Rain water flows down the hills in the form of small streams which join together to form rivers and lakes. And this is the important and the natural source of water for the living beings. Some of the rain water percolates down the earth until it reaches the hard surface.
There it collects to form a large underground water reservoir. Such water is obtained on digging wells and it is called sub-soil water or ground water. Thus, there are three important natural sources of water besides abundantly available sea water. The sea water being saline cannot be sued as such either for industries or for domestic consumption.
(a) Rain water or snow water.
(b) Surface water (river, lakes, streams, canals, ponds, etc.)
(c) Ground water or sub-soil water wells and springs.
Nature has its own systems of recharging groundwater. In forests water seeps gently into the ground as vegetation breaks the fall and flow of water. This groundwater in turn feeds wells, ponds, lakes and rivers. Protecting the forests, therefore, means protecting catchment areas. However, with the cutting down of trees, these systems are being hindered.
In urban areas, the construction of houses, roads and footpaths has left little exposed parts of earth for water to soak in. Most of the water, therefore, runs wastefully through drains. In rural areas, the water quickly takes the form of flood and flows into rivers which dry up as soon as the rain stops as the bulk of water flows away. If this water can be held back, it can seep into the ground and recharge the groundwater supply.
Rainwater harvesting has become a very popular method of conserving water, particularly in the urban areas. Collecting rainwater on the roofs of building and storing it underground for later use has several advantages.
A sample urban installation of roof rainwater collection in a metropolitan city can be like this: If you live in a single dwelling unit or a multi-tenant apartment complex you already...