To use the rain-water immediately or carefully is known as `Rain water Harvesting'. We know that our only source of water is the rain-water. The lakes, ponds, wells etc. are the secondary ones. This rain water is stored in the earth's surface from ages and this water is continuously and increasingly used for different purposes. But this water is limited. After which we use the lakes, pounds, wells and later they also dry up. That is why we have to store & save water and it is the responsibility of every human being. The people from cities think that this is the duty of the government or the farmers. The land water is not enough for our increasing needs, so people have to think how the rain water can be used from their roofs and the farms where the water reaches in the land.
We have to use the water as it is. For which we use different techniques for the rain water to reach the land in more quantity.
For this the people in the urban areas should understand this & stop cutting down trees. Trees help bring the rains in quantity. So we must grow more trees.
In the beginning of rains, as the land is dry & porous, it absorbs more water. But due to surface tension, the rain water does not go deep in to the earth. Example, one sq.ft of land absorbs 1.8 litter/ hour of water. After 5 hours the same area absorbs 0.15 litter/hour .Later this absorption stops completely and water flows away from the surface. This escaping water can be stored in the deeper part of our land which has tremendous natural storage potential by proper and efficient way of Rain Water Harvesting.