Water is essential for the sustenance of living beings on the Earth. 97% of the Earth’s surface is covered by salt water and only a small portion, 3% is available for the use of living beings. However, water is a renewable resource. It goes through the hydrological cycle to replenish itself. The natural sources of water include rivers, lakes, sea, frozen water, glaciers, groundwater, etc.
Different Water Resources
The main sources of water are snow, rain, hail, etc. Water resources can be categorized into two types- freshwater resources and marine resources.
Freshwater Resources
Freshwater, on which mankind directly depends, is exhaustible but it can be renewed by oceans through the hydrological cycle. About 90% of water evaporating from oceans returns to it while 10% remains on land to support natural and manmade ecosystems.
Sources of freshwater
Freshwater occurs in ponds, rivers, lakes, streams, and underground pools. They receive about 2.7 million cubic meters of freshwater annually through an average rainfall of 110 cm. There is a groundwater reservoir of about 27 million cubic km in our country. Rivers and groundwater are used by man for various purposes.
Natural role of freshwater
Freshwater plays several important roles in the biosphere.
- There is evidence to show that life originated in water. Water is an essential and principal component of living bodies and is vital for life processes (metabolism) as well. It forms 60-90% of cell contents in living organisms.
- It serves as a habitat for a variety of organisms including bacteria, protozoa, animals, and plants.
- It has a strong influence on climate regulation.
- Human beings use fresh water for drinking, cooking, washing, bathing, and disposal of sewage.
- Agriculture consumes the maximum amount of water. It is used for irrigation and about 50 million hectares of land in India come under irrigation
- Industries consume a large amount of water for cooling, heating, and other purposes. It is estimated that the formation of one kg of wood pulp consumes 50 L of water.
- Water is used for construction work.
- Waterfalls, tides, and river currents are used for generating energy.
- Waterways are used for transportation.
- Freshwater is used for raising fish and other aquatic animals.
Much of the water for the above purposes is obtained from rainfall and surface flow such as rivers and lakes.
Water Problems
- The rise in population and expansion of industries and the agriculture sector have increased the water demand. The average per capita consumption of water in cities is anywhere between 300-700 litres per day.
- Deforestation in the catchment areas has reduced rainwater absorption, leading to wastage of water through floods and soil erosion.
- Hard water shortens the life of utensils and appliances by causing incrustations in them.
- Rainwater may contain dissolved oxides of nitrogen and sulphur which are harmful to the plants.
- Water that has more than 3.5 gm of salt is unsuitable for irrigation thus posing a challenge to get useful water.
Marine Water Resources
Marine water is not fit for human use as it contains salt. Oceans are the largest reservoirs of water having more than 97% of total free water and 70% of the available water on the earth.
All oceans are connected. Oceans produce more biomass than land. It functions as a heat bank and helps maintain the atmospheric balance of carbon dioxide by absorbing the extra amount of this gas.
Marine water uses
- Common salt is obtained by the evaporation of seawater in salt pans that are built near the seashores.
- Edible algae such as Ulva, Caulerpa, Laminaria, Sargassum, Rhodymenia, Porphyra etc are eaten by people in several countries.
- Fishes: About 75 million tonnes of edible fish are caught from sea.
- Petroleum and natural gas have their major reservoir in the sea bed. Eg. Bombay High.
- Algal products: Agar, taken from red algae, is used as a culture medium. Algin from brown algae is used in emulsions like ice cream, paste, creams, surgical threads, flame-proof plastics, etc. Funori from red algae is used as an adhesive in sizing textiles and paper.
- Diatomite is the deposition of diatom shells which are used for the preparation of soundproofing. It is also useful as a clearing agent in visible paints.
- Pearls obtained from oysters, corals, shells from marine animals, etc are also marine resources that are used in jewelry making.
- Electricity: Ocean tides, temperature differences, and wave energy are used for generating electricity.
- Freshwater from Oceans: In many coastal areas, desalination industry plants have been installed to get fresh water from seawater.
- The ocean floor contains several polymetallic nodules called manganese nodules that have manganese, copper, nickel, and cobalt.
Problems with Ocean Water
- Over 3000 million tonnes of silt enters the sea from the land through rivers.
- Towns, villages, and industries near the coast pass effluents, sewage, and garbage into the sea, polluting it.
- About 10 million tonnes of oil gets spilled annually in oceans from extraction wells, loading and unloading of tankers, accidents, etc.
- Dumping toxic waste in sealed containers deep in the sea could lead to the leakage of these that will pollute the water.
Management and Conservation of Water Resources
Treatment of wastes: Neither dump wastes and wastewater directly in oceans nor in the river. They must be properly treated before that.
Oil spills and slits should be immediately removed by skimmers and using decomposing bacteria.
Fish catching should be regulated to prevent a reduction in fish population.
Hydroelectric Project
Water is virtually an exhaustible resource. Electricity is generated by turbines that are seen with the help of falling water. It is the most common type of non-polluting commercial source of energy. Moreover, it accounts for almost 16% of total electricity generated across the globe.
In large-sized hydropower plants, water is impounded in large reservoirs called dams. They are not only useful for preventing floods and getting a regular supply of canal water but also for the development of aquaculture.
So, there is a tendency to build larger dams. However, they tend to cause earthquakes. Dams can also cause submerged forests in the nearby areas displacing a large number of inhabitants.
Micro Hydro Electric Projects
These electric projects use small natural waterfalls in the rivers and canals to generate electricity. They do not require any huge waterfall and just need some steady flow of water.
References
- Shukla, R.S. and Chandel, P.S. (2001) Plant Ecology. S. Chand and Company Ltd., New Delhi.
- Verma, P.S., Agarwal, V.K. (1999). Cell biology genetics molecular biology evolution and ecology. New Delhi: S.Chand Co.(Pvt) Ltd.
