CBSE Class 10 Science 2017 · Paper 31/1/1/C · Question 24

(a) Sustainable development is development that meets the basic needs of the present generation while preserving natural resources for the needs of future generations. It is necessary because natural resources are limited while the demand for them keeps rising with the population, so unplanned use would exhaust them; because the resources have to last for the generations to come; because extracting and using them damages the environment, and that damage has to be kept in check; and because the benefits of development should reach everyone. (b) Water harvesting is the capturing of rainwater where it falls, or of its run-off, and storing it in tanks, ponds and check dams, or leading it into the ground to recharge the groundwater. Four benefits: (1) it recharges the groundwater and raises the water table, so wells are recharged; (2) water stored underground does not evaporate; (3) it spreads out and provides moisture for vegetation over a wide area; (4) it does not provide breeding grounds for mosquitoes, as stagnant water does. (It also protects the groundwater from contamination and reduces run-off and soil erosion.)