, Breweries and distilleries, Beverage industry, Meat industry, Fertiliser manufacture, Pulp and paper, Tanneries and Yeast manufacture [5]. Among the industries generating high volume of wastewater, meat industries act as a major source with the increase in meat intake by people. Agriculture and allied industry consumed the largest volume of water with more than 50 % of Australia's water consumption in 2009-10 [6].

Unsafe water and sanitation practices account for more deaths worldwide from diseases than any war claims [7]. One quarter of the world's population is without safe drinking water [8]. To overcome the pressure on fresh water sources caused by the industry, sustainable alterna‐ tive methods are needed which will reduce the pressure on global fresh water resources as

© 2015 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

well as to meet the demand of water for households, industries and agriculture [9]. There is a wide range of environmental challenges facing the industrial sector globally, especially in the sustainable management of wastewater. With stringent environmental laws in most of the developed nations, industries needed to adopt the existing cost-intensive treatment methods including phytoremediation, land treatment and constructed wetlands [10, 11].

Therefore, development of a low-cost wastewater management technology is needed to treat the wastewater from various sources. Among the low-cost technologies, landfilling has been the most popular and widely followed technology for its convenience in handling and easy maintenance [12]. However, long-term discharge of effluents builds up the levels of nutrients, organic matter and heavy metals posing different kind of threat in terms of land degradation and pollution of surface and underground water resources. Hence, growing plants on the wastewater treated soils can emerge as a sustainable measure towards water resources management, which can be termed as phytoremediation. This approach is not only energy efficient and aesthetically pleasing method of remediating sites with low to moderate levels of contamination but can also be used in combining with other more conventional methods. It will provide potential solutions to reduce the cost of meat production and it will also help to protect our natural resources for the future generation. Overall fresh water consumption is reduced by adopting water efficient techniques and water reuse where water resources are scarce [13]. This book chapter aims to describe the effects of wastewater irrigation on soil fertility and productivity, assessment, mitigation, and farm nutrient budget based on waste‐ water driven nutrient.

#### **2. Global wastewater scenario**

Around 90 per cent of wastewater produced globally remains untreated, causing widespread water pollution. An approximate estimate of global wastewater production is about 30-70 cubic meters per person per year causing significant impacts on the natural environment [14]. Globally, meat industry wastewater act as a major source of industrial wastewater, for example in Australia, meat industry generates an average of 7225 ML /year. The concerns over con‐ serving water resources have led to new innovations for the sustainable management of Australia's wastewater into usable water resources. In the last 30 years, reuse of wastewater for agriculture has been increased due to the decline in fresh water sources, dry weather, heavy runoff loss, and overexploitation [15]. The sources of wastewater are illustrated in Figure 1.

#### **2.1. Wastewater production**

Global water consumption is doubling every 20 years and by the year 2025 two out of three people in the world will be living under water scarcity, especially in under developed and some developing countries [3]. Over 1.1 billion people across the globe lack access to safe drinking water and 2.4 billion to adequate sanitation. As a result, a child dies every 15 seconds from water related diseases [16, 17]. The health of a person depends on the quality and quantity of water for sustaining good health and vigorous life. Since agriculture, households and

21 Impacts of Abattoir Waste-Water Irrigation on Soil Fertility and Productivity http://dx.doi.org/10.5772/59312 57

Figure 1. Sources of wastewater streams **Figure 1.** Sources of wastewater streams

well as to meet the demand of water for households, industries and agriculture [9]. There is a wide range of environmental challenges facing the industrial sector globally, especially in the sustainable management of wastewater. With stringent environmental laws in most of the developed nations, industries needed to adopt the existing cost-intensive treatment methods

Therefore, development of a low-cost wastewater management technology is needed to treat the wastewater from various sources. Among the low-cost technologies, landfilling has been the most popular and widely followed technology for its convenience in handling and easy maintenance [12]. However, long-term discharge of effluents builds up the levels of nutrients, organic matter and heavy metals posing different kind of threat in terms of land degradation and pollution of surface and underground water resources. Hence, growing plants on the wastewater treated soils can emerge as a sustainable measure towards water resources management, which can be termed as phytoremediation. This approach is not only energy efficient and aesthetically pleasing method of remediating sites with low to moderate levels of contamination but can also be used in combining with other more conventional methods. It will provide potential solutions to reduce the cost of meat production and it will also help to protect our natural resources for the future generation. Overall fresh water consumption is reduced by adopting water efficient techniques and water reuse where water resources are scarce [13]. This book chapter aims to describe the effects of wastewater irrigation on soil fertility and productivity, assessment, mitigation, and farm nutrient budget based on waste‐

Around 90 per cent of wastewater produced globally remains untreated, causing widespread water pollution. An approximate estimate of global wastewater production is about 30-70 cubic meters per person per year causing significant impacts on the natural environment [14]. Globally, meat industry wastewater act as a major source of industrial wastewater, for example in Australia, meat industry generates an average of 7225 ML /year. The concerns over con‐ serving water resources have led to new innovations for the sustainable management of Australia's wastewater into usable water resources. In the last 30 years, reuse of wastewater for agriculture has been increased due to the decline in fresh water sources, dry weather, heavy runoff loss, and overexploitation [15]. The sources of wastewater are illustrated in Figure 1.

Global water consumption is doubling every 20 years and by the year 2025 two out of three people in the world will be living under water scarcity, especially in under developed and some developing countries [3]. Over 1.1 billion people across the globe lack access to safe drinking water and 2.4 billion to adequate sanitation. As a result, a child dies every 15 seconds from water related diseases [16, 17]. The health of a person depends on the quality and quantity of water for sustaining good health and vigorous life. Since agriculture, households and

including phytoremediation, land treatment and constructed wetlands [10, 11].

water driven nutrient.

**2. Global wastewater scenario**

56 Irrigation and Drainage - Sustainable Strategies and Systems

**2.1. Wastewater production**

industries are the three sectors which consume majority of water, they generate large volume of wastewater. For example, in Australia domestic wastewater aloneis being produced at 44165 litters per person per year [18], country's total of 1040.3GL/year [6].

Wastewater which has been used at least once, and has thereby been rendered unsuitable for reuse without treatment is being collected and transported through sewers [19]. Industriali‐ zation positively increased the number of industries around globe, and this proficient growth has significant impacts on the natural environment. Since, Australia is among the driest countries on the globe, having very minimal river runoff (about 1%) [20], it's necessary to reuse all the wastewater discharged to natural environment.

#### **2.2. Characteristics of different types of wastewater**

It is important to characterise wastewater before it is being re-used for many purposes. The nature of wastewater depends on the industry type and material processed. For example, the wastewater discharged from abattoir is different from winery; hence the understanding on chemical characteristics is important. Abattoir wastewater derives organic loads from different sources. Animal manure contributes significant amount of pollutants to the abattoir effluent containing N, P, and organic carbon [21]. In comparison with other wastewater sources, abattoir wastewater stream possess the highest concentration of organic load, with increased COD (8000 mg/L), proteins (70 %) and suspended solids (15-30 mg/L) [22].

Piggery effluent contains 158-1025 mg/L of N; 11-123 mg/L of P; 97-1845 mg/L of K and 103-2870 mg/L of Na with other beneficial micro nutrients [23]. According to the APL-AMIC –projects report, water usage, feed grain supply and managing nutrients in the piggery effluents are the major environmental challenges faced by Australian piggeries [24]. Piggery effluents and byproducts can be used as valuable alternatives for fertiliser's agricultural production. Waste‐ water discharged from wineries is rich in nutrients; it contains 1-128 mg of N /L; 1-33 mg of P /L; 19-1250 mg of K /L and 18-880 mg of Na /L [23]. Organic load or waste load in the winery wastewater increases the nutrient content (sodium and potassium) and BOD of the wastewa‐ ter, which may lead to salinity and sodicity [25]. Dairy farm generates large volume wastewater with rich in nutrients especially N and P. Dairy farm wastewater comprises of urine, faeces, chemicals from cleaning, and solid waste (cow dung). This contributes 15-200 mg of N /L; 11-160 mg of P /L; 11-160 mg of K /L [26]. Typical characteristics and nutritional composition of different agricultural industries wastewater is shown in Table-1.

SS – Suspended solids; TDS – Total dissolved solids; BOD – Biological oxygen demand; COD – Chemical oxygen de‐ mand; TOC – Total organic carbon

**Table 1.** Characteristics and constitutes of wastewater from selected sources

#### **2.3. Wastewater disposal and treatment**

Treatment of wastewater, before reuse is most important to avoid the excess load of contam‐ inants such as solids, organic matter, nutrients and pathogens [27]. For example, untreated abattoir wastewater is unsuitable for reuse or discharge into receiving environment. It will cause serious environmental hazards in the receiving environment such as eutrophication, land degradation, nutrient leaching, ground water contamination, greenhouse gas emission and effects on ecosystem value; hence proper reduction in pollutant levels in the prior stage is essential. The various environmental impacts of abattoir wastewater disposal methods are described in the table 2.

**Table 2.** Wastewater disposal methods and their impacts

wastewater increases the nutrient content (sodium and potassium) and BOD of the wastewa‐ ter, which may lead to salinity and sodicity [25]. Dairy farm generates large volume wastewater with rich in nutrients especially N and P. Dairy farm wastewater comprises of urine, faeces, chemicals from cleaning, and solid waste (cow dung). This contributes 15-200 mg of N /L; 11-160 mg of P /L; 11-160 mg of K /L [26]. Typical characteristics and nutritional composition

**Constituents Domestic Textile Abattoirs Piggery Dairy effluent Olive mill Winery** SS (mg L-1)<PHONE_NUMBER> 447 28-1900 2.8-126 60-2000 TDS (mg L-1) 850 1130 3500 3100-8600 138-8500 500-2200 K (mg L-1) 100-400 97-1845 11-160 17100 19-1250

pH 10.2 7.3 7.5-8 5.6-8 4.2-7 4-10 P (mg L-1) 20 3.4 100-400 109 (11-123) 11-160 1.1 1-33

BOD₅ (mg L-1)<PHONE_NUMBER>-7500 40 320-1750 1.5-100 COD (mg L-1)<PHONE_NUMBER><PHONE_NUMBER>-3360 6.4-162

TOC (mg L-1) 2.5 201-6664

Yusuff. 2004. [61]

Oil & Grease (mg L-1)<PHONE_NUMBER> 68-240 2.26

Mittal. 2004. Damien Batstone., 2012. [31,62]

SS – Suspended solids; TDS – Total dissolved solids; BOD – Biological oxygen demand; COD – Chemical oxygen de‐

Treatment of wastewater, before reuse is most important to avoid the excess load of contam‐ inants such as solids, organic matter, nutrients and pathogens [27]. For example, untreated abattoir wastewater is unsuitable for reuse or discharge into receiving environment. It will cause serious environmental hazards in the receiving environment such as eutrophication, land degradation, nutrient leaching, ground water contamination, greenhouse gas emission and effects on ecosystem value; hence proper reduction in pollutant levels in the prior stage is essential. The various environmental impacts of abattoir wastewater disposal methods are

623 (103-2870)

854 (158-1025)

EPA-SA., 2009. [23]

EPA-SA., 2009. Marimoli et al., 2011. [23,26].

60-807 400 18-880

15-200 0.09-3.2 1-128

Anastasiou, 2011. [63]

EPA-SA., 2009. [23]

of different agricultural industries wastewater is shown in Table-1.

Na (mg L-1) 20-150

58 Irrigation and Drainage - Sustainable Strategies and Systems

N (mg L-1) 50- 70 100-150

Huang *et al*., 2010. [60]

**Table 1.** Characteristics and constitutes of wastewater from selected sources

References

mand; TOC – Total organic carbon

described in the table 2.

**2.3. Wastewater disposal and treatment**

Abattoir wastewater must be treated before it reaches the receiving environments, to maintain minimum pollutant standards [28]. Effective abattoir wastewater treatment methods should remove the pollutants, nutrients, organic load, fat, oil crease, blood and pathogens from the wastewater to ensure the low level of toxicants in the final discharge effluent [29]. Abattoir wastewater treatment involves various methods to treat the meat industry effluents and to retain the bio-wealth of an ecosystem.

There are three major types of treatment technologies (primary, secondary, tertiary) that can be used to treat the abattoir wastewater (Figure 2). A typical abattoir wastewater treatment plant should have three kinds of storage system or pond to reuse the treated wastewater into irrigating agricultural crops, the first one is anaerobic pond, followed by aerobic /facultative ponds then a polishing / irrigation pond [29]. Each wastewater treatment technique is evalu‐ ated in the form of its merits and demerits by economic feasibility, technical availability, and socio–cultural acceptability. This kind of evaluation is very important to assume the waste‐ water recycling method to current and future.

**Figure 2.** Wastewater treatment methods

Figure 2. Wastewater treatment methods

Pre-treatments include screening, catch basins, floatation, equalization, and settlers. A primary treatment includes screening, dissolved air flotation (DAF) and flow equalisation [30]. Pretreatments are processes that remove gross solids; coarse suspended floating matter and primary treatments remove readily settleable solids, most commonly by sedimentation [31]. Pre-treatment methods can be used to minimise the organic load and BOD in the wastewater. Pre-treatment methods such as screening and sedimentation helps to reduce 60% of solids and 25-35 % of BOD load from wastewater [32]. Anaerobic process includes lagoons, anaerobic contact anaerobic filter, anaerobic sequencing batch reactor (ASBR), up-flow anaerobic sludge blanket (UASB). An aerobic system includes aerated lagoons, activated sludge process, oxidation ditches, sequencing batch reactors and trickling filters. The advantage of lagoons in the wastewater treatments is high efficiency in organic material (BOD₅) removal, at the same time very poor in N and P removal [33].

The pollutants that remain after primary treatments can be removed by secondary treatment methods, including fine suspended solids, colloidal and dissolved organic matter by biologi‐ cal / chemical treatment by aerobic or anaerobic process. Anaerobic contact reactors (ACR) are the best treatment system that reduces the BOD levels by 90% and volatile solids removal by 41-67 %. The issue with anaerobic reactors is odour generation, which can be minimised by installing synthetic floating covers on the lagoons, to avoid odour as well as to trap biogas [34]. Temperature is one of the limiting factors of anaerobic lagoon, which determine the efficiency of lagoons and most anaerobic lagoons are more effective when temperature is above 21ºC [35]. In many countries aerobic-anaerobic stabilisation ponds are most widely used to treat abattoir wastewater and its efficiency varies from place to place, for example, in New Zealand, the ponds remove less than 35 % of N [36].

Anaerobic lagoons can be an effective wastewater treatment technology, for its ability to reduce BOD 97%, COD 95% and SS 96 % [37]. Hence, it is considered as the best available treatment technology for the slaughterhouse wastewater, since meat industry wastewater is rich in organic pollutants [38,39]. This method is most popular in countries like USA and Australia mainly because they have suitable climate and large land availability to adopt anaerobic lagoons in wastewater treatment [34]. In meat industry wastewater, N and P can be removed biologically using granular sludge method, with a removal efficiency of TN-86 %, TP-74 % and COD-68 % [40].

Nutrient removal is an important treatment process in slaughterhouse wastewater treatment and is the final or tertiary stage treatment. Nutrients such as N and P are introduced to the receiving area if industries fail to adopt nutrients removal before discharge into sites. Majority of the industries reuse their wastewater for various purposes especially irrigating the crops/ lawn. Environmental factors of an effective treatment system are shown in figure 3.This helps to maintain soil fertility, productivity and sustainability whereas discharge into river, ocean need an appropriate nutrient removal techniques to reduce the nutrients concentrations to minimum acceptable level. Advanced treatment processes (Granulated sludge, Sequencing batch reactors, integrated aerobic-anaerobic film reactor, Aerobic-anaerobic stabilisation pond, Anaerobic treatment methods) helps to reduce the concentration of nutrients in the effluent, most essentially N and P. Eco toxicity level of the wastewater quality standards and their usage are summarised in the Table 3.

(Source: MLA-RPDA-1998); a) Typical for non-potable reuse.

**Table 3.** Abattoir wastewater disposal quality

ated in the form of its merits and demerits by economic feasibility, technical availability, and socio–cultural acceptability. This kind of evaluation is very important to assume the waste‐

Abattoir wastewater

 *Trickling filter Activated sludge process Lagoons & wetlands Extended aeration Oxidation ditches Sequential Batch Reactors*

Removal of *Suspended solids Biodegradable organics Volatile organics Some nutrients (N & P)*

Recycled water

Pre-treatments include screening, catch basins, floatation, equalization, and settlers. A primary treatment includes screening, dissolved air flotation (DAF) and flow equalisation [30]. Pretreatments are processes that remove gross solids; coarse suspended floating matter and primary treatments remove readily settleable solids, most commonly by sedimentation [31]. Pre-treatment methods can be used to minimise the organic load and BOD in the wastewater. Pre-treatment methods such as screening and sedimentation helps to reduce 60% of solids and 25-35 % of BOD load from wastewater [32]. Anaerobic process includes lagoons, anaerobic contact anaerobic filter, anaerobic sequencing batch reactor (ASBR), up-flow anaerobic sludge blanket (UASB). An aerobic system includes aerated lagoons, activated sludge process, oxidation ditches, sequencing batch reactors and trickling filters. The advantage of lagoons in the wastewater treatments is high efficiency in organic material (BOD₅) removal, at the same

The pollutants that remain after primary treatments can be removed by secondary treatment methods, including fine suspended solids, colloidal and dissolved organic matter by biologi‐ cal / chemical treatment by aerobic or anaerobic process. Anaerobic contact reactors (ACR) are the best treatment system that reduces the BOD levels by 90% and volatile solids removal by 41-67 %. The issue with anaerobic reactors is odour generation, which can be minimised by installing synthetic floating covers on the lagoons, to avoid odour as well as to trap biogas [34]. Temperature is one of the limiting factors of anaerobic lagoon, which determine the efficiency

Treatment cost: \$ 0.3- 1 m³

Preliminary treatment Primary treatment Secondary treatment Tertiary treatment Advanced treatment

 *Flocculation Clarification Filtration (sand) Disinfection (chlorination, UV,*

*lagoons)*

 *Adsorption (activated carbon) Reverse osmosis*

> Removal of *Nutrients (N & P) Dissolved solids Heavy metals Pathogens*

*Granulated activated carbon*

 *Hydrogen peroxide filtration Denitrification Precipitation*

> Removal of *Organics Salts Ionic contaminants Pathogens*

*Ozonation*

water recycling method to current and future.

60 Irrigation and Drainage - Sustainable Strategies and Systems

 *Preliminary sediment clarifiers Dissolved aeration / floatation Chemical assisted sedimentation Settlers*

> Removal of *Suspended solids Some heavy metals*

Figure 2. Wastewater treatment methods

time very poor in N and P removal [33].

**Figure 2.** Wastewater treatment methods

 *Screening Shredding Grit removal Pre-aeration Pre-chlorination Catch basins*

 Removal of *Large floating Suspended solids Grits*

23

Figure 3. Factors influencing wastewater management plan involving phytoremediation **Figure 3.** Factor influencing wastewater management plan involving phytoremediation

#### **3. Effect of wastewater irrigation on environment and soil**

The impacts of the abattoir wastewater on the natural environment can be broadly classified into three categories viz, health and social impacts, economic impacts and ecological impacts.

#### **3.1. Health and social impacts,**

#### *3.1.1. Air pollution*

Air related problems in abattoir waste water can be caused by dust, flies and odour which will have strong impacts on the adjacent areas. Abattoirs are generally known as "dirty" due to various pollutants or dust generation activities such as rendering and slaughtering [41].

#### *3.1.2. Disease causing pathogens*

Wastewater carries diverse microbes that can contaminate the water sources [42], leading to the spread of pathogens from one place another [31]. This may lead to a wide range of diseases such as cholera, typhoid, and dysentery [43].Wastewater discharges from slaughterhouse without proper disinfection, leads to occurrence of meat based infections due to the high populations of *E. coli* and *Salmonella sp.* [44].

#### *3.1.3. Odour and noise nuisances*

23

Economic factor

Socio-cultural factor

Industry / plant factor

Figure 3. Factors influencing wastewater management plan involving phytoremediation

**3. Effect of wastewater irrigation on environment and soil**

**Figure 3.** Factor influencing wastewater management plan involving phytoremediation

Climatic factor

62 Irrigation and Drainage - Sustainable Strategies and Systems

Technical factor

**3.1. Health and social impacts,**

*3.1.2. Disease causing pathogens*

*3.1.1. Air pollution*

Wastewater

Phytoremediation

Assessing sustainable technology

Efficiency, eco-safety and feasibility

Low cost

Biomass / bioenergy harvested

Biomass – used for energy production

The impacts of the abattoir wastewater on the natural environment can be broadly classified into three categories viz, health and social impacts, economic impacts and ecological impacts.

Air related problems in abattoir waste water can be caused by dust, flies and odour which will have strong impacts on the adjacent areas. Abattoirs are generally known as "dirty" due to various pollutants or dust generation activities such as rendering and slaughtering [41].

Wastewater carries diverse microbes that can contaminate the water sources [42], leading to the spread of pathogens from one place another [31]. This may lead to a wide range of diseases Odour is a most common issue associated with abattoir wastewater [45]. Odour is a problem, if abattoir wastewater is not treated completely to control the biological oxygen demand (BOD), which may result in the anaerobic activities [34,46]. The majority of the meat industry sites reported that emitting nuisance odour and noise is a serious issue for the local community. The most common sources of odour emissions from the meat industries are:

The most common sources of noise pollution are:

#### *3.1.4. Aesthetic amenity*

Aesthetic amenity / loss of aesthetic value can be observed in majority of the industrial zones and disposal sites. It has significant impact on the loss of land value and aesthetics, ultimately reducing further urban development. Abattoir wastewater has disruption of recreational use of the waterways due to pollution, for example, odour nuisance and aesthetic amenity [46].

#### **3.2. Economic impacts**

#### *3.2.1. High cost*

Most abattoir industries are established away from the urban areas due to the cost of land and high capital requirement for waste and wastewater disposal [28]. Abattoir wastewater significantly increases the cost for wastewater treatment, disposal and reclamation of conta‐ minated sites [47].

Estimated cost disposal methods

\$1.95/kL discharge into sewer

\$1.55/kL discharged into waterways

\$0.60/kL discharged into land

Abattoir wastewater treatment and disposal requires high cost. For example, in Canada about Can\$ 0.70-1.60 / m3 and in the United States, about is US, \$20 / 0.159 m3 or US \$30-40 / m3 are being paid by the meat processing industry for the disposal of beef slaughter residues [38]. Most small and medium abattoirs do not have the tertiary and advance treatment facilities, due to high capital involved in these methods [31, 38].

#### *3.2.2. Loss of land value:*

Disposal of poorly treated and untreated wastewater in a land will reduce the value of land both by cost and productivity. Abattoir wastewater is mostly treated mechanically and also biological treatment system in ponds. Any leakage of effluents from ponds may result in serious ground water pollution due to infiltration of nitrate and phosphate [46]. Since abattoir wastewater discharges carry significant amount of pollutants their disposal to land need high investment, which may result in the loss of land value [34].

#### **3.3. Ecological impacts**

#### *3.3.1. Algal blooms or microbial blooms or toxic algae*

Disposal of abattoir wastewater without proper treatment leads to the deterioration of the water quality. Wastewater with its rich nutrient content can cause profuse growth of algae (algal blooms) that kills fish and other aquatic flora and fauna [34]. Abattoir wastewater with its rich nutrient content (nitrate and phosphate) from animal manure and various processes directly influences the growth of algae in the aquatic ecosystem. Prolific growth of algae is called as algal blooms, posing a direct threat to ecosystem.

#### *3.3.2. Soil contamination:*

Soil contamination is caused by discharges of poorly treated wastewater, which may contain heavy metals, organic compounds, inorganic compounds, soluble salts and pathogens. In the absence of effective management strategies, pollutants find pathways to enter groundwater and food chain causing serious threats to natural environment and human beings. Wastewater can be used for irrigating the crops, but the concentration of pollutants and nutrients load above threshold level will cause serious soil problems including soil salinity [48]. Inappropri‐ ate nutrient management in the wastewater system leads to deposition of excess amount of nutrients in the disposal sites and further causes potential effect on soil fertility and produc‐ tivity. Continuous discharge of abattoir effluents over the same site results in soil contamina‐ tion, thereby affecting soil biodiversity and productivity. Consequently, productive land and clean water resources are becoming scarce due to the following issues [29]:

Continuous disposal of effluent system can create a chance for ground water contamination due to nitrate leaching, and many other direct and indirect impacts can also occur [33]. Universally, land contamination is caused by industrial, mining, domestic and municipal wastes, and in Australia industries and mining are the two major sectors of soil contamination.

#### *3.3.3. Loss of biodiversity*

are

Abattoir wastewater treatment and disposal requires high cost. For example, in Canada about Can\$ 0.70-1.60 / m3 and in the United States, about is US, \$20 / 0.159 m3 or US \$30-40 / m3

being paid by the meat processing industry for the disposal of beef slaughter residues [38]. Most small and medium abattoirs do not have the tertiary and advance treatment facilities,

Disposal of poorly treated and untreated wastewater in a land will reduce the value of land both by cost and productivity. Abattoir wastewater is mostly treated mechanically and also biological treatment system in ponds. Any leakage of effluents from ponds may result in serious ground water pollution due to infiltration of nitrate and phosphate [46]. Since abattoir wastewater discharges carry significant amount of pollutants their disposal to land need high

Disposal of abattoir wastewater without proper treatment leads to the deterioration of the water quality. Wastewater with its rich nutrient content can cause profuse growth of algae (algal blooms) that kills fish and other aquatic flora and fauna [34]. Abattoir wastewater with its rich nutrient content (nitrate and phosphate) from animal manure and various processes directly influences the growth of algae in the aquatic ecosystem. Prolific growth of algae is

Soil contamination is caused by discharges of poorly treated wastewater, which may contain heavy metals, organic compounds, inorganic compounds, soluble salts and pathogens. In the absence of effective management strategies, pollutants find pathways to enter groundwater and food chain causing serious threats to natural environment and human beings. Wastewater can be used for irrigating the crops, but the concentration of pollutants and nutrients load above threshold level will cause serious soil problems including soil salinity [48]. Inappropri‐ ate nutrient management in the wastewater system leads to deposition of excess amount of nutrients in the disposal sites and further causes potential effect on soil fertility and produc‐ tivity. Continuous discharge of abattoir effluents over the same site results in soil contamina‐ tion, thereby affecting soil biodiversity and productivity. Consequently, productive land and

clean water resources are becoming scarce due to the following issues [29]:

**•** Surfactants derived from equipment cleaning-Increased alkalinity

**•** Wastewater from stabilisation pond, effluent evaporation-Increased salinity

**•** Organic / solids / manure transfer to wastewater and wetlands-Increased turbidity

due to high capital involved in these methods [31, 38].

64 Irrigation and Drainage - Sustainable Strategies and Systems

investment, which may result in the loss of land value [34].

called as algal blooms, posing a direct threat to ecosystem.

*3.3.1. Algal blooms or microbial blooms or toxic algae*

*3.2.2. Loss of land value:*

**3.3. Ecological impacts**

*3.3.2. Soil contamination:*

Discharge of untreated abattoir wastewater can cause serious threats in the receiving envi‐ ronments, altering the micro and macro environment of the receiving lands. The disposed nutrients and other pollutants can cause spatial and temporal heterogeneity in benthic populations and also preponderance of organisms such as oligochaetes and diptera which can also affect human beings [49].

Abattoir wastewater discharged into river can greatly impact the species diversity and development of aquatic organisms. The presence of high BOD will heavily impact on spatial and temporal heterogeneity of macro invertebrates [49]. Bioaccumulation and biomagnifica‐ tion of contaminants in in fishes present in abattoir effluent discharged aquatic ecosystems can affect a whole food cycle or food web and pose serious threats to the native flora and fauna [46].

#### *3.3.4. Sources of heavy metals*

Untreated wastewater discharged in landfill sites carry heavy metals which can affect the soil properties. Abattoir wastewater acts as a source of major nutrients (N and P) and micronutrients such as calcium, sodium, magnesium, sulphur and iron and trace amount of heavy metals such as cadmium, cobalt, nickel, copper and chromium [38].

#### *3.3.5. Climate change and global warming*

Meat production is a considerable source of global greenhouse gases emission (GHG), emitting methane, nitrous oxide and carbon dioxide through various stages. Livestock farming is one of the main activities responsible for GHGs emission around the globe [50]. GHGs are emitted by direct energy consumption and indirectly by feedstock production, herding, movement of animals, product transport, slaughtering, cleaning, and dressing the animal product, waste and wastewater.

Meat consumption will be high in 2020 and more consumption growth projected by 2050; predominantly in Asia and Pacific [44]. In the recent years, meat production and consumption has been increasing considerably, and predicted to peak in 2020. Global per capita meat consumption is projected to increase from 32.9 kg /rwt 2011 to 35.4 kg /rwt in 2020 [44]. A recent study at European Union states that ruminants (cows, sheep and goats) have the highest carbon footprint [50]. Total net GHGs emission of EU livestock production was estimated at 661mt of carbon dioxide equivalent (CO₂-eq) which is about 9-13 % of total GHGs emission for the EU agricultural sector; of those 23% methane, 24% nitrous oxide, 21% CO₂ (Energy use), 29% CO₂ (land use).

A considerable amount of GHGs emitted by the global animal industry, which is more than all the cars in the world together and large part of that 18 % nitrous oxide and methane

emissions; both of these gases have a far more powerful greenhouse gas effect than carbon dioxide [51]. Livestock sector accounts for 5-50% of total contribution, but it may vary from place to place [52]. The overall contribution consists of pigs-0.4%, sheep-3.4%, cattle-2.7%, and beef cattle-11.2%, which on an average emits 554kg CO₂-e/tonne hot standard carcass weight [47].

#### **4. Nutrient management in wastewater irrigated soils**

#### **4.1. Wastewater driven nutrients**

Large quantities of water are used in meat industry to wash the carcasses of the slaughtered animals and to clean the equipment's in abattoirs. The wastewater generated during these processes contain high organic loads, fat contents and concentrations of N, P and Na. Majority of the wastewater undergo primary and secondary treatments before being released into the environment. The discharged effluents can be used for irrigation as it contains free source of nutrients which potentially boosts production and also reduces fertilizer inputs. Nevertheless, proper N management is needed for this purpose to minimise possible groundwater contam‐ ination. Other environmental concerns include the increase in dissolved salts causing soil salinity or Sodicity and accumulation of P in soil. Phytoremediation can be a viable cost effective remediation technique to effectively manage nutrients in soil and prevent the water resources from contamination. By cultivating suitable plant species in the wastewater irrigated land, excess nutrients can be phytoextracted by the plants for growth. In the process, a large amount of biomass can be produced for energy generation or as a feed source for grazing animals.

#### **4.2. Nutrient cycling in wastewater irrigated soils**

Understanding of nutrient cycling in a wastewater irrigated ecosystem is necessary to avoid nutrient loss to the environment. Nitrogen cycle: The wastewater from slaughtering house contains nitrogen in organic forms; this is converted to ammonia by ammonification (NH4+). This process is enhanced by bacteria in anaerobic conditions. Ammonia further oxidised in to nitrite and nitrate by nitrification process with the help of nitrifying bacteria. At the end, nitrate converted into nitrogen gas by denitrification activity in the presence of facultative microor‐ ganisms. This is the typical N cycle in an abattoir wastewater irrigated ecosystem. Similarly, (Phosphorus cycle) P occurs as both organic and inorganic (phosphate) forms in the waste‐ water discharged from abattoir. With over 80 % of P occurring in the organic form, plant growth depends on the conversion of organic P in to inorganic forms. In general, P cycle in wastewater irrigated soils is most complicated as compared to N due the phosphate precipi‐ tation or accumulation.

#### **4.3. Nutrient budgeting**

Nutrient budget is an accounting approach combining the cumulative effects of nutrient inputs, uptake and deposited, which can help manage nutrients by identifying production goals and opportunities for improvements in nutrient use efficiency, and thus reduce the risk of off-farm nutrient impacts [53]. Nutrient budgeting for a wastewater treated ecosystem is more important than a farm nutrient budget. Wastewater from the treatment pond (open-pond treatment) can be used as irrigation water for fodder crops grown in the land treatment site. Abattoir wastewater typically contains a high concentration of nutrients, such as N 250 mg/L and P 30 mg/L. Annual nutrient loading used for the mass balance was calculated with the following equation.

Nutrient uptake=nutrient requirement per kg of biomass\* total biomass produced

Nutrient input=nutrient concentration/L \* Total amount of irrigation

The nutrient budgeting helps to minimising environmental impacts such as nutrient loss to atmosphere, leaching and overdose and efficient nutrient management for a sustainable production. Abattoir wastewater irrigation considerably increased the total dry matter yield, and nutrient uptake in soils. Dry matter production and nutrient uptake were proportional response to the rate of irrigation applied. Hence, an effective recapture all the nutrients that are discharged from agricultural industries is possible, thereby helps to meet a significant proportion of this requirement. Farm nutrient budget can be calculated using information obtained from nutrient input or wastewater irrigation rate-plant uptake – and soil test. These are the essential tools to calculate the effective nutrient budget to avoid nutrient loss to environment.

#### **4.4. Plant productivity in wastewater irrigated soils**

Abattoir wastewater irrigation considerably increases nutrient uptake in soils and the resultant total dry matter yield. Sparkling *et al* [54] noticed that wastewater irrigation significantly increases the annual and total herbage production and by up taking high N and P from soils. Similar results obtained by [55] concluded that wastewater irrigation has positive impacts on plant growth and development (crop height).

#### **4.5. Case study**

emissions; both of these gases have a far more powerful greenhouse gas effect than carbon dioxide [51]. Livestock sector accounts for 5-50% of total contribution, but it may vary from place to place [52]. The overall contribution consists of pigs-0.4%, sheep-3.4%, cattle-2.7%, and beef cattle-11.2%, which on an average emits 554kg CO₂-e/tonne hot standard carcass

Large quantities of water are used in meat industry to wash the carcasses of the slaughtered animals and to clean the equipment's in abattoirs. The wastewater generated during these processes contain high organic loads, fat contents and concentrations of N, P and Na. Majority of the wastewater undergo primary and secondary treatments before being released into the environment. The discharged effluents can be used for irrigation as it contains free source of nutrients which potentially boosts production and also reduces fertilizer inputs. Nevertheless, proper N management is needed for this purpose to minimise possible groundwater contam‐ ination. Other environmental concerns include the increase in dissolved salts causing soil salinity or Sodicity and accumulation of P in soil. Phytoremediation can be a viable cost effective remediation technique to effectively manage nutrients in soil and prevent the water resources from contamination. By cultivating suitable plant species in the wastewater irrigated land, excess nutrients can be phytoextracted by the plants for growth. In the process, a large amount of biomass can be produced for energy generation or as a feed source for grazing

Understanding of nutrient cycling in a wastewater irrigated ecosystem is necessary to avoid nutrient loss to the environment. Nitrogen cycle: The wastewater from slaughtering house contains nitrogen in organic forms; this is converted to ammonia by ammonification (NH4+). This process is enhanced by bacteria in anaerobic conditions. Ammonia further oxidised in to nitrite and nitrate by nitrification process with the help of nitrifying bacteria. At the end, nitrate converted into nitrogen gas by denitrification activity in the presence of facultative microor‐ ganisms. This is the typical N cycle in an abattoir wastewater irrigated ecosystem. Similarly, (Phosphorus cycle) P occurs as both organic and inorganic (phosphate) forms in the waste‐ water discharged from abattoir. With over 80 % of P occurring in the organic form, plant growth depends on the conversion of organic P in to inorganic forms. In general, P cycle in wastewater irrigated soils is most complicated as compared to N due the phosphate precipi‐

Nutrient budget is an accounting approach combining the cumulative effects of nutrient inputs, uptake and deposited, which can help manage nutrients by identifying production

**4. Nutrient management in wastewater irrigated soils**

weight [47].

animals.

tation or accumulation.

**4.3. Nutrient budgeting**

**4.1. Wastewater driven nutrients**

66 Irrigation and Drainage - Sustainable Strategies and Systems

**4.2. Nutrient cycling in wastewater irrigated soils**

A recent study on nutrient budget of an abattoir wastewater irrigated soil showed the effect of long term abattoir wastewater irrigation on soil fertility (Figure 4). However, growing suitable plants for fodder production and bioenergy generation can help the industry to get additional benefits. The study site covers 32 hectare (16 ha currently irrigated), and receives annually about 216 megalitre (ML) of abattoir wastewater. This wastewater contains 250 mg/ L of N and 30 mg/L of P. The land treatment site has received a total of 2025kgN/ha, 405kg P/ ha and 1350kg K/ha plus trace elements. In overall, this site was loaded with 32.4t N, 6.4 P and 21.6t of K every year. Dry matter production and nutrient uptake were proportional to the rate of irrigation applied. The rate of application at the land treatment site was 216 megalitre (ML)/ year and the total dry matter production was 110t in 2012. A total of 6t N, 1.3t P and 4.7t K respectively, was removed by herbage as nutrients uptake each year. This represents approx‐ imately 10% of that total applied.

**Figure 4.** Effect of long-term abattoir wastewater irrigation on soil fertility

#### **5. Sustainability concepts**

It is most essential that industries need to adopt various best practices / low cost technologies to reduce their water use and cost [34]. Irrigation of wastewater is a potential low-cost approach of wastewater management and can act as a good source of nutrients for infertile soil [34]. Australia, with several meat based industries need to manage the animal wastes and effluents with low cost technology [4]. The amount of organic load, N and P, and organic carbon concentration can be reduced by prior collection of manure before wash down, which will reduce effluent loading with high concentration of pollutants [24]. Phytoremediation of abattoir wastewater is a suitable technology to manage nutrients and metals [56]. Abattoir wastewater is a richest source of N and P; hence it can be treated as an alternative source of nutrients provider for poor fertile soil [56, 57]. The following steps are important for waste reduction and low –cost wastewater treatment techniques,

It is very important to ensure that "zero emission" standards of pollutants in the abattoir wastewater disposal are most satisfactory for various reuse process. Abattoir wastewater treatment system and its efficiency are directly influenced by various factors. Low cost / cost effective treatment technologies, available space / site, site sensitivity to odour, characterisation of treatment system, labour availability / mechanical energy, electrical energy / power, transport facility and climate these driving force applicable to vary in place to place [58].

#### **6. Conclusions and research needs**

**Figure 4.** Effect of long-term abattoir wastewater irrigation on soil fertility

68 Irrigation and Drainage - Sustainable Strategies and Systems

It is most essential that industries need to adopt various best practices / low cost technologies to reduce their water use and cost [34]. Irrigation of wastewater is a potential low-cost approach of wastewater management and can act as a good source of nutrients for infertile soil [34]. Australia, with several meat based industries need to manage the animal wastes and effluents with low cost technology [4]. The amount of organic load, N and P, and organic carbon concentration can be reduced by prior collection of manure before wash down, which will reduce effluent loading with high concentration of pollutants [24]. Phytoremediation of abattoir wastewater is a suitable technology to manage nutrients and metals [56]. Abattoir wastewater is a richest source of N and P; hence it can be treated as an alternative source of

**5. Sustainability concepts**

Globally re-use of wastewater has been steadily increased in the volume of water in crop production. Wastewater irrigation fulfils 1% of the Australian agricultural water demand by re-use. Wastewater acts as both water source and nutrient supplement. This is added benefit to agricultural sector especially water scarce region. This proposed sustainable concept illustrated in Figure 5, Phytoremediation of contaminated land with abattoir effluents using high biomass producing plant species can be a cost effective technology to convert contami‐ nated lands into cultivable land. Consequently the plants used not only act as remediators, but the biomass produced can also be used for energy production, paper production and feed for grazing animals. The Australian National Water Commission-2011[59] water initiative encourages various wastewater reuses and recycling research, and development programs especially cost effective technology to meet the national water demand both current and future. Wastewater reuse is an important component of sustainable water resource management, water reuse from various wastewater sources after removing the pollutants, nutrients and pathogens provide scope for water security.

**Figure 5.** Conceptual framework of an effective low cost treatment plan for abattoir wastewater

#### **Acknowledgements**

We would like to thank CRC CARE for providing funding (No <IP_ADDRESS>/12) to undertake research on Nutrient management in wastewater discharged soil.

### **Author details**

Raghupathi Matheyarasu1,2\*, Balaji Seshadri1,2, Nanthi S. Bolan1,2 and Ravi Naidu1,2

\*Address all correspondence to<EMAIL_ADDRESS>
1 Centre for Environmental Risk Assessment and Remediation, South Australia

2 Cooperative Research Centre for Contamination Assessment and Remediation of the Environment, University of South Australia, Mawson lakes, South Australia

#### **References**

**Figure 5.** Conceptual framework of an effective low cost treatment plan for abattoir wastewater

research on Nutrient management in wastewater discharged soil.

\*Address all correspondence to<EMAIL_ADDRESS>
We would like to thank CRC CARE for providing funding (No <IP_ADDRESS>/12) to undertake

Raghupathi Matheyarasu1,2\*, Balaji Seshadri1,2, Nanthi S. Bolan1,2 and Ravi Naidu1,2

1 Centre for Environmental Risk Assessment and Remediation, South Australia

Environment, University of South Australia, Mawson lakes, South Australia

2 Cooperative Research Centre for Contamination Assessment and Remediation of the

**Acknowledgements**

70 Irrigation and Drainage - Sustainable Strategies and Systems

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[49] Arimoro, F.O. and R.B. Ikomi, Response of macro invertebrate communities to abat‐ toir wastes and other anthropogenic activities in a municipal stream in the Niger Del‐

[52] Gunnarsson, S., et al. Meat production, climate change and ethics. 2011. Tribun EU.

[53] Gourley, C. J. P., Powell, J. M., Dougherty, W. J., and Weaver, D. M., Nutrient budg‐ eting as an approach to improving nutrient management on Australian dairy farms.

[54] Sparling, G. P., Barton, L., Duncan, L., McGill, A., Speir, T. W., Schipper, L. A., and Van Schaik, A., Nutrient leaching and changes in soil characteristics of four contrast‐ ing soils irrigated with secondary-treated municipal wastewater for four years. Soil

[55] Castro, E., M.P. Manas, and J.d.L. Heras, Effects of wastewater irrigation on soil properties and turf grass growth. Water Science and Technology, 2011. 63(8): p. 1678.

[56] Kanwar, R., Burns, R., Estany, J., Nogareda, C., and Rothschild, M, Environment Control and Animal Wastewater Management Systems. Adapting Animal Produc‐

[57] Bickers, P.O. and A.J. van Oostrom, Availability for denitrification of organic carbon in meat-processing waste streams. Bio resource Technology, 2000. 73(1): p. 53-58.

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## **Use of Hydrological Modeling Techniques to Evaluate, Develop and Enhance Irrigation Potential of a Humid Subtropical Watershed**

Muhammad Salik Javaid, Muhammad Shahid, Hamza Farooq Gabriel and Amjad Nabi

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/58915

#### **1. Introduction**

Water is essential and basic necessity of life. Water utilization can be categorized for domestic/municipal consumption, industrial usage and irrigation purposes, notwithstand‐ ing its necessity for ecological systems. Globally 69% of fresh water is withdrawn for agriculture purposes, 23% for industry and 8% for domestic use (J.Van.H et al 2002) [1]. Water has become a scarce natural resource whose equitable management for all socioeco‐ nomic development is essential. Irrigation is essential component for agriculture produc‐ tion and all developing countries are dependent on it. During 1997-1999 in developing countries two fifth of crops were provided by irrigated land (FAO, 2002a) [2]. Similarly during 1997-1999 in developing countries 59% of cereal production was obtained through irrigation (Burke et al, 2003) [3]. All over the world excluding Europe and North America agriculture sector is the largest user of water (FAO, 2002c) [4]. During 2000 worldwide 70% of water withdrawals and 93% of water consumption was done for agriculture whereas water consumption for industry and municipality use is elaborated in Figure 1 (FAO, 2004) [5]. Three litters of water per day are required for human body, approximately 30-300 liters per person are required for domestic use which reveals water requirement for agriculture is more as compared with human needs (FAO, 2003c) [6].

Agriculture is the backbone of Pakistan's economy, according to 2013-2014 economic survey agriculture generates 21% of total output of GDP. The livelihood of more than 67% of the country's population is linked with agriculture (Arif. M, 2004) [7]. Pakistan's water resources are under stress due to large extent of agriculture activities. To meet the crop water require‐

**Figure 1.** Water Withdrawals and Consumption (FAO, 2004)

ments scientific use of water resources is strongly needed. The present study was carried out on watersheds of Rawal Dam and Simly Dam located in Margalla hills, Pakistan. Both of these dams are the main source of municipal and irrigation water for Rawalpindi and Islamabad areas. The actual storage capacity of Rawal Dam was 47230 acre-feet when developed and its present storage capacity is 31000 acre-feet. Similarly the actual storage capacity of Simly Dam was 33000 acre-feet when developed and its present storage capacity is 32219 acre-feet.

#### **2. Methodology**

#### **2.1. Study area**

The study area comprises Rawal and Simly Dams located in Islamabad, the capital of Pakistan. The catchment areas of Rawal and Simly Dams are adjacent and located in Murree Hills. The Rawal Dam is located in Park area of Islamabad and Simly Dam is located 30 km east of Islamabad. The location map of the study area is given in Figure 2.

**Figure 2.** Location Map of Study Area (Landsat 2010).

The catchment areas of Rawal Dam and Simly Dam are contiguous and co-located as shown in Figure 2. The location of installed metrological stations i.e. Rawal Dam observatory and Murree observatory is also shown in Figure 2. The location map of Rawal Dam and Simly Dam is shown in Figure 3 and salient features of Rawal and Simly Dams are given in Table 1 and Table 2 respectively.

**Figure 3.** Location Map of Rawal Dam and Simly Dam.

ments scientific use of water resources is strongly needed. The present study was carried out on watersheds of Rawal Dam and Simly Dam located in Margalla hills, Pakistan. Both of these dams are the main source of municipal and irrigation water for Rawalpindi and Islamabad areas. The actual storage capacity of Rawal Dam was 47230 acre-feet when developed and its present storage capacity is 31000 acre-feet. Similarly the actual storage capacity of Simly Dam was 33000 acre-feet when developed and its present storage capacity is 32219 acre-feet.

The study area comprises Rawal and Simly Dams located in Islamabad, the capital of Pakistan. The catchment areas of Rawal and Simly Dams are adjacent and located in Murree Hills. The Rawal Dam is located in Park area of Islamabad and Simly Dam is located 30 km east of

Islamabad. The location map of the study area is given in Figure 2.

**Figure 2.** Location Map of Study Area (Landsat 2010).

**2. Methodology**

**Figure 1.** Water Withdrawals and Consumption (FAO, 2004)

78 Irrigation and Drainage - Sustainable Strategies and Systems

**2.1. Study area**

**Table 1.** Salient Features of Rawal Dam

**Table 2.** Salient Features of Simly Dam

#### **2.2. Meteorological conditions**

The climate of study area can be divided into four seasons as are experienced over the whole of Pakistan. These are the winter monsoon (December-February), the hot weather (March-May), the summer monsoon (June-September) and the transition period (October-November). It is summer monsoon rainstorms that give rise to the major floods. In study area Average Annual Precipitation is 1817mm, Average Annual Humidity is 61.90%, Average Annual Maximum Temperature is 16.90 °C and Average Annual Minimum Temperature is 8.7 °C (Pakistan Metrological Department).

#### **2.3. Data collection**

Rainfall data of Rawal and Simly catchment for the period 1975-2012 and 1983-2012 were respectively collected from Pakistan Metrological Department (PMD). The discharge data of Rawal Dam for the period 1975-2012 and Simly Dam for the period 1983-2012 were collected from Small Dams Organization Punjab and Capital Development Authority (CDA) respec‐ tively. The sediment data of Rawal catchment for the period 1975-2005 and sediment data of Simly catchment for period 1983-2008 were collected from Small Dams Organization Punjab and Capital Development Authority respectively. The temperature data of both catchments for the period 1975-2012 were collected from Pakistan Metrological Department.

#### **2.4. Double mass curve**

A Double Mass Curve is defined as the plot of cumulative value of one variable against the cumulative value of other quantity while the time period should be the same. The slope of the line will show the constant of proportionality between two quantities and the break in the slope of line will show the change in the proportionality constant between quantities. The Double Mass Curve can give us the significant information about the time in which changes occurred in those variables for which Double Mass Curve is plotted (Searcy and Hardison, 1960) [8]. The aim of this curve is to check the data consistency with respect to time and to detect the changes in trends by changes in the slope (Chow, 1964) [9]. (Kosmas, et al. 1997) [10], (Shahid. M, et al. 2014) [11] used Double Mass Curve for Hydrological studies. The Figure 4 is an example of double mass curve. The break in slope can be clearly observed from this figure.

**Figure 4.** Example of Double Mass Curve Analysis.

#### **3. Data analysis**

**Name of Dam Simly Dam**

Location of Dam Longitude 73o

Name of River Soan River

Catchment Area 59 sq. miles

Spillway discharge capacity 80,800 cusecs

Water supply 47 million gallons per day

The climate of study area can be divided into four seasons as are experienced over the whole of Pakistan. These are the winter monsoon (December-February), the hot weather (March-May), the summer monsoon (June-September) and the transition period (October-November). It is summer monsoon rainstorms that give rise to the major floods. In study area Average Annual Precipitation is 1817mm, Average Annual Humidity is 61.90%, Average Annual Maximum Temperature is 16.90 °C and Average Annual Minimum Temperature is 8.7 °C

Rainfall data of Rawal and Simly catchment for the period 1975-2012 and 1983-2012 were respectively collected from Pakistan Metrological Department (PMD). The discharge data of Rawal Dam for the period 1975-2012 and Simly Dam for the period 1983-2012 were collected from Small Dams Organization Punjab and Capital Development Authority (CDA) respec‐ tively. The sediment data of Rawal catchment for the period 1975-2005 and sediment data of Simly catchment for period 1983-2008 were collected from Small Dams Organization Punjab and Capital Development Authority respectively. The temperature data of both catchments

A Double Mass Curve is defined as the plot of cumulative value of one variable against the cumulative value of other quantity while the time period should be the same. The slope of the line will show the constant of proportionality between two quantities and the break in the slope of line will show the change in the proportionality constant between quantities. The Double Mass Curve can give us the significant information about the time in which changes occurred in those variables for which Double Mass Curve is plotted (Searcy and Hardison,

for the period 1975-2012 were collected from Pakistan Metrological Department.

Water Supply Tunnel Length 590 ft.

**Table 2.** Salient Features of Simly Dam

**2.2. Meteorological conditions**

(Pakistan Metrological Department).

**2.3. Data collection**

**2.4. Double mass curve**

Constructed in 1982

80 Irrigation and Drainage - Sustainable Strategies and Systems

#### **3.1. Rainfall-Runoff relationship of Rawal catchment**

The Hydrology of a region is controlled by precipitation. The annual rainfall and runoff relationship for Rawal catchment is shown in Figure 5. It can be observed in rainfall-runoff relationship of Rawal catchment that with the increase of rainfall runoff is also increasing. Annual Double Mass Curves of rainfall-runoff were plotted for Rawal catchment which are shown in Figure 6 and Figure 7. These figures show that runoff is increasing with the increase in rainfall. Figure 7 shows the Double Mass Curve and slope trend curves of Rawal catchment for 1975-1994 and 1995-2012. It is clear that for 1995-2012 slope trend curves are greater, which reveals that runoff is increasing during 1995-2012.

**Figure 5.** Annual Rainfall-Runoff Relationship of Rawal Catchment.

**Figure 6.** Annual Double Mass Curve of Rawal catchment (1975-2012).

Use of Hydrological Modeling Techniques to Evaluate, Develop and Enhance Irrigation Potential of... http://dx.doi.org/10.5772/58915 83

**Figure 7.** Rawal catchment Rainfall-Runoff Double Mass Curve (1975-1994) & (1995-2012).

#### **3.2. Runoff-Sediment relationship of Rawal catchment**

**Figure 5.** Annual Rainfall-Runoff Relationship of Rawal Catchment.

82 Irrigation and Drainage - Sustainable Strategies and Systems

**Figure 6.** Annual Double Mass Curve of Rawal catchment (1975-2012).

Rawal catchment runoff-sedimentation relationship using relevant organization data is given in Figure 8 and its Double Mass Curve is given in Figure 9. It is clear from Figure 8 that sedimentation rate is increasing with the increase in runoff and in double mass curve the value of slope is greater during period 1995-2005 which reveals that sedimentation is increasing with increase in runoff.

**Figure 8.** Runoff-Sediment Relationship for Rawal Catchment (1975-2005).

**Figure 9.** Rawal catchment Runoff-Sediment Double Mass Curve (1975-1994) & (1995-2005).

#### **3.3. Rainfall-Runoff relationship of Simly catchment**

The annual rainfall and runoff relationship for Simly catchment is shown in Figure 10. It can be observed in rainfall-runoff relationship of Simly catchment from 1995-2012 there is an increase in runoff from almost the same amount of rainfall which emphasize the fact that runoff amount has increased due to land use change.

**Figure 10.** Annual Rainfall-Runoff Relationship of Simly Catchment.

Annual Double Mass Curves of rainfall-runoff were plotted for Simly catchment which are shown in Figure 11 and Figure 12. These figures show that runoff is increasing with the increase in rainfall. It is clear from the Figure 11 that with the increase in rainfall runoff is also increasing. Figure 12 shows the Double Mass Curve and Slope Trend Curves of Simly catchment for 1983-1994 and 1995-2012. It is clear from Figure 12 that slope trend curves and values of slopes from regression coefficients are greater during 1995-2012 which reveals that runoff is increas‐ ing during 1995-2012.

**Figure 11.** Annual Double Mass Curve of Simly catchment (1983-2012).

**Figure 9.** Rawal catchment Runoff-Sediment Double Mass Curve (1975-1994) & (1995-2005).

The annual rainfall and runoff relationship for Simly catchment is shown in Figure 10. It can be observed in rainfall-runoff relationship of Simly catchment from 1995-2012 there is an increase in runoff from almost the same amount of rainfall which emphasize the fact that runoff

**3.3. Rainfall-Runoff relationship of Simly catchment**

amount has increased due to land use change.

84 Irrigation and Drainage - Sustainable Strategies and Systems

**Figure 10.** Annual Rainfall-Runoff Relationship of Simly Catchment.

**Figure 12.** Simly catchment Rainfall-Runoff Double Mass Curve (1983-1994) & (1995-2012).

#### **3.4. Runoff-Sediment relationship of Simly catchment**

Simly catchment runoff-sedimentation relationship using relevant organization data is given in Figure 13 and its Double Mass Curve is given in Figure 14. It is clear from Figure 13 that during1995-2005 more sedimentation occurred as compared with sedimentation during 1982-1994. Figure 14 is Double Mass Curve which shows the value of slope is greater during period 1995-2012 which reveals that more sedimentation occurred during 1995-2012.

**Figure 13.** Runoff-Sediment Relationship for Simly Catchment (1983-2012).

**Figure 14.** Simly catchment Runoff-Sediment Double Mass Curve (1975-1994) & (1995-2012).

#### **3.5. Methods practiced for irrigation in study area**

**3.4. Runoff-Sediment relationship of Simly catchment**

86 Irrigation and Drainage - Sustainable Strategies and Systems

**Figure 13.** Runoff-Sediment Relationship for Simly Catchment (1983-2012).

**Figure 14.** Simly catchment Runoff-Sediment Double Mass Curve (1975-1994) & (1995-2012).

Simly catchment runoff-sedimentation relationship using relevant organization data is given in Figure 13 and its Double Mass Curve is given in Figure 14. It is clear from Figure 13 that during1995-2005 more sedimentation occurred as compared with sedimentation during 1982-1994. Figure 14 is Double Mass Curve which shows the value of slope is greater during

period 1995-2012 which reveals that more sedimentation occurred during 1995-2012.

In Rawalpindi out of 25,000 acres an area of 820 acres are irrigated from Rawal dam and 16000 acres are irrigated by tube wells. Similarly 35 acres nurseries of CDA and private farms are irrigated from Simly Dam. The crops cultivated in study area are wheat, corn, maize and rice. Currently the surface (flood) irrigation methods are being used to irrigate the fields. Flood irrigation method is one of the oldest and obsolete methods for irrigation. In flood irrigation method a field is essentially flooded with water where the water submerges the soil. In flood irrigation too much care is required to avoid water losses. In flood irrigation water losses are more mostly due to seepage, runoff, deep percolation and evaporation. The flood irrigation is shown in Figure15.

**Figure 15.** Flood Irrigation Method.

The flood irrigation method is least efficient method and its efficiency is between 40-70% (Gill. A.M, 2010) [12]. Even the fruit orchards and vegetable gardens are being irrigated on the same pattern and methodology. The surface irrigation techniques (furrow, strip or basin) are really not beneficial to the crop productivity but their poor performance often results in wastage of water and at times in excessive water application. This also causes the root decay and decline in crop productivity.

In the current irrigation practices the water regulation is least under the control of the farmer. Water is applied when it is available with disregard to the crop demand and other hydrological and metrological inputs. In addition to all of this, losses due to evaporation also put a lot of stress on the system.

More regulated and controllable irrigation systems like sprinkler and drip irrigation systems are difficult to install and may not be initially viable because of exhaustive costs. However these have proved to be more efficient in water management and financially beneficial over life cycle cost analysis. A comparison of various water management practices and system efficiencies is given in Figure 16.

**Figure 16.** Water Management Efficiencies.

From Figure 16 it is clear that Drip irrigation method is most efficient. By remodeling of Rawal Dam and Simly Dam their storage capacity can be increased and by lining of the Rawal Dam Left Bank Canal seepage losses can be reduced thus increasing the velocity of water which will increase the efficiency of drip irrigation system whenever installed.

#### **4. Conclusions**

#### **5. Recommendations**

and metrological inputs. In addition to all of this, losses due to evaporation also put a lot of

More regulated and controllable irrigation systems like sprinkler and drip irrigation systems are difficult to install and may not be initially viable because of exhaustive costs. However these have proved to be more efficient in water management and financially beneficial over life cycle cost analysis. A comparison of various water management practices and system

From Figure 16 it is clear that Drip irrigation method is most efficient. By remodeling of Rawal Dam and Simly Dam their storage capacity can be increased and by lining of the Rawal Dam Left Bank Canal seepage losses can be reduced thus increasing the velocity of water which will

**a.** From Double Mass Curve analysis it can be concluded that during 1995-2012 the slope trend curves were more which shows in both Rawal and Simly Dam catchment runoff

**b.** Double Mass Curve analysis showed that in Both Rawal and Simly Dam catchment sedimentation increased with the time as the slope trend curves were more during 1995-2005 which shows more sedimentation occurred in both catchment during

increase the efficiency of drip irrigation system whenever installed.

stress on the system.

efficiencies is given in Figure 16.

88 Irrigation and Drainage - Sustainable Strategies and Systems

**Figure 16.** Water Management Efficiencies.

increased with the time.

**4. Conclusions**

1995-2005.

#### **Author details**

Muhammad Salik Javaid1 , Muhammad Shahid2 , Hamza Farooq Gabriel3 and Amjad Nabi4

1 Head of Department, Department of Civil Engineering, Abasyn University Islamabad Campus, Islamabad, Pakistan

2 Teaching Faculty at Department of Civil Engineering, Abasyn University Islamabad Cam‐ pus, Islamabad, Pakistan

3 Associate Professor at National University of Sciences and Technology (NUST), Islamabad, Pakistan

4 Principal River Engineer at Ministry of Water and Power, Islamabad, Pakistan

#### **References**

## **Water Balance of Flooded Rice in the Tropics**

### Siva Sivapalan

[3] Burke, J.J., Implementation of National Irrigation Strategies: Fuzzy Vision, Harsh Re‐ alities and Strange Bedfellows. In proceedings of Irrigation Policies: micro and mac‐

[4] Agricultural Drainage Water Management in Arid and Semi-arid areas, by K.K. Tanji

[5] Water Charging in Irrigated Agriculture: an analysis of internal experience. FAO Wa‐

[6] World Agriculture: towards 2015/2030. London, Earthscan Publications Ltd. London,

[7] Mazhar Arif, Land, Peasants and Poverty: Equitable Land Reforms in Pakistan, The

[8] Searcy, J.K and Hardison C.H., Double Mass Curves. U.S. Geological Survey, 1960,

[9] Chow, V.T., Handbook of Applied Hydrology, pp. 14-34, McGraw-Hill, New York,

[10] Kosmas, C., Danalatos, N and Cammeraat, L.H., The effect of land use in Indian Riv‐ er lagoon watershed. Journal of Hydrologic Engineering, 1997, 7(3), 245-251.

[11] Shahid M., Gabriel H.F., Nabi A., Haider S., Khan A.S, Shah A.M.S., Evaluation of Development and Land Use Change Effects on Rainfall-Runoff and Runoff-Sediment Relations of Catchment Area of Simly Lake Pakistan, Life Science Journal,2014 2(11),

[12] Mushtaq Ahmad Gill, Water Management Practices in Pakistan: Issues & Options for

& N.C. Kielen. Irrigation and Drainage Paper No. 61. Rome, FAO. 2002c

ro-economic considerations, Agadir, 2003.

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ter Reports No. 27. Rome, FAO. 2004.

Network Publications, Islamabad, 2004.

Water-Supply Paper 1541-B. pp. 66.

Productivity Enhancement, 2010.

FAO. 2003c.

1964.

11-15.

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/59043

#### **1. Introduction**

#### **1.1. Rice as a world food**

The world human population has been estimated at 7.2 billion in mid-2013 and is projected to reach 9.6 billion by 2050 [1]. There is an urgent need for current world food production levels to substantially be increased in order to avoid hunger and starvation of ever increasing human population. Rice and wheat are important sources of food for people around the world. Moreover, rice is considered as a staple food for about half of the world's population [2]. More than 56-61 per cent of the world's population lives in the Asian Region and the Asian popu‐ lation is growing at 1.8 per cent per year which adds 45-51 million more rice consumers annually [3,4]. Over 90 per cent of the world's rice is produced and consumed in the Asian Region by countries such as China, India, Indonesia, Bangladesh, Vietnam and Japan [4]. It has been estimated that rice production has to be raised by at least 70 per cent over the next three decades to meet the growing demands [5]. The demand for rice and its value-added products is growing steadily, with consumption stretching beyond Asia. For example, annual rice consumption in Australia increased from approximately 5 kg/capita to 10 kg/capita during the past nine years [6].

World rice production in 2013 accounts for 496.6 million tonnes of milled rice and only 37.3 million tonnes (i.e. 7.5% of total production) was traded between countries [7]. Australia produced 1.16 million tonnes of paddy rice in 2013 and usually exports 85% of its rice pro‐ duction to more than 60 countries around the world [8]. Irrigated rice in the world accounts for 79 million hectares (55% of the global harvested rice area) and contributes 75% of global rice production [9]. To keep pace with population growth, rice yields in the irrigated environ‐ ments must increase by 25% over the next 20 years [9]. Irrigation is the main water source in the dry season and is used to supplement rainfall in the wet season. Inefficient use of irrigation water is one of the main agronomic problems encountered where intensive rice cultivation is practiced.

© 2015 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and eproduction in any medium, provided the original work is properly cited.

#### **1.2. Features of tropical regions**

Most of the world's rice is grown in the tropics. The tropical region comprises the area between the Tropic of Cancer (23°27'N latitude) and the Tropic of Capricorn (23°27'S latitude). This region experiences tropical climate which is usually marked by hot and humid weather conditions. Vast amount of sunshine along with extremely heavy rainfall is the distinct feature of this climate. The season is marked with two wet and two dry seasons in areas close to equator. Further away from the equator, the climate becomes as monsoonal which has one wet season and one dry season. Wet seasons in the Northern Hemisphere occur during May to July and in the Southern Hemisphere during November to February [10].

The tropical regions of Australia are in the north of the country and include the equatorial and sub-tropical zones (Figure 1) which experience hot temperatures and very high relative humidity values. The wet season which is sometimes referred as the monsoon season starts in November and finishes in March next year. It is usually hot where the temperature varies between 30 and 50 degrees Celsius. Large amounts of water vapour in the atmosphere create high humidity during the wet season. Frequent flooding may occur due to heavy rain events during the wet season. The dry season starts in April and finishes in October. Low tempera‐ tures and clear skies are the main characteristics during the dry season. Average temperature in the dry season is about 20 degrees Celsius [11].

**Figure 1.** Tropical regions of Australia. Source: [12].

The tropical region in Australia covers 5 to 17 million hectares of arable soil. It is important to realise that the run-off from this region is roughly 152,000 GL and less than 6 per cent of this run-off is currently being used. In contrast, the total amount of water used for agriculture in the whole country is about 12,200 GL [13]. Therefore, it is predicted that by increasing the usage of available water resource in the tropical regions of northern Australia, it would be possible to double Australian agricultural output and make a significant contribution towards com‐ bating global hunger and supporting food security [13]. For example, suitable soil types, a warmer climate, and availability of irrigation water make the Ord River Irrigation Area in north-eastern Western Australia ideal for growing rice. Potential yields up to 14.3 t/ha have been demonstrated in this environment [14].

#### **1.3. Rice cultivation**

**1.2. Features of tropical regions**

92 Irrigation and Drainage - Sustainable Strategies and Systems

Most of the world's rice is grown in the tropics. The tropical region comprises the area between the Tropic of Cancer (23°27'N latitude) and the Tropic of Capricorn (23°27'S latitude). This region experiences tropical climate which is usually marked by hot and humid weather conditions. Vast amount of sunshine along with extremely heavy rainfall is the distinct feature of this climate. The season is marked with two wet and two dry seasons in areas close to equator. Further away from the equator, the climate becomes as monsoonal which has one wet season and one dry season. Wet seasons in the Northern Hemisphere occur during May to July

The tropical regions of Australia are in the north of the country and include the equatorial and sub-tropical zones (Figure 1) which experience hot temperatures and very high relative humidity values. The wet season which is sometimes referred as the monsoon season starts in November and finishes in March next year. It is usually hot where the temperature varies between 30 and 50 degrees Celsius. Large amounts of water vapour in the atmosphere create high humidity during the wet season. Frequent flooding may occur due to heavy rain events during the wet season. The dry season starts in April and finishes in October. Low tempera‐ tures and clear skies are the main characteristics during the dry season. Average temperature

and in the Southern Hemisphere during November to February [10].

in the dry season is about 20 degrees Celsius [11].

**Figure 1.** Tropical regions of Australia. Source: [12].

Rice belongs to the family *Gramineae* and genus *Oryza*. The genus *Oryza* comprises about twenty species distributed through tropical and subtropical regions of Asia, Africa, Central and South America and Australia. There are only two species of cultivated rice, *O.sativa* and *O.glaberrima*. *O.sativa* is a common rice widely grown in the tropical and temperate zones, and *O.glaberrima* is endemic to West Africa. Cultivars of *O.sativa* are divisible into three types or races: *Indica*, an elongated, thin and slightly flattened grain which stays separate in cooking; *Japonica*, a broad, thick, short, rounded grain which tends to soften if over-cooked; and *Javanica*, a long and sticky variety which possibly originated in Indonesia.

Rice is a remarkable semi-aquatic plant which has been cultivated for at least 8,000 years in widely different agro-climatic regions of the world. *O.sativa* grows at latitudes from 36° south in Australia to 49° north in Czechoslovakia at altitudes from sea-level to 2,400 metres in Kashmir. *O.sativa* is grown extensively in tropical and temperate regions, normally in water (lowland) but also as a dry-land (upland) crop. It is believed that rice cultivation must have begun at several different locations in Asia between 7,000 and 8,500 years before present time. *O.sativa* probably spread from India to Egypt, Europe, Africa, the Americas and Australia in that order.

First likely introduction of rice seed into southern Australian gold fields was by Chinese prospectors in the 1850s cultivating it in marshy areas or in ponds using effluent from mining. In the 1860s, a small rice industry using upland varieties and Chinese labour emerged in the northern Queensland to supply local demand in the North Queensland gold fields. In 1906, a Japanese ex-parliamentarian, Isaburo (Jo) Takasuka, began cultivating rice using Japanese (Japonica) varieties near Swan Hill in Victoria. In 1924, a commercial rice industry began around Leeton and Griffith in New South Wales.

#### **1.4. Water management of rice**

Rice requires more water than most other crops. Most rice varieties achieve better growth and produce higher yields when they are grown under flooded conditions than under aerobic conditions. In addition, the ponded water helps to suppress the weeds, especially broadleaf types. The ponded water provides protection against low night time air temperatures at some locations where the problem of cold damage to crop exists [15,16]. Paddy rice is usually grown in level basins which are flooded with water throughout most of the growing season. In general, areas of irrigated agriculture are prone to rising groundwater, waterlogging and salinity under poor irrigation practices when excess groundwater recharge rates occur. Under extreme circumstances, these negative effects may lead to loss of arable land and/or create additional crop or land management practices for which the grower may need to cover the extra costs. It is believed that flooded rice systems may have contributed to excess groundwater recharge rates at some locations [17,18].

It has been estimated that up to 62% of the world population will be facing water scarcity by 2030 [19]. Currently, there are many countries experiencing water scarcity for food production, for example, China [20]. Hence water will be a major constraint for agriculture in coming decades. The actual water availability in Asia, for example, decreased from 9.6 ML/year.capita in 1950 to 3.37 ML/year.capita in 1990, due to the increase in population [21]. In Asia, about 90% of fresh water diverted from water resources is used for agricultural purposes and more than 50% of this water is used to irrigate rice [22]. World population increase will likely further reduce the availability of water per capita in many countries. Hence, an appropriate response to water scarcity is to focus on the improvement of the overall productivity of water (i.e. the output of goods and services in physical or monetary terms per unit of water applied or consumed) to feed an ever-increasing world population.

With increasing water scarcity for irrigation, productivity of current rice production systems has to be improved substantially. Attempts have already been made at the International Rice Research Institute in Philippines to improve the water productivity of irrigated rice-based systems in Asia [23,24]. Modern rice varieties and advanced water management techniques warrant new estimations of water losses from flooded rice crops. This study reports on a water balance approach taken to determine the evaporation, transpiration and deep percolation losses from flooded rice bays in a tropical environment using a set of lysimeters and lock-up bay tests. Deep percolation under ponded rice culture should be within acceptable leakage rates and should not unduly affect growers or environmental managers in terms of rising groundwater levels, waterlogging and salinity.

#### **1.5. Water balance of rice fields**

The term 'water balance' refers to the accounting of water going into and out of an area. The quantity of water added to, subtracted from, and stored within a set volume of soil during a given period of time is considered. It is assumed that in a given volume of soil, the difference between the amount of water added *Win* to the soil and the amount of water removed *Wout* from the soil during a certain period is equal to the change in soil water content *∆W* during the same period of time [25]:

$$
\Delta W = W\_{\text{in}} - W\_{\text{out}} \tag{1}
$$

For this study, it is most appropriate to consider the water balance of the root zone per unit area of field. Thus the root zone water balance is expressed as [25]:

$$\left(\Delta S + \Delta V\right) = \left(RF + IR + UP\right) - \left(RO + DP + E + T\right) \tag{2}$$

where