RAINWATER HARVESTING
One way of increasing the availability of water to overcome its shortage is rainwater harvesting The activity of collecting rainwater directly and store it in big tanks for later use, or making the rainwater percolate into ground more efficiently to recharge the groundwater, is called rainwater harvesting. Thus there are two main techniques of rainwater harvesting:
(1) Collection and storage of rainwater in tanks for future use when there is scarcity of water, and (i) To make rainwater percolate into the ground more efficiently by constructing percolation pits and
recharge wells so as to recharge (or replenish) groundwater. The groundwater which we take out for our use by digging wells, tube wells and installing hand pumps, comes from the rainwater which seeps into the ground naturally. Now, when too much water is drawn through wells and tube-wells for use in homes, agriculture and industry, the water level in the wells and tube-wells goes down drastically. Some of the wells and tube-wells may even dry up completely. This leads to shortage of groundwater.
In rural areas (village areas), most of the ground has open soil due to which rainwater can seep into the ground naturally to make up for the loss in groundwater due to excessive use. In urban areas (city areas), however, most of the ground is covered with buildings, concrete pavements and metalled roads due to which only very little rainwater seeps into the ground naturally. Most of the rainwater which falls in cities flows into dirty water drains and goes away. So, rainwater harvesting is necessary in city areas. Rainwater harvesting by making more water percolate into the ground is usually done in those areas of a city where tube-wells for supplying water are located. This is to make sure that the tube-wells will never go dry. Rainwater harvesting can be done in two ways:
1. Rooftop rainwater harvesting, and
2. Rainwater harvesting from open spaces around buildings. We will now describe both these methods of rainwater harvesting in somewhat detail, one by one.