Rainwater can be used in a number of ways after proper treatment. The water thus cleansed can be used by people for their personal use. It can also be used for recharging the groundwater. Recharging is being widely used today due to the doubts regarding the hygiene of the treated water for personal usage.
Settlement tank is a method of recharging the underground water. It is basically used to remove silt and other floating impurities from rainwater. It is an ordinary storage container with provisions for inflow of water from catchment and outflow of water to the recharge well. An unpaved bottom surface of the tank allows standing water to percolate into the soil. The rate of recharge of bore wells may not match the rate of rainfall in case of excess rainfall. The desilting chamber holds the excess amount of water till it is soaked up by the recharge structure in such conditions. The settlement chamber thus acts like a buffer in the system. Containers like masonry or concrete underground tanks, old unused tanks, prefabricated PVC or ferrocement tanks with enough capacity of storage can act as a settlement tank.
To recharge service tube wells, the rooftop runoff is not directly led into the tube well to prevent the contamination of groundwater. Rainwater is instead collected in a recharge well which acts as a temporary storage tank with a borehole, which is shallower than the water table. To prevent the caving in of soil, if the stratum is loose, the bore hole is provided with a casing pipe. To arrest the impurities, a filter chamber comprising of sand, gravel and boulders are provided.
A number of
Cochin apartments are using these methods of recharging to increase their ground water levels.
Settlement Tank and Service Tubewells
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