Water resources

Artificial sources of usable water

This refers to structured systems designed by humans for the collection, storage, treatment, and the convertion of water for human use. The purpose of this system is to help mitigate the shortage of water especially in regions where there is little to no rainfall or high demand of water. There are several artificial sources of fresh water; treated wastewater (reclaimed water), atmospheric water generators and Desalinated seawater. Other important sources includes: rainwater harvesting systems, wells, and boreholes, artificial recharge ponds, dams and reservoirs. It is important to consider the economic and environmental side effects of these technologies.

Wastewater reuse

Water reclamation is the process of converting municipal wastewater or sewage and industrial wastewater into water that can be reused for a variety of purposes. It is also called wastewater reuse, water reuse or water recycling. There are many types of reuse. It is possible to reuse water in this way in cities or for irrigation in agriculture. Other types of reuse are environmental reuse, industrial reuse, and reuse for drinking water, whether planned or not. Reuse may include irrigation of gardens and agricultural fields or replenishing surface water and groundwater. This latter is also known as groundwater recharge. Reused water also serve various needs in residences such as toilet flushing, businesses, and industry. It is possible to treat wastewater to reach drinking water standards. Injecting reclaimed water into the water supply distribution system is known as direct potable reuse. Drinking reclaimed water is not typical. Reusing treated municipal wastewater for irrigation is a long-established practice. This is especially so in arid countries. Reusing wastewater as part of sustainable water management allows water to remain an alternative water source for human activities. This can reduce scarcity. It also eases pressures on groundwater and other natural water bodies.

There are several technologies used to treat wastewater for reuse. A combination of these technologies can meet strict treatment standards and make sure that the processed water is hygienically safe, meaning free from pathogens. The following are some of the typical technologies: Ozonation, ultrafiltration, aerobic treatment (membrane bioreactor), forward osmosis, reverse osmosis, and advanced oxidation, or activated carbon. Some water-demanding activities do not require high grade water. In this case, wastewater can be reused with little or no treatment.

Desalinated water

Desalination is the artificial process by which salt water (generally sea water) is converted to fresh water. More generally, desalination is the removal of salts and minerals from a substance. It is possible to desalinate saltwater, especially sea water, to produce water for human consumption or irrigation, producing brine as a by-product.

Interest in desalination mostly focuses on cost-effective provision of fresh water for human use. Along with recycled wastewater, it is one of the few water resources independent of rainfall. As stress on the need for freshwater intensifies globally, desalination has become a key part of strategies for global water security. According to a 2019 review in Science of the Total Environment, around 95 million cubic meters per day of desalinated water is produced worldwide, and the demand for desalinated water is expected to grow significantly to help close the global water supply gap.

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.

A 2021 study proposed hypothetical portable solar-powered atmospheric water harvesting devices. However, such off-the-grid generation may sometimes "undermine efforts to develop permanent piped infrastructure" among other problems.

Water uses

The total quantity of water available at any given time is an important consideration. Some human water users have an intermittent need for water. For example, many farms require large quantities of water in the spring, and no water at all in the winter. Other users have a continuous need for water, such as a power plant that requires water for cooling. Over the long term the average rate of precipitation within a watershed is the upper bound for average consumption of natural surface water from that watershed.

Agriculture and other irrigation

Irrigation in agriculture is the practice of applying controlled amounts of water to land to help grow crops, landscape plants, and lawns. Irrigation has been a key aspect of agriculture for over 5,000 years and has been developed by many cultures worldwide. Irrigation helps to grow crops, maintain landscapes, and revegetate disturbed soils in dry areas and during times of below-average rainfall. In addition to these uses, irrigation is also employed to protect crops from frost, suppress weed growth in grain fields, and prevent soil consolidation. It is also used to cool livestock, reduce dust, dispose of sewage, and support mining operations. Drainage, which involves the removal of surface and sub-surface water from a given location, is often studied in conjunction with irrigation. Irrigation and drainage improvements are not necessarily mutually exclusive. Often both may be required together to assure sustained high-level production of crops. For a discussion of the role of drainage practices in agriculture .

Several irrigation methods differ in how water is supplied to plants. Surface irrigation, also known as gravity irrigation, is the oldest form of irrigation and has been in use for thousands of years. In sprinkler irrigation, water is piped to one or more central locations within the field and distributed by overhead high-pressure water devices. Micro-irrigation is a system that distributes water under low pressure through a piped network and applies it as a small discharge to each plant. Micro-irrigation uses less pressure and water flow than sprinkler irrigation. Drip irrigation delivers water directly to the root zone of plants. Subirrigation has been used in field crops in areas with high water tables for many years. It involves artificially raising the water table to moisten the soil below the root zone of plants.

Industries

It is estimated that 22% of worldwide water is used in industry. Major industrial users include hydroelectric 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. These include drinking water, bathing, cooking, toilet flushing, cleaning, laundry and gardening. Basic domestic water requirements have been estimated by Peter Gleick at around 50 liters per person per day, excluding water for gardens.

Drinking water is water that is of sufficiently high quality so that it can be consumed or used without risk of immediate or long term harm. Such water is commonly called potable water. In most developed countries, the water supplied to domestic, commerce and industry is all of drinking water standard even though only a very small proportion is actually consumed or used in food preparation.

844 million people still lacked even a basic drinking water service in 2017. Of those, 159 million people worldwide drink water directly from surface water sources, such as lakes and streams. One in eight people in the world do not have access to safe water. Unsafe drinking water leads to 1.2 million deaths per year according to the World Bank.

Challenges and threats

Water scarcity

Water scarcity (closely related to water stress or water crisis) is the lack of any, local or economically viably transportable, sources of fresh water resources to meet the standard water demand in a region. There are two types of water scarcity. One is physical. The other is economic water scarcity. Physical water scarcity is where there is not enough water to meet all demands. This includes water needed for ecosystems to function. Regions with a desert climate often face physical water scarcity. Central Asia, West Asia, North Africa, and most of Australia are examples of arid areas. Economic water scarcity results from a lack of investment in infrastructure or technology to draw usable water from rivers, aquifers, and other water sources. It also results from weak human capacity to meet water demand. Many people in sub-Saharan Africa are living with economic water scarcity.

Water pollution

Water pollution (or aquatic pollution) is the contamination of water bodies, which has a negative impact on how they can be used. It is usually caused by human activities. Water bodies include lakes, rivers, oceans, aquifers, reservoirs and groundwater. Water pollution results when contaminants mix with these water bodies. Contaminants can come from one of four main sources. These are sewage discharges, industrial activities, agricultural activities, and urban runoff including stormwater. Water pollution may affect either surface water or groundwater. This form of pollution can lead to many problems. One is the degradation of aquatic ecosystems. Another is spreading water-borne diseases when people use polluted water for drinking or irrigation. Water pollution also reduces the ecosystem services such as drinking water provided by the water resource.

Water conflict

Water conflict typically refers to violence or disputes associated with access to, or control of, water resources, or the use of water or water systems as weapons or casualties of conflicts. The term water war is colloquially used in media for some disputes over water, and often is more limited to describing a conflict between countries, states, or groups over the rights to access water resources. The United Nations recognizes that water disputes result from opposing interests of water users, public or private. A wide range of water conflicts appear throughout history, though they are rarely traditional wars waged over water alone. Instead, water has long been a source of tension and one of the causes for conflicts. Water conflicts arise for several reasons, including territorial disputes, a fight for resources, and strategic advantage.

Climate change

Impacts of climate change that are tied to water, affect people's water security on a daily basis. They include more frequent and intense heavy precipitation which affects the frequency, size and timing of floods. Also droughts can alter the total amount of freshwater and cause a decline in groundwater storage, and reduction in groundwater recharge. Reduction in water quality due to extreme events can also occur.^{: 558} Faster melting of glaciers can also occur.

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.

Groundwater depletion or groundwater overdrafting is the process of extracting groundwater beyond the equilibrium yield of an aquifer. Groundwater is one of the largest sources of fresh water and is found underground. The primary cause of groundwater depletion is the excessive pumping of groundwater up from underground aquifers. Insufficient recharge can lead to depletion, reducing the usefulness of the aquifer for humans. Depletion can also have impacts on the environment around the aquifer, such as soil compression and land subsidence, local climatic change, soil chemistry changes, and other deterioration of the local environment.

Water resource management

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:

1. Fresh water is a finite and vulnerable resource, essential to sustain life, development and the environment;
2. Water development and management should be based on a participatory approach, involving users, planners and policy-makers at all levels;
3. Women play a central part in the provision, management and safeguarding of water;
4. 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:

1. 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.
2. Economic efficiency: bringing the greatest benefit to the greatest number of users possible with the available financial and water resources.
3. 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.

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."

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.

Regional governance frameworks

When water systems cross international borders, countries must cooperate to manage them effectively. WHiles frameworks exist globaly, continental and regional entities often dictate policy alignment, resource allocation, and integrated management straegies. Africa usually serves as a prominent model due to its high density of transboundary waters.

Water resource management in Africa is coordinated through continental frameworks aimed at balancing development with conservation. Regional cooperation is central to continental policy because over 60 percent of Africa's water resources are contained within transboundary river basins and aquifers.

The African Ministers' Council on Water, or AMCOW, was established in 2002 via the Abuja Declaration to provide political leadership and policy direction for water and sanitation across the African Union's 55 member states. In late 2025, AMCOW formally adopted the Africa Water Vision 2063 and Policy, which replaced the previous 2025 roadmap. This updated gramework integrates water security directly into the African Union's Agenda 2063, making shared water systems as instruments for climate resilience, economic trade, and regional peace. The African Network of Basin Organisations, or ANBO also operates alongside AMCOW, coordinating technical capacity-building and standardizing data collection methodologies among Africa's scattered river basin entities.

To manage specific shared river and lake systems, African nations utilize specialized River Basin Organizations. These institutions manage competing water claims, negotiate hydrological infrastructure development like hydroelectric dams, and implement environmental protection plans.

Notable examples include the Nile Basin Initiative, a cooperative partnership formed in 1999 by the Nile riparian states. It operates as a transitional institutional mechanism to foster socio-economic benefits, and equitably utilize shared resources along the Nile River. Similarly, the Niger Basin Authority acts as one of the oldest regional water bodies on the continent, governing the Niger River basin across nine West and Central African nations. Niger Basin Authority's aim is to promote integrated development in agriculture, energy, and transport. In southern Africa, the Zambezi Watercourse Commission provides a joint governance framework for the eight riparian states sharing the Zambezi River basin, focusing heavily on equitable utilization and sustainable water infrastructure planning.

International initiatives, such as the European Union-backed Team Europe Initiative on Transboundary Water Management in Africa, provide development assistance to these organizations. They finance long-term infrastructure and update climate-resilient water allocation plans.

Managing water in urban settings

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: