CBSE Class 10 Science 2017 · Paper 531/3 · Question 17

Water harvesting is the collection of rain water where it falls, or of the run-off of a local area, and its storage for later use, in ponds and tanks or by letting it soak into the ground to recharge the ground water. Four advantages at the community level: (i) Water is available locally even in the dry season, because harvested water fills ponds and tanks and recharges wells, raising the ground-water level for drinking and irrigation. (ii) Water stored in the ground does not evaporate; it spreads out to recharge wells and gives moisture to vegetation over a wide area, it does not provide breeding grounds for mosquitoes, and it is relatively protected from contamination by human and animal waste. (iii) The community controls its own water resource, which reduces mismanagement and over-exploitation. (iv) It helps to mitigate droughts and floods, increases crop production and the income of the community, and increases the life of the dams and reservoirs downstream.