Water resources

Natural sources of fresh water include surface water, under river flow, groundwater and frozen water. Surface water and Parinacota volcano in northern Chile Surface water is water in a river, lake or fresh water wetland. Surface water is naturally replenished by precipitation and naturally lost through discharge to the oceans, evaporation, evapotranspiration and groundwater recharge. The only natural input to any surface water system is precipitation within its watershed. The total quantity of water in that system at any given time is also dependent on many other factors. These factors include storage capacity in lakes, wetlands and artificial reservoirs, the permeability of the soil beneath these storage bodies, the runoff characteristics of the land in the watershed, the timing of the precipitation and local evaporation rates. All of these factors also affect the proportions of water loss. Humans often increase storage capacity by constructing reservoirs and decrease it by draining wetlands. Humans often increase runoff quantities and velocities by paving areas and channelizing the stream flow. Natural surface water can be augmented by importing surface water from another watershed through a canal or pipeline. Brazil is estimated to have the largest supply of fresh water in the world, followed by Russia and Canada. Image:Sinclair Wetlands.jpg|Panorama of a natural wetland (Sinclair Wetlands, New Zealand) Water from glaciers Glacier runoff is considered to be surface water. The Himalayas, which are often called "The Roof of the World", contain some of the most extensive and rough high altitude areas on Earth as well as the greatest area of glaciers and permafrost outside of the poles. Ten of Asia's largest rivers flow from there, and more than a billion people's livelihoods depend on them. To complicate matters, temperatures there are rising more rapidly than the global average. In Nepal, the temperature has risen by 0.6 degrees Celsius over the last decade, whereas globally, the Earth has warmed approximately 0.7 degrees Celsius over the last hundred years. Groundwater Under river flow Throughout the course of a river, the total volume of water transported downstream will often be a combination of the visible free water flow together with a substantial contribution flowing through rocks and sediments that underlie the river and its floodplain called the hyporheic zone. For many rivers in large valleys, this unseen component of flow may greatly exceed the visible flow. The hyporheic zone often forms a dynamic interface between surface water and groundwater from aquifers, exchanging flow between rivers and aquifers that may be fully charged or depleted. This is especially significant in karst areas where pot-holes and underground rivers are common. == Artificial sources of usable water ==

There are several artificial sources of fresh water. One is treated wastewater (reclaimed water). Another is atmospheric water generators. Desalinated seawater is another important source. It is important to consider the economic and environmental side effects of these technologies. Wastewater reuse Desalinated water Research into other options Researchers proposed air capture over oceans which would "significantly increasing freshwater through the capture of humid air over oceans" to address present and, especially, future water scarcity/insecurity. == Water uses ==

. dams, thermoelectric power plants, which use water for cooling, ore and oil refineries, which use water in chemical processes, and manufacturing plants, which use water as a solvent. Water withdrawal can be very high for certain industries, but consumption is generally much lower than that of agriculture. Water is used in renewable power generation. Hydroelectric power derives energy from the force of water flowing downhill, driving a turbine connected to a generator. This hydroelectricity is a low-cost, non-polluting, renewable energy source. Significantly, hydroelectric power can also be used for load following unlike most renewable energy sources which are intermittent. Ultimately, the energy in a hydroelectric power plant is supplied by the sun. Heat from the sun evaporates water, which condenses as rain in higher altitudes and flows downhill. Pumped-storage hydroelectric plants also exist, which use grid electricity to pump water uphill when demand is low, and use the stored water to produce electricity when demand is high. Thermoelectric power plants using cooling towers have high consumption, nearly equal to their withdrawal, as most of the withdrawn water is evaporated as part of the cooling process. The withdrawal, however, is lower than in once-through cooling systems. Water is also used in many large scale industrial processes, such as thermoelectric power production, oil refining, fertilizer production and other chemical plant use, and natural gas extraction from shale rock. Discharge of untreated water from industrial uses is pollution. Pollution includes discharged solutes and increased water temperature (thermal pollution). Drinking water and domestic use (households) It is estimated that 8% of worldwide water use is for domestic purposes. Of those, 159 million people worldwide drink water directly from surface water sources, such as lakes and streams. Unsafe drinking water leads to 1.2 million deaths per year according to the World Bank. == Challenges and threats ==

Water scarcity Water pollution Water conflict Climate change Groundwater overdrafting The world's supply of groundwater is steadily decreasing. Groundwater depletion (or overdrafting) is occurring for example in Asia, South America and North America. It is still unclear how much natural renewal balances this usage, and whether ecosystems are threatened. == Water resource management ==

). Water resources 1961-90, water use around 2000. Computed by the global freshwater model WaterGAP. Water resource management is the activity of planning, developing, distributing and managing the optimum use of water resources. It is an aspect of water cycle management. The field of water resources management will have to continue to adapt to the current and future issues facing the allocation of water. With the growing uncertainties of global climate change and the long-term impacts of past management actions, this decision-making will be even more difficult. It is likely that ongoing climate change will lead to situations that have not been encountered. As a result, alternative management strategies, including participatory approaches and adaptive capacity are increasingly being used to strengthen water decision-making. Ideally, water resource management planning has regard to all the competing demands for 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. • 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 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." An IWRM approach aims at avoiding a fragmented approach of water resources management by considering the following aspects: Enabling environment, roles of Institutions, management Instruments. 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. 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. IWRM practices depend on context; at the operational level, the challenge is to translate the agreed principles into concrete action. Managing water in urban settings and municipal sewage treatment systems ==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: ==See also==