Amritendu Mukherjee , Parthasarathy Ramachandran

This work investigates the relationship between urbanization, population density and meteorological variables (temperature & precipitation) on groundwater storage in India during the period January'2003 to January'2017. Variations in groundwater storage have been analysed using Gravity Recovery and Climate Experiment (GRACE) derived variations of Terrestrial Water Storage (TWS). In the first part of this work, we have studied changes in TWS across India from January'2003 to January'2017 and have found evidence of its significant declining trend (-0.912 +/-0.455 cm/year) in the northern part of India encompassing Ganga-Brahmaputra river basin and North-West India. As TWS serves as a strong indicator for groundwater storage, its declining trend implies significant depletion of groundwater in this belt during this period. Interestingly, for the same time period, this particular belt with declining TWS has observed a significant positive trend in precipitation and no significant trend for temperature. Also, we have observed higher growth rate in agricultural electricity consumption and population density in this region compared to the rest of India. These observations strongly suggest that the depletion of TWS in this area could primarily be attributed to anthropogenic activities rather than to changes in meteorological variables. Motivated by these observations, we've investigated further the relationship between TWS & urbanization which increases population density. Panel data regression analysis was conducted for 9 selected study sites across different geographic locations in India for the period 2003-2017. Index based classification algorithms (PB1BI & BRSSI) have been applied jointly to compute the percentage of urbanization from Landsat7 imagery. Population density, precipitation and temperature along with urbanization, have been used as explanatory variables in the panel data regression for understanding the variations in TWS. Results suggest that precipitation & urbanization exhibit significant positive & negative effects respectively with TWS and together they could explain 66.93% of the variability in the data. Similarly, it has been observed that interaction effect of urbanization & population density exhibit a significant negative association with GRACE TWS and 77.76% of the variation in TWS could be explained with the help of the same along with precipitation. This indicates the significant effect of an increase in anthropogenic indicators like urbanization & population density on the depletion of groundwater storage.