CBSE Class 10 Science 2019 · Paper 31/1/1 · Question 15

Water harvesting is the technique of collecting rainwater and storing it for future use, in ponds, tanks and check dams or by letting it soak into the ground to recharge the groundwater. Two advantages at the community level: (1) water is available to the community in times of need, such as the dry season; (2) the groundwater is recharged, so the water level in wells rises. Other correct points are also valid, for example that water stored underground does not evaporate or breed mosquitoes. Two causes for the failure of sustained availability of groundwater: (1) overuse of groundwater, which is pumped out faster than the rain can recharge it; (2) deforestation, since without plant cover rainwater runs off instead of soaking into the ground. Pollution of groundwater by industrial effluents and urban wastes is another valid cause.