Natural groundwater level fluctuations of Kolkata City based on seasonal field data and population growth using geo-spatial application and characterised statistical techniques

Groundwater is an important resource for any economy, excessive withdrawal of which can change the hydrological set-up leading to land subsidence and other hazardous situation in the region. With increasing population and industrialisation, the demand for water is growing and the easiest way being, tapping the groundwater resources. An effort is given to analyse the practice of groundwater level in Kolkata by studying field-based pre-monsoon and post-monsoon piezometric level data for past two decades, using GIS. The result is analysed using GIS approach applying the inverse distance weightage application. It is evident that the water level in the city fluctuates between 10 and 20 mbgl; there has been a fall of up to 5.5 m in the past decade. Exploitation of groundwater reserve has led to formation of trough which has been observed at several locations like Dumdum, Jhautala, Sinthi, Bagbazar, Jadavpur and Park Street. There has been a shift in the depletion zone from the south-central, central to northern part of the city. At few locations, there has been a lag between pre-monsoon and post-monsoon levels, which is an indication of variation in recharge and also huge abstraction. With increase in population, the demand for water is on the rise which can be compared from the growth rate of some selected wards of the city where depletion was noticed to be on the rise but there still remains few places in the city where the depletion curve more or less remains constant. The rate of depletion with respect to increase in population is evident in western section and southern section of city.