Fresh water

Fresh water has very little salt. It is in many places. You can find it in rivers and lakes. It is also in snow and ice. Much of it is frozen in big ice sheets. Most plants and animals need it to live. Humans need it to survive, too. We use it for farms and homes. But we must be careful with it. It is a resource that can run out. We must keep our water clean and safe.

Fresh water is water with very little salt.

Most of the water on Earth is salty seawater. Fresh water makes up less than 3% of all water. Only 1% of that is easy for us to use. Much of our fresh water is frozen in ice sheets. About 70% of these reserves are in Antarctica.

Most plants and animals need fresh water to live. This includes most insects, birds, and mammals. Humans use fresh water for many things. We use it for drinking and washing. We also use it for farms and factories. In fact, farming uses about two-thirds of all fresh water we take from nature.

Fresh water comes from the water cycle. This is a set of steps where water moves from the land to the sky and back. Water evaporates from lakes and seas. It forms clouds and then falls as precipitation. Precipitation is a word for rain, snow, or hail. This water fills our rivers, lakes, and underground aquifers. An aquifer is a place underground that holds water in rocks. We must protect these sources from pollution to stay healthy.

Fresh water is a special kind of liquid or frozen water. It has very low amounts of dissolved salts.

This water is different from salty seawater or brackish water. It includes things like rain, snow, and melting ice. It also fills up lakes, rivers, and streams. Some fresh water stays hidden underground in places called aquifers. This water is very important for all living things. Most mammals, birds, and insects need it to stay alive. Even many plants cannot grow without it.

Nature has a way to keep fresh water moving. This way of working is called the water cycle. First, water from seas, lakes, and forests evaporates into the air. This means it turns into a gas and rises up. Then, it forms clouds in the sky. Eventually, it returns to the ground as precipitation. Precipitation can be rain, snow, hail, or sleet. This water then flows into rivers or soaks into the ground. This cycle helps replenish our water supplies over time.

Scientists study how water moves through different systems. They group fresh water habitats into three main types. Some are called lentic systems, which are still waters like ponds or lakes. Others are called lotic systems, which are running waters like rivers. There are also groundwaters that flow through rocks and aquifers. There is even a special zone called the hyporheic zone. This zone sits under large rivers and connects them to groundwater. Understanding these paths helps us manage our water better.

Fresh water is a very limited resource on our planet. It makes up less than 3% of all water on Earth. Only about 1% of that is easy for us to reach. A huge amount, about 70%, is frozen in Antarctica. Humans only extract about 3% of the available fresh water. Most of the water we use goes to agriculture. Farming uses roughly two-thirds of all fresh water taken from nature. We must be careful because this resource is finite.

We can see how fresh water connects to our daily lives. We use it for drinking, washing, and growing food. We also use it in factories and for fun. However, humans can sometimes make fresh water dirty through pollution. This makes it unsafe to drink without special treatment. Some people use technology like desalination to make fresh water. Desalination is a way to take salt out of seawater. This is a hard and expensive job to do.

Fresh water is any naturally occurring liquid or frozen water with low salt concentrations. It contains low levels of dissolved salts and other total dissolved solids. Scientists often define fresh water as having less than 500 parts per million (ppm) of dissolved salts. Some sources use higher limits, such as 1,000 ppm or 3,000 ppm. This water is distinct from seawater and brackish water. It is a finite but renewable natural resource. It is essential for the survival of most living organisms on Earth.

The water cycle is the mechanism that replenishes fresh water. First, water from seas, lakes, forests, and rivers evaporates into the atmosphere. This water then forms clouds. Eventually, it returns to the land as precipitation. Precipitation includes rain, snow, hail, sleet, and graupel. Once it hits the ground, it becomes surface runoff or soaks into the earth. This process moves water through various stages to create inland bodies of water. This cycle ensures that fresh water is constantly moving and being replaced.

Fresh water exists in several distinct systems. Scientists classify fresh water habitats into three main types. Lentic systems are still waters, such as ponds, lakes, swamps, and mires. Lotic systems are running-water systems, like rivers and streams. Groundwater flows through rocks and aquifers beneath the surface. There is also a hyporheic zone that bridges these systems. This zone underlies many large rivers and connects them to groundwater. It can contain much more water than the open river channel itself.

Most of the Earth's fresh water is not easily accessible. Fresh water makes up less than 3% of the world's total water resources. Of that small amount, only 1% is readily available for use. About 70% of the world's fresh water reserves are frozen in Antarctica. This includes ice sheets, ice caps, glaciers, and icebergs. Surface water, such as lakes and rivers, makes up less than 0.01% of all fresh water. Much of the rest is stored as groundwater in the saturated zone. This is the area below the water table where all spaces are filled with water.

Humanity relies heavily on these limited resources. Agriculture is the largest consumer, using roughly two-thirds of all extracted fresh water. Humans also use water for industrial, household, and recreational activities. However, much of the fresh water on Earth is not potable. Potable water is water that is safe for humans to drink. Much of our surface and groundwater requires treatment to be safe. Without treatment, it may be unsuitable for human consumption. We must manage these supplies carefully to avoid water scarcity.

Fresh water can be impacted by both natural and human processes. Erosion is a natural process that can cause pollution. Human activities can also pollute water, reducing its availability. In some areas, people use "fossil water" from deep underground aquifers. These aquifers formed hundreds of thousands or millions of years ago. Because they are not appreciably replenished today, they are essentially non-renewable. This makes them similar to resources like peat or lignite. Other technologies like desalination can create fresh water from the sea. However, desalination is a niche application due to high capital and energy costs.

Understanding water distribution is vital for global sustainability. The United Nations has set goals to protect these resources. The Sustainable Development Goals include targets for clean water and sanitation. Target 6.4 aims to increase water-use efficiency by the year 2030. Target 15.1 focuses on the conservation of inland freshwater ecosystems. These include forests, wetlands, mountains, and drylands. Protecting these systems helps ensure that water remains available for all life.