Water resources

Water resources are natural sources of water that people use for important things, like drinking and growing food. They come from places such as rivers, lakes, and underground water, or from treated water made safe for use. Most of the water on Earth is salt water, but only a small part is fresh water that people can drink. Much of this fresh water is stored in glaciers and ice caps, with some also found underground.

People need water for many daily activities, such as farming, cleaning, and making things. But water resources have many challenges. There are problems like not enough water, pollution, and changes in weather patterns that make water harder to find. Even though fresh water can renew itself, the amount of water stored underground is getting smaller in many places around the world.

Natural sources of fresh water

Further information: Water distribution on Earth

Natural sources of fresh water include surface water, under river flow, groundwater and frozen water.

Surface water

Main article: Surface water

Lake Chungará and Parinacota volcano in northern Chile

Surface water is found in rivers, lakes, and fresh water wetlands. It comes from precipitation and goes away through flow to the oceans, evaporation, evapotranspiration, and groundwater recharge. The amount of water depends on how much is stored in lakes, wetlands, and artificial reservoirs, and how the land lets water flow.

People can change surface water by building reservoirs or draining wetlands. They can also change how fast water flows by covering land with pavement or moving streams.

Natural surface water can be brought in from another area through a canal or pipeline.

Brazil has the most fresh water in the world, followed by Russia and Canada.

Water from glaciers

Glacier melt is also surface water. The Himalayas have large areas of glaciers and frozen ground. Many big rivers in Asia start there, and over a billion people depend on them. But temperatures in this region are rising faster than average, which can affect water supply.

Groundwater

Under river flow

In rivers, the total amount of water moving downstream includes water flowing through rocks and sediments below the river and its floodplain, called the hyporheic zone. For many rivers in large valleys, this hidden flow can be larger than the visible flow. This area helps exchange water between rivers and groundwater, which is important, especially in karst areas with many caves and underground rivers.

Artificial sources of usable water

There are several ways to get fresh water that people make. One way is to clean and reuse water that has already been used, called treated wastewater or reclaimed water. Another way is to get fresh water from the sea using special tools, called desalinated seawater. We also have machines that can pull water from the air, called atmospheric water generators.

Schematic illustration of a proposed approach for capturing moisture above the ocean surface and transporting it to proximal land for improving water security

Scientists are always looking for new ideas to help us get more water. Some have talked about catching water from the air above oceans. Others have thought about small, solar-powered machines that can get water from the air, but these might not always be the best long-term solution.

Water uses

Total renewable freshwater resources of the world, in mm/year (1 mm is equivalent to 1 L of water per m2) (long-term average for the years 1961–1990). Resolution is 0.5° longitude x 0.5° latitude (equivalent to 55 km x 55 km at the equator). Computed by the global freshwater model WaterGAP.

The amount of water available is very important. Some places need lots of water only part of the year. For example, farms need a lot of water in the spring but almost none in the winter. Other places, like power plants, need water all the time for cooling.

About 8% of the world’s water is used in homes. This water is for drinking, bathing, cooking, flushing toilets, cleaning, laundry, and gardening. Experts say each person needs about 50 liters of water a day for these things, not counting water for gardens.

Many people still don’t have safe drinking water. Some drink water straight from lakes and streams, which can be unsafe. Not having clean water can make people very sick.

Challenges and threats

Water is very important for life, but we face some big challenges in using it properly. One big problem is that in many places, there isn’t enough fresh water for everyone who needs it. This is called water scarcity.

Another issue is water pollution, where harmful substances get into our water supplies and make them unsafe to use. Climate change also affects water resources, changing weather patterns and the water cycle. Additionally, many areas are using more groundwater than natural processes can replace, which can harm ecosystems that depend on groundwater.

Further information: Effects of climate change on the water cycle

Water resource management

Water resource management is about making good plans to use water wisely. It means deciding how to share and care for water to meet many needs. This is part of managing the water cycle. As the world changes with climate change, managing water becomes more difficult. New ways of working together are being used to help make better choices about water.

Global values of water resources and human water use (excluding Antarctica). Water resources 1961-90, water use around 2000. Computed by the global freshwater model WaterGAP.

Good water management tries to balance everyone’s needs for water, like drinking and farming. It also aims to make sure water use is fair and lasting. One big goal is to improve water management worldwide by 2030, as part of the United Nations' efforts for sustainable development.

Sustainable water management

Only a small amount of the world’s fresh water is easy for people to use. Demand for water for drinking, making things, fun, and growing food keeps growing. Because there isn’t much fresh water available, it’s important to use what we have carefully and try not to harm the environment.

Typical urban water cycle depicting drinking water purification and municipal sewage treatment systems

Sustainable water management means thinking of water as part of nature and using it carefully. This includes ideas like including everyone in decisions about water and knowing that water is valuable. These ideas have guided water laws and practices in many countries since 1992.

Integrated water resources management

Integrated water resources management (IWRM) is a way to manage water by thinking about land, people, and the environment together. It aims to make sure everyone has fair access to water, that using water helps as many people as possible, and that nature is protected. IWRM became popular in the late 1900s and early 2000s as a better way to manage water. It brings together ideas from different people and fields to find solutions that are good for everyone and for the planet.

By country

Water resource management and governance change from country to country. For example, in the United States, the United States Geological Survey (USGS) and its partners watch over water resources. They do research and tell the public about groundwater quality. Water resources in specific countries are described below: