Rain is Nature's boon to the entire humanity.
Every drop of rain water that falls on the
ground is like a pearl. It brings relief to the
dry land and replenishes the ground water. In a
developing country like India where people are
suffering from water scarcity, rain water can be
used to solve this problem through rain water
Harvesting of rain water is the collection of rainwater into any natural resource like lake, pond, etc. or any man-made resources for its future usage for crop harvesting, toilet, gardening, etc. It is also used for replenishing the underground water. The easiest and the most common rain water harvesting method is the rooftop harvesting. With the help of this technique one can collect huge volumes of clean rain water during the rainy season and use it for different household purposes like livestock, gardening and irrigation.
Rainwater collection systems are available in different shapes and sizes. It ranges from simple catchment system under a downspout to large underground and/or above cisterns with complex filtration systems that can store huge volumes of water. Most rainwater collection systems comprise the following basic components:
Catchment surface: This is a rooftop or other raised solid surface. The good quality catchment systems have smooth, hard surfaces such as metal concrete or roofs areas. Besides the quantity of rainfall, the amount of water harvested greatly depends on the size of the surface and the incline of the catchment area.
Gutters and downspouts: They are also referred to as distribution systems. They channel water from the catchment area to a holding container such as a cistern, barrel or planted area.
Roof washers: These are devices that divert the "first flush" of rain before it enters the storage tank. It is always recommended that the "first flush" of water is diverted to an outside area of the storage system as debris, bird droppings and other toxic waste may accumulate at the catchment surface.
Leaf screens: These are screens that catch or remove debris.
Storage tank: This is the most expensive part of a rainwater harvesting system. Storage tank can be underground or aboveground and is available in numerous styles and types. It should be made opaque to thwart the growth of algae. The tank should be positioned on an elevated area to harness the advantage of gravity flow. It should be placed close to the supply line and area of use to minimise the distance over which the water is to be delivered.
Purification/treatment system: This is required for potable systems to make the water safe for consumption.
Delivery systems: These are generally pumped or gravity-fed to the landscape or other end-use areas.
Need for rain water harvesting
This technique will help in preserving more water by preventing the surface water runoff during the monsoon. Harvesting of rain water helps in improving the water quality in aquifers and reducing the soil erosion. Recharge of rainwater to the ground helps in diluting nitrates, fluorides and salinity content of the groundwater. In coastal areas recharge of rainwater avoids sea-water immersion into the fresh water bodies. Harvesting of rain water helps in curtailing the water supply bills and in minimizing the insecurity of the water requirement of the households in the rural areas. It also helps in controlling urban flooding. It reduces people's demand for water from the municipality. This in turn reduces the energy consumption in distributing water supply throughout the city.
Implementation of rainwater collection systems
Rain water harvesting plays an important role in improving the ground water table in both indirect and direct manner for at least four to six months. This technique is very effective in the desert regions and hilly regions which always regularly face water scarcity. It is for this reason the government of our country has given prime importance to this form of water harvesting system. Several awareness programmes have been launched at the village level to educate the people about the benefit of rainwater collection technique. Tamil Nadu is the first Indian state where harvesting of rainwater has been made mandatory by the state government. On 30th of May 2014, Tamil Nadu state government has declared to set up approximately 50,000 rainwater collecting systems at numerous places in Chennai. Till date, about 4,000 temples in Tamil Nadu have rain water tanks that are setup to cater to various rituals in the temples.
Even though rain water harvesting is quite expensive during the initial stages its benefits are manifold. It is one of the clean and non-polluting ways to preserve the natural rain water for our use in the future.