On a human time scale, the amount of water on the earth is fixed, for all practical purposes. There is little we can do to make more water. However, there are several ways to increase local supplies.
Seeding clouds with dry ice or potassium iodide particles sometimes can initiate rain if water laden clouds and conditions that favour precipitation are present.
Desalination of ocean water is a technology that have great potential for increasing fresh water. The common methods of desalination are distillation (evaporation and recondensation) or reverse osmosis (forcing water under pressure through a semipremeable membrane whose tiny pores allow water to pass but exclude most salts and minerals). Although desalination is still three to four times more expensive than most other sources of freshwater, it provides a welcome water supply in such places like Dubai, Oman and Bahrain where there is no other access to fresh water.
It is common to trap run off with dams and storage reservoirs and transfer water from areas of excess to areas of deficit using canals, tunnels and underground pipes.
A series of small dams or tributary streams can hold back water before it becomes a great flood. Ponds formed by these dams provide useful wildlife habitat and stock-watering facilities. Small dams can be built with simple equipment and local labour, eliminating the need for massive construction projects and huge dams.
The activity of collecting rainwater directly or recharging it into ground to improve ground water storage in the aquifer is called rain water harvesting. By rainwater harvesting the ground water can be conserved, water table depletion can be reduced and also sea water intrusion in coastal areas can be arrested. To recharge the groundwater rainwater that falls in the terrace of the buildings and in the open space around the buildings may be harvested. Roof top rain water can be diverted to the existing open / bore well. Rainwater available in the open spaces around the building may be recharged into the ground by the following simple but effective methods.
The Government of Tamilnadu leads the nation in implementing rain water harvesting programme. It has made it mandatory for all houses and buildings in the State to install rain water harvesting facility.
Sound farming and foresting practices can reduce runoff. Retaining crop residues on fields reduces flooding. Minimizing ploughing and forest cutting on steep slopes protects watersheds. Wetlands conservation preserves natural water storage capacity and aquifer recharge zones.
We could save as much as half of the water we now use for domestic purposes without great sacrifice or serious changes in our lifestyles. The use of washing machines, dish washers and low volume shower heads can reduce water loss.
Nearly half of all industrial water use is for cooling of electric power plants and other industrial facilities. By installing dry cooling systems, this could be avoided. Cooling water can be recharged, some industrial wastewater may be treated, recycled and reused.
As an individual you can conserve water by the following methods.
� Take shorter showers.
� Don't wash car and two wheelers often
� Don't allow tap run while washing hands, dishes, food or brushing your teeth unnecessarily.
� In your lawn consider planting native plants, a rock garden or some xerophytic landscaping.
� Use water conserving appliances : low - flow showers and low -flush toilets.
� Use recycled water for lawns, house plants and car washing
� Check taps for leaks