mainland of the interior lake system. instead, the spanish crown invested millions pesos and mobilized tens of thousands of indigenous men in compulsory labor to build a tunnel and then an open cut trench to drain waters out of the basin of mexico. the spanish facilitated a series of practices, which would eventually lead to ecological destruction, including constructing dams, burning woodlands, and diverting water from lakes and canals. the desagüe was finally completed in the late nineteenth century under porfirio díaz, who contracted with british entrepreneur weetman pearson to complete the project using modern machinery to dredge a 47 km. trench. the mexican revolution of the 1910s brought sweeping changes, specifically in the area of land and social rights. in particular, the mexican constitution, passed in 1917, instituted major land reforms, including the right to communal lands, known as the ejido system. this system specifically allowed for indigenous communities to legally own traditionally communal lands to live on and work. these land rights also included the ownership of any water resources within the territory. moreover, the responsibility of water supply and sanitation was specifically designated to the federal government, a duty that was maintained for many decades post-revolution. in the second half of the 20th century, the mexican water supply and sanitation sector has undergone several changes of organization to improve its performance. 1948–1983: centralization montículo cinerítico (front) and bárcena (behind), volcanic cones on san benedicto, one of the revillagigedo islands.bárcena has existed only since 1952. since 1948, during the presidency of miguel alemán (1946-1952), responsibility for mexican urban water supply systems was vested in the ministry of water resources (secretaría de recursos hídricos – srh) under the federal government. for almost 30 years, the whole urban water organization was planned and carried out by the general water and sanitation committee within the srh. at the local level, federal water boards facilitated some local participation but actually also depended on the srh. in 1971, during the presidency of luis echeverría (1970–1976), a new committee for water supply and sanitation systems was introduced by srh facing a high increase in urban population which exceeded the centralized system's capacity to provide services. despite the creation of more specialized organizations at the national level, the federal government finally had no choice but to decentralize the services to the states and municipalities. the belief that water provision should be a gift from the federal government may be rooted in the policies of that centralization period. in 1982, the mexican economy collapsed, precipitated by the drop in oil prices, and federal government spending was severely restricted. 1983–1989: decentralization president miguel de la madrid (1982–1988), took office during the aftermath of the crash of the mexican economy. during his administration, municipalities were entrusted with providing water supply and sanitation services within the framework of a general decentralization process. at the same time, state governments were made responsible for technical and financial assistance. they were also authorized to decide about the municipalities' capacity for providing the services. most municipalities neither received the necessary financial resources nor the technical assistance to fulfill their new responsibilities. that is why in 1988 only 10 of 31 mexican states had devolved responsibility to the municipalities and where they did, service quality and efficiency usually deteriorated. 1989–1990s: creation of conagua and further decentralization ecotourism in the sierra gorda, the chuveje waterfall president carlos salinas, elected in 1988, began a significant sector reform, creating the national water commission or comisión nacional del agua (conagua) in 1989, which today remains a key player in mexican water supply and sanitation (see below). at the beginning, it was given the task of defining federal policies to strengthen service providers through technical assistance and financial resources. conagua, among other suggestions soon recommended to strengthen the decentralization process, improve the transparency of tariffs and introduce tariff autonomy, based on real costs for the service provision and free of political influence. consequently, many water laws were introduced or amended, partly following conagua's guidelines. in 1996, 21 states had transferred service provision to municipal service providers. the 2000s: proposals for new water laws a 2003 modification of the national water law envisaged the transfer of certain functions from both the federal and state levels to newly created institutions at the level of river basins, including financial decisions through the creation of a national water financial system. the provisions of the new law remain to be implemented. in 2015 the government presented a new general water law, requiring municipalities to ensure the financial sustainability of service operators. it also promotes associations of municipalities and private sector participation. furthermore, it clarifies the relationship between federal, state and municipal governments, providing a stronger role for state governments. the law is opposed by civil society groups of the platform "agua para todos", saying it benefits the mining and energy industry at the expense of farmers and city dwellers. the water operators' association aneas criticizes that the law neglects wastewater treatment and does not sufficiently address the issue of centralized decision-making and red tape. there was little consultation on the draft law and chances of it being passed before legislative elections in june 2015 are said to be low. water laws and regulation the 1917 mexican constitution sian ka'an biosphere reserve first and foremost, the constitution of mexico, which was originally established in 1917, states that all water in mexico is considered “national waters”. this sets the premises that mexico has the rights all water mexico and can do whatever it is they please with since they hold the territorial rights. the only water that is exempt from such territorial rights is rain water, specifically before it hits the ground considering it has not touched mexican land. mexico also has the rights to various natural resources similar to water such as soil, sea water created by salt mines and liquid petroleum. they also have the rights to all lagoons, natural lakes, rivers, streams, springs and other bodies of water that flow into the ocean, directly connected streams, flow in between different states, flow along borders of different countries, and extractable underground waters. the constitution also states that the nation has the right to regulate private property as social demands shift, including private bodies of water. such private land will be regulated through building new infrastructure and simulating farming and agricultural process in order to see how much water is needed all with the intent of avoid such water to be exploited or damaged. responsibility for water supply and sanitation policy and regulation waterfall blue cascade in chiapas, mexico, priorities at the national level are set through six year state development plans. the 2007-2012 national water program (programa nacional hídrico) is aimed at reaching the following: improve water productivity in agriculture improve access and quality to water supply and sanitation support integrated and sustainable water resources management in basins and aquifers improve the technical, administrative and financial development in the sector consolidate user and society participation and in this way support economic use prevent risks of meteorological phenomena evaluate the effects of climate change to the water cycle create a culture in compliance with the sector law federal policies for water and sanitation are set by the conagua, which became a well-established autonomous entity under the ministry of environment. conagua plays a key role in the sector's financial allocation. besides water supply and sanitation, it is also responsible for water resources management, irrigation, flood protection and personnel services. at the regional level, responsibility for water supply and sanitation vary among the 31 mexican states. most of them have created state water commissions (comisión estatal de agua - cea), which are autonomous entities that are usually under the authority of the state ministry of public works. most of them provide technical assistance to municipalities and some operate water distribution systems. mexico-u.s. water treaties are jointly administered by the international boundary and water commission, which was established in 1889 to maintain the border, allocate river waters between the two nations, and provide for flood control and water sanitation. once viewed as a model of international cooperation, in recent decades the ibwc has been heavily criticized as an institutional anachronism, by-passed by modern social, environmental and political issues. service provision sumidero canyon (chiapas). according to the mexican constitution responsibility for water supply and sanitation services delivery rests with 2,517 municipalities since the decentralization of 1983. however, a few states deliver services through state water companies on behalf of municipalities. in some cases, the state agencies directly provide water and sanitation services. in rural areas, water boards (juntas) are responsible for water supply. due to different policies and programs at the local level, service is provided directly by municipalities or by cooperatives, public or private utilities, which differ substantially concerning size, autonomy, performance and financial efficiency. although most providers lack political independence and financial efficiency, there are some notable exceptions that are efficiently operated. private sector participation in three mexican cities, water and sanitation services are provided by private companies as of early 2011: cancun, saltillo and aguascalientes. the concession in cancun, the largest of the three cities, is the oldest concession, awarded in 1993. as of 2011, it is held by grupo méxicano de desarrollo (gmd), which is part-owned by suez environnement from france. the privately held shares in the mixed public-private company in saltillo, set up in 2001, are held by aguas de barcelona, a spanish subsidiary of suez environnement. services in aguascalientes are provided by proactivo medio ambiente, a joint venture between veolia environnement from france and the spanish construction firm fcc for the latin american market. as of 2011, the government planned to award further water concessions beginning with san luis potosí, tijuana and tuxtla gutiérrez. a concession law that would improve the legal framework was under review by the mexican parliament as of march 2011. the state of puebla awarded a 30-year water and sanitation concession to the mexican company aguas de mexico in 2013, and in 2015 the state of veracruz created a mixed company following the model established in saltillo. efficiency the efficiency and quality of water and sanitation services vary widely, to a large extent reflecting different levels of development across the country. on average, the level of non-revenue water in mexico in 2011 was 38% according to imta and 47% according to conagua, almost twice as high as for well-run utilities. in 2011 as well, the average staff per 1,000 connections in a sample of 120 utilities was 5.3 according to imta, and 4.9 according to a different sample analyzed by conagua. financial aspects tariffs pantanos de centla (centla swamps) view of the centla, tabasco. the mexican average tariff per m3 (us$0.32) is about half of the average in latin america and the caribbean (us$0.65). however, since tariffs are fixed at the municipal level depending on different legal frameworks, they differ substantially. consequently, domestic users in tijuana monthly pay us$1.1 for 30m3, whereas customers in villahermosa only pay us$0.05 for the same amount. on average only 72% of all bills are being paid. 31% of water customers are not metered and are charged a flat rate independent of consumption. usually, commercial and industrial users are charged tariffs close to full cost recovery, whereas residential users are cross-subsidized. sanitation is normally charged as a small percentage share of the water bill. cost recovery since tariff levels and structures vary widely in mexico, some providers fully recover all costs while others do not even cover operating costs. there are no reliable figures concerning water supply and sanitation revenues in mexico. however, it seems that the sector as a whole generates a little modest cash surplus, which seems to reflect shortfalls in essential spending on maintenance and modernization rather than financial efficiency. according to conagua, total tariff collections were us$2 billion (mxp21.2 billion) in 2006. according to a 2011 estimate by imta based on a sample of 96 utilities, only 73% of the total amount of water bills was actually collected on average. investment mexican investment per capita in water supply and sanitation from 1991 to 2006 in constant us dollars of 2006 according to conagua, us$2.2 billion (mxp 28.6 billion) were invested in the sector in 2011, which is us$19 per capita. compared to the investment from 1996 to 2002,