The fourth World War, some people say, will be fought for water. Now, we can't let that happen, can we? The water table is going down, and this is a growing concern for all of us...or it should be, at any rate. Now, it's hardly any use just talking about how bad the situation is, don't you agree? As we explore the possible remedies, one of them, which is quite practicable, is rain-water harvesting.
Rainwater harvesting refers to the gathering, or accumulating and storing, of rainwater.Traditionally, rainwater harvesting is practised in areas where the water supply is abundant, and has provided drinking water, domestic water, water for livestock, water for small irrigation and a way to increase ground water levels. There are many types of systems to harvest rainwater. Important systems include runoff rainwater (eg hillside run-off) and rooftop rainwater harvesting systems. The type used depends greatly on the purpose (domestic or industrial use) and to some extent also on economics and physical and human considerations. Generally speaking, rooftop rainwater systems are most used as they are also most economical (if there is more than 254 mm of precipitation a year)
Broadly rainwater is harvested for two purposes
- Storing rainwater for ready use in containers above or below ground
- Charged into the soil for withdrawal later (groundwater recharging)
Rainwater harvesting can be harvested from the following surfaces
Rooftops: If buildings with impervious roofs are already in place, the catchment area is effectively available free of charge and they provide a supply at the point of consumption.
Paved and unpaved areas i.e., landscapes, open fields, parks, stormwater drains, roads and pavements and other open areas can be effectively used to harvest the runoff. In this manner, water is collected in a larger area. This is particularly relevant in cases where the rainfall is low.
Waterbodies: Lakes, tanks and ponds can also be used to store rainwater. Such harvested rainwater can not only be used to meet water requirements of the city, it also recharges groundwater aquifers.
Stormwater drains: Most residential colonies have a proper network of stormwater drains. These drains offer simple and cost-effective means for harvesting rainwater.
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