Water resources

Water resources are natural sources of water that people can use for many important things, like drinking and growing food. They can come from natural 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 face 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 is naturally added by precipitation and lost through flow to the oceans, evaporation, evapotranspiration, and groundwater recharge. The amount of water in any surface water system depends on many factors such as how much water is stored in lakes, wetlands, and artificial reservoirs, and how the land in the area allows water to flow.

People can change how much surface water there is by building reservoirs or by draining wetlands. They can also change how quickly water flows by covering land with pavement or changing the path of streams.

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

Brazil is thought to have the most fresh water in the world, followed by Russia and Canada.

Water from glaciers

Glacier melt is also considered surface water. The Himalayas, often called "The Roof of the World", have some of the largest areas of glaciers and frozen ground outside the poles. Many of Asia's biggest rivers start there, and over a billion people depend on them. However, temperatures in this region are rising faster than the global average, which can affect water supply.

Groundwater

Under river flow

In rivers, the total amount of water moving downstream includes not just the water you can see, but also 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 much larger than the visible flow. This area helps exchange water between rivers and groundwater, which can be very 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 are made by people. 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 at any time is very important. Some places need lots of water only part of the year. For example, many 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. In 2017, 844 million people lacked basic drinking water services. 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 there are some big challenges we face 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 or unhealthy to use. Climate change also affects water resources, altering weather patterns and the water cycle. Additionally, many areas are using more groundwater than natural processes can replace, leading to a decrease in the world’s supply of this important resource. This overuse 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 plans and decisions to use water in the best way possible. It includes planning, developing, and managing water to meet different needs. This is part of managing the water cycle. As the world changes with climate change and past decisions, managing water becomes more challenging. New strategies and ways of working together are being used to help make better decisions 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, farming, and other uses. It also aims to make sure water use is sustainable and fair. One big goal is to improve water management worldwide by 2030, as part of the United Nations' efforts for sustainable development.

Sustainable water management

Right now, only a tiny 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 wisely and try not to harm the environment.

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

Sustainable water management means looking at water as part of nature and using it carefully. This includes ideas like involving everyone in decisions about water and recognizing 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 knowledge and 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 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: