Water Resources Management

No life on earth can exist without water. Scientists estimate that there is over one billion cubic kilometres of water on this earth, which covers nearly three fourths of the earth's surface in the form of oceans, rivers, lakes, snow, glaciers and groundwater. Though this seems an inordinately huge amount, in actual fact, less than one percent is fresh and usable found in lakes, ponds, rivers and groundwater. Of the remaining, 97% is found in oceans and 2% is locked up in glaciers and ice-caps. Only 1% is available for use..

Water for Life

Water is the basic necessity of life, not only for human beings, but also for plants and animals. Life began in water and it is a basic component of every living cell. Water accounts for 65% of our body weight. If we lost even 12% of it, we would die. About 83% of our blood is water. It helps digest our food, take in oxygen, transport body wastes and control body temperature. We need water in almost every domestic activity, from cooking and washing to bathing and sanitation.

Water for Climate

Water, to a large extent, determines climate. Places near large water bodies are cooler because the water bodies act as large sinks for heat, thus moderating the climate of the area. Regions near water bodies generally have milder winters and cooler summers. Water has an even more basic role in climate control through the water cycle. The evaporation of water requires huge amounts of energy, which comes from the sun. When the water vapour falls back to earth as rain, this energy is released. Thus water acts as an energy transfer and storage medium for the climate system.

Water for Agriculture and Industry

Food cannot be produced without water. Vegetables are 80-90% water and milk about 87%. Agriculture is the major consumer of water in India, accounting for nearly 93% of the total water. Almost all industrial processes need water which is needed as a solvent, as a medium, as a coolant, as a cleansing agent, etc. Water plays a very important role in disposing of waste, be it domestic sewage or industrial effluents.

Water for Power Generation

Almost all types of power generation require water - from hydel power, where falling water turns turbines to produce power, to nuclear reactors which need huge amounts of water as a coolant. In thermal power generation, next to the fuel, water is the most important resource. For the production of 1 kilowatt of electricity, thermal plants use 140 litres and nuclear plants use 205 litres of water.

Sources of Fresh Water in India

Rivers

The amount of water available for use in India is estimated as 1900 billion cubic metres per year. About 86% of this is the surface run off found in streams, rivers, lakes and ponds. In fact, these are the major sources of water in our country.

Groundwater

India is estimated to have 3,700 mhm. of groundwater, almost 10 times the annual rainfall. Only 10% of the water is being made use of at present, but with lakhs of tubewells being sunk every year to meet the growing water shortage, the water table is declining rapidly.

Tanks

Tanks are small reservoirs built by constructing earthenware dams. They have been in existence in India since ancient times when tanks were built to store rainfall. But in both British and independent India, these tanks have been sadly neglected. As a result, where tanks irrigated half the cropped area a hundred years ago, today they irrigate hardly 10% of it. In Tamilnadu, man-made earthen reservoirs are known as yeris. There are over 40,000 yeris in Tamilnadu. Their place has been taken by big dams which span the major rivers. While the Indian farmer has benefited from these huge hydel projects, and while hydro electric power is a major source of energy in India, the dams themselves have many detrimental effects on the environment.

Water Scarcity

The apparent abundance of water is deceptive and we tend to take it for granted. We tend to abuse and overuse it. This has led to water scarcity, for which the reasons are:

• Increasing demand for water due to rapid increase in population.
• Bad management: India receives the second highest amount of rainfall in the world, next only to Brazil, almost 1150 mm. annually, draining a total volume of 400 million hectare metres. Of this, only 100 million hectare metres is retained in the soil. The rest is carried as run off into the oceans and seas.
• Poor ground water resources due to deforestation and overgrazing which result in soil erosion and inability of the soil to permit water infiltration.
• Poor storage facilities.
• Over-exploitation of groundwater in water-scarce areas often resulting in the intrusion of saline sea water in coastal areas.
• Dumping of various types of pollutants into our water bodies, reducing the usability of the available water.
• Cultivation of hybrid varieties of paddy, wheat, cotton, sugarcane and tobacco which consume more water.
• Evaporational loss of water stored in large reservoirs and loss by seepage in long canal systems.
• Siltation of bodies of water due to denudation of the vegetational cover in the hills and catchment areas.

• In many parts of our country, water is scarce. In villages, women have to walk several kilometres everyday to collect a few pots of water, sometimes making several trips a day. Even in cities and towns, people face great hardships to collect a few buckets of water. With our ever-multiplying population, water scarcity is going to increase, not diminish. It is time we used our resources wisely.

Management of Water Resources

Desiltation

• Canals, tanks, yeris, etc. must be desilted regularly during the summer months.
• People should be encouraged to revive the ancient practice of protecting trees around tanks. Major rivers were sanctified and groves were established around villages and on the river banks.

Afforestation

Afforestation of barren, hilly slopes on a warfooting should be carried out. Trees withstand drought better than crops. They check dust, replenish streams, provide shade to cattle and man and give fodder for cattle. They provide innumerable uses for man. Denuding the land of trees without compensatory afforestation is a suicidal and short-sighted approach to solving immediate needs.

Ponds and Tanks

• Creation of small reservoirs and percolation tanks to hold run-off water must be implemented and maintained well.
• Agronomic practices like off-season tillage (prior to pre-monsoon showers) conserve soil moisture. Moisture penetration to a depth of 90 cm. is achieved if the land is ploughed to a depth of 30 cm. Other practices like early sowing of seeds, moderate use of fertilisers, weeding, pest and disease control and timely harvesting increase the yield inspite of limited moisture in the soil.
• Terrace cultivation of hilly slopes prevents water run-off.
• Contour ploughing and planting of grasses and trees check run-off water and increase the soil's capacity to retain moisture.
• Green manuring (incorporation of fresh green leaves into the soil) and crop-rotation (cultivating different crops in rotation depending upon the soil and climate, e.g. cereals followed by legumes) conserve soil moisture.
• Mulching the soil with organic residue conserves soil moisture.
• The use of sprinkler irrigation for closely-spaced crops like millet, pulses, groundnuts, etc., conserves 30 to 40% of the surface water.
• Drip irrigation is most suited for closely-spaced row crops like vegetables, cotton, sugarcane. The efficiency of this system is around 25 to 30% in conserving soil moisture. The cheapest and easiest form of drip irrigation is to drill one to three holes in a mud pot and bury it partially in the soil next to the plant. The water in the pot drips slowly, ensuring that the soil is continuously moist and the plant gets a constant supply of water.
• Harvesting rain water and storing it in small ponds ensures water supply during summer.
• Deep trenches can be dug adjacent to bunds to collect run off water and soil.
• All these practices are useful only if utilised properly.

Source : CPR Environmental Education Centre, Chennai