Dear Amit, Recharge of Pond ...

Dear Amit, Recharge of Pond In places where the withdrawal of water is more than the rate of recharge an imbalance in the groundwater reserves is created. Recharging of aquifers is undertaken with the following objectives: • To maintain or augment natural groundwater as an economic resource • To conserve excess surface water underground • To combat progressive depletion of groundwater levels • To combat unfavourable salt balance and saline water intrusion Design of recharge structures and settlement tank For designing the optimum capacity of the tank, the following parameters need to be considered: 1.) Size of the catchment 2.) Intensity of rainfall 3.) Rate of recharge, which depends on the geology of the site The methodology of design of a recharge pond is similar to that for a settlement tank. The difference is that the water-holding capacity of a recharge trench is less than its gross volume because it is filled with porous material. A factor of loose density of the media (void ratio) has to be applied to the equation. The void ratio of the filler material varies with the kind of material used, but for commonly used materials like brickbats, pebbles and gravel, a void ratio of 0.5 may be assumed. Using the same method as used for designing a settlement tank: Assuming a void ratio of 0.5, the required capacity of a recharge tank = (100 x 0.025 x 0.85)/0.5 = 4.25 cu. m. (4,250 litres) In designing a recharge trench, the length of the trench is an important factor. Once the required capacity is calculated, length can be calculated by considering a fixed depth and width. Regards, Prem Baboo