Assessment of Water Surface of Reservoirs with Varying Time and Increasing Population in Contai of West Bengal

Contai, a district of Purba Medinipur, has 79 natural reservoirs of minimum 0.01 hectare capacity. This water is utilised for irrigation and industrial purpose. The population of Contaihas been increased around 19% in last census decade. The decadal growth of population density in Contai is high compared to West Bengal. It had been also found that the perimeter and area of the water surface of these reservoirs were reducing gradually in last decade. Now with increasing population - irrigation and industrialisation has been taken place in Contai manifold. So withdrawal of water from the 79 existing reservoirs of Contai has been taken places in indiscriminate ways. But the recharge of reservoirs is very low since amount of rainfall in whole Purba Medinipur is quite less. In most of the season in 2019 here rainfall is less than 100 mm. From the present study it has been observed that annually the perimeter and surface area of such reservoirs are decreasing around 2.5% and 1.1% respectively. So abstraction is more than recharge of reservoirs. It's a little worried situation for Contai. If such an indiscriminate usage of water from reservoir for increasing irrigation and industrialisation has been taken place then reservoirs will become dry. Since rivers and canals in Purba Medinipur are almost saline prone so no alternative way of getting water for irrigation and industrialisation will be available. So it's high time to conserve the reservoirs of Contai. If irrigation and industrialisation are taking place by the withdrawal of groundwater then groundwater level will be diminished fast. According to Gyben Herzberg principle, for a half metre decline in groundwater level seawater encroaches into the mainland by 20 metres. So if water harvesting can be adapted to store water in reservoirs to supply water for irrigation and industrialisation then that can be bene!tted. The usage of water for various units from these reservoirs can also be limited.