Fresh Water Resources: Introduction, Definition and Examples

Key Concepts:

• Ocean
• Desalination
• Energy
• Minerals

Introduction: 

Earth’s fresh water is in the form of rainfall, ice sheets and glaciers. Ice sheet and glaciers are located far from the city. Hence the freshwater present in this form is not available for many people. People obtained freshwater from running water, standing water and groundwater that they use for washing, drinking, and cooking. Ocean supplies many natural resources to human beings. The ocean is the main source of food and minerals. It is also a means of transportation. 

Running water 

Many cities and towns are built near streams and rivers or any source of running water because people need continuous sources of water for their daily activities such as cleaning, drinking, washing, cooking, for schools, business, offices, etc. 

Standing water: 

Examples of standing freshwater are lakes, ponds, and reservoirs. These water bodies fill the holes present in the ground. Lakes fill deep holes whereas ponds are smaller and shallower than the lakes. Ponds are not a reliable source of fresh water for drinking, cooking, etc. 

Reservoir 

A man-made lake used to store water is called the reservoir. Reservoirs are made by constructing a dam across a river. Water gets stored behind the dam and can be used when needed. To keep the water supply clean, activities such as swimming, cleaning clothes, bathing are prohibited at many reservoirs. The water stored behind the reservoirs is measured in acre-feet. Acre foot is a unit of volume of water required to cover one acre of a surface area with around one foot depth. 

Groundwater 

Communities such as farms, homes, factories, offices, schools, etc., far from sources of freshwater can obtain water from groundwater. Water beneath the Earth surface is called groundwater. Groundwater percolates into the ground through aquifers. An aquifer is an underground layer of rock or soil that is capable of absorbing water. When it percolates through rock or soil layer, the water runs into a layer of rocks that does not absorb water. Then, the fresh water gets collected and forms a water table. The level of water table depends on the percolation of water from the Earth surface to underground. Aquifers get filled with water over a period of years. When water is used from the aquifers, it takes a long time to fill the aquifers. When underground water is very close to the surface, it is easy to use the freshwater by drilling or digging the wells into the ground. 

Watershed 

We know that when rain falls, 2/3^rd of this rainwater gets evaporated and goes back into the air and very small amount of water percolates into the grounds. The remaining rainwater goes into the river and then joins the ocean. The area of land where water drains into a particular waterbody such as river, lake, stream, or ocean is called a watershed. 

The advantage of a watershed is that it fills all water bodies such as lakes, rivers, oceans, underground water levels which are used by people. So, it is very important to conserve watersheds. Plants help to control the flow of water in a watershed. The roots grow deep into the soil and hold the plant in place. Then the soil can absorb the water that runs through mountain slopes and hills. If construction like roads, buildings are built in the watershed area or plants are cut, then there will be fewer plants to hold the flow of water. 

Sometimes, fast-flowing water enters the river more quickly than rivers can carry it. When large amounts of water pour over the water bodies through rainfall and spreads over the land area, it is called floods. Floods cause damage to the property by submerging roads, houses, etc. Changes in the watershed cause the change in the flow of water in a different direction. 

Pollution of Freshwater 

People use various kinds of chemicals for better growth of plants, crops, and lawns. They also use chemicals to kill harmful organisms for plants. Polluting waste is also produced by some industries. So, when water flows over such types of polluting materials, the flowing water carries all those pollutants and gets polluted. Polluted water gets spread through watershed and contaminates the sources of fresh water such as rivers, streams, etc. Polluted water gets percolated into the ground and pollutes the groundwater. 

Freshwater from the Ocean 

There is a lot of demand for freshwater for drinking, industry use and irrigation. It can be achieved by converting ocean water into fresh water. Freshwater supply can be increased by the process of desalination.  Desalination is the separation of fresh water from the ocean water or salt water. Desalination provides the required freshwater, but the process is expensive.  

Process of Desalination 

Distillation is one of the methods of desalination. During the process of distillation, water is heated to remove the salts. Water evaporates due to heat and the dissolved salt is left behind. The condensation of water vapor results in the formation of fresh water. But this process of evaporation needs a large amount of heat energy.  

Desalination is done by another method called freezing. When the water freezes, the first layer of ice crystals does not contain salt. The ice layer can be removed and melted to get fresh water. This entire process requires around one sixth of the energy required for distillation. 

Another method of desalination is reverse osmosis. It is a very popular method of desalinating ocean water. It consists of membranes that allow the water under high pressure to go through, but do not allow dissolved salts to pass through it.  

Ocean: Source of Mineral and Energy resources 

We know that salt is one mineral resource obtained from the sea. Apart from salt we get petroleum, nodules, and trace minerals from the ocean. 

Petroleum: 

Petroleum is the most valuable resource found beneath the sea floor. Natural gas deposits and offshore oil are present along continental margins all over the world. Around 1/4^th of the world’s oil is obtained from sea wells. New drilling techniques help to extract oil and gas  from the great sea depths. 

 

Nodules: 

Nodules are chunks of potato-shaped minerals found on the abyssal floor of the ocean. Nodules are an important source of iron, nickel, cobalt, manganese, phosphate, and copper. But the recovery of nodules is very expensive and difficult because nodules are located in very deep waters. 

Trace Minerals 

The ocean is also a source of trace minerals such as bromine and magnesium. There are many other less useful chemicals that are dissolved in the ocean. The extraction of these trace amount of minerals is very expensive. 

Food from the Ocean 

We get seafood from the ocean, which is a great source of protein. Seafood can be obtained by fishing or through aquaculture. 

Fishing: 

Fish is a major source of food for many people around the world. Hence, fishing is an important industry. But when the ocean is flooded with fish and overharvested for a long period of time, the population of fish can be reduced drastically. This reduced population of fish can damage the ecosystem. Due to this, many governments have passed laws to avoid overharvesting of fish. 

Aquaculture 

Aquaculture is the rearing of aquatic plants and animals for human consumption. Salmon, oysters, catfish, and shrimp are grown on a large scale on aquatic farms. The same methods are used to rear fish and seaweed on the ocean farms. The major problem with aquaculture is that ocean farms are prone to pollution. Sometimes ocean farms themselves become the source of pollution. Under favorable conditions, ocean farms produce large amounts of food than agricultural farms. 

Pollution of ocean water 

Oceans get polluted by dumping garbage, nuclear waste, and sewage. Till recently, pollutants used to be diluted or destroyed because they spread throughout the ocean. But due to the increase in population and the increase in the use of toxic materials, the ability of the ocean to absorb waste and renew itself has been reduced drastically. Traces of pollutants such as mercury, insecticides, DDT, and lead from gasoline have been found in the ocean. In some parts of the world, the consumption of fish becomes unsafe due to high amounts of pollutants in the water. Coastal areas and beaches are in great danger of pollution because they are close to the sources of pollution. 

Summary:

• Humans depend on natural resources because humans use natural resources as the sources of energy.
• Natural resources, such as oil, water, soil, minerals, wind, and sunlight, are distributed unevenly on the Earth’s surface.
• Resources can be changed by the movement of geologic processes.
• Earth’s fresh water is in the form of rainfall, ice sheet and glaciers.
• The examples of standing freshwater are—lakes, ponds, and reservoirs.
• Water beneath the Earth surface is called the groundwater.
• Aman-made lake used to store water is called the reservoir
• The area of land where water drains into a particular waterbody such as river, lake ,stream, or ocean is called watershed.
• Desalination is the separation of fresh water from ocean water or salt water. It provides the required freshwater.
• Distillation is one of the method of desalination.
• We get salt, petroleum, nodules, and trace minerals from the ocean.
• Water gets polluted by industrial waste, chemicals, sewer, etc.