water and seeks to allocate water on an equitable basis to satisfy all uses and demands. as with other resource management, this is rarely possible in practice so decision-makers must prioritise issues of sustainability, equity and factor optimisation (in that order!) to achieve acceptable outcomes. one of the biggest concerns for water-based resources in the future is the sustainability of the current and future water resource allocation. sustainable development goal 6 has a target related to water resources management: "target 6.5: by 2030, implement integrated water resources management at all levels, including through transboundary cooperation as appropriate." sustainable water management at present, only about 0.08 percent of all the world's fresh water is accessible. and there is ever-increasing demand for drinking, manufacturing, leisure and agriculture. due to the small percentage of water available, optimizing the fresh water we have left from natural resources has been a growing challenge around the world. much effort in water resource management is directed at optimizing the use of water and in minimizing the environmental impact of water use on the natural environment. the observation of water as an integral part of the ecosystem is based on integrated water resources management, based on the 1992 dublin principles (see below). sustainable water management requires a holistic approach based on the principles of integrated water resource management, originally articulated in 1992 at the dublin (january) and rio (july) conferences. the four dublin principles, promulgated in the dublin statement are: fresh water is a finite and vulnerable resource, essential to sustain life, development and the environment; water development and management should be based on a participatory approach, involving users, planners and policy-makers at all levels; women play a central part in the provision, management and safeguarding of water; water has an economic value in all its competing uses and should be recognized as an economic good. implementation of these principles has guided reform of national water management law around the world since 1992. further challenges to sustainable and equitable water resources management include the fact that many water bodies are shared across boundaries which may be international (see water conflict) or intra-national (see murray-darling basin). integrated water resources management integrated water resources management (iwrm) has been defined by the global water partnership (gwp) as "a process which promotes the coordinated development and management of water, land and related resources, in order to maximize the resultant economic and social welfare in an equitable manner without compromising the sustainability of vital ecosystems". some scholars say that iwrm is complementary to water security because water security is a goal or destination, whilst iwrm is the process necessary to achieve that goal. iwrm is a paradigm that emerged at international conferences in the late 1900s and early 2000s, although participatory water management institutions have existed for centuries. discussions on a holistic way of managing water resources began already in the 1950s leading up to the 1977 united nations water conference. the development of iwrm was particularly recommended in the final statement of the ministers at the international conference on water and the environment in 1992, known as the dublin statement. this concept aims to promote changes in practices which are considered fundamental to improved water resource management. iwrm was a topic of the second world water forum, which was attended by a more varied group of stakeholders than the preceding conferences and contributed to the creation of the gwp. in the international water association definition, iwrm rests upon three principles that together act as the overall framework: social equity: ensuring equal access for all users (particularly marginalized and poorer user groups) to an adequate quantity and quality of water necessary to sustain human well-being. economic efficiency: bringing the greatest benefit to the greatest number of users possible with the available financial and water resources. ecological sustainability: requiring that aquatic ecosystems are acknowledged as users and that adequate allocation is made to sustain their natural functioning. in 2002, the development of iwrm was discussed at the world summit on sustainable development held in johannesburg, which aimed to encourage the implementation of iwrm at a global level. the third world water forum recommended iwrm and discussed information sharing, stakeholder participation, and gender and class dynamics. iwrm practices depend on context; at the operational level, the challenge is to translate the agreed principles into concrete action. operationally, iwrm approaches involve applying knowledge from various disciplines as well as the insights from diverse stakeholders to devise and implement efficient, equitable and sustainable solutions to water and development problems. as such, iwrm is a comprehensive, participatory planning and implementation tool for managing and developing water resources in a way that balances social and economic needs, and that ensures the protection of ecosystems for future generations. in addition, in light of contributing the achievement of sustainable development goals (sdgs), iwrm has been evolving into more sustainable approach as it considers the nexus approach, which is a cross-sectoral water resource management. the nexus approach is based on the recognition that "water, energy and food are closely linked through global and local water, carbon and energy cycles or chains." water's many different uses — for agriculture, for healthy ecosystems, for people and livelihoods — demands coordinated action. an iwrm approach is consequently cross-sectoral, aiming to be an open, flexible process, and bringing all stakeholders to the table to set policy and make sound, balanced decisions in response to specific water challenges faced. an iwrm approach focuses on three basics and aims at avoiding a fragmented approach of water resources management by considering the following aspects: enabling environment: a proper enabling environment is essential to both ensure the rights and assets of all stakeholders (individuals as well as public and private sector organizations and companies), and also to protect public assets such as intrinsic environmental values. roles of institutions: institutional development is critical to the formulation and implementation of iwrm policies and programmes. failure to match responsibilities, authority and capacities for action are all major sources of difficulty with implementing iwrm. management instruments: the management instruments for iwrm are the tools and methods that enable and help decision-makers to make rational and informed choices between alternative actions. some of the cross-cutting conditions that are also important to consider when implementing iwrm are: political will and commitment capacity development adequate investment, financial stability and sustainable cost recovery monitoring and evaluation iwrm should be viewed as a process rather than a one-shot approach - one that is long-term and iterative rather than linear in nature. as a process which seeks to shift water development and management systems from their currently unsustainable forms, iwrm has no fixed beginnings or endings. furthermore, there is not one correct administrative model. the art of iwrm lies in selecting, adjusting and applying the right mix of these tools for a given situation. managing water in urban settings typical urban water cycle depicting drinking water purification and municipal sewage treatment systems this section is an excerpt from integrated urban water management. integrated urban water management (iuwm) is the practice of managing freshwater, wastewater, and storm water as components of a basin-wide management plan. it builds on existing water supply and sanitation considerations within an urban settlement by incorporating urban water management within the scope of the entire river basin. iuwm is commonly seen as a strategy for achieving the goals of water sensitive urban design. iuwm seeks to change the impact of urban development on the natural water cycle, based on the premise that by managing the urban water cycle as a whole; a more efficient use of resources can be achieved providing not only economic benefits but also improved social and environmental outcomes. one approach is to establish an inner, urban, water cycle loop through the implementation of reuse strategies. developing this urban water cycle loop requires an understanding both of the natural, pre-development, water balance and the post-development water balance. accounting for flows in the pre- and post-development systems is an important step toward limiting urban impacts on the natural water cycle. iuwm within an urban water system can also be conducted by performance assessment of any new intervention strategies by developing a holistic approach which encompasses various system elements and criteria including sustainability type ones in which integration of water system components including water supply, waste water and storm water subsystems would be advantageous. simulation of metabolism type flows in urban water system can also be useful for analysing processes in urban water cycle of iuwm. by country water resource management and governance is handled differently by different countries. for example, in the united states, the united states geological survey (usgs) and its partners monitor water resources, conduct research and inform the public about groundwater quality. water resources in specific countries are described below: water resources by countryargentinaazerbaijanbelizeboliviabrazilchilechinacolombiacosta ricadjiboutidominican republicegyptel salvadorguatemalahondurasindiajamaicakyrgyzstanmexiconicaraguapakistanperusaudi arabiasyriauruguay