A comprehensive study to understand the relationship of urbanization and population density with GRACE ΔTWS for selected study regions in India during 2003-2017

9 For the time period of January'2003 to January'2017, this pan-India study investigates the 10 relationship of urbanization and population density with Ground Water Storage (GWS) 11 indicated by Gravity Recovery and Climate Experiment (GRACE) derived terrestrial water 12 storage changes ( TWS). Analysis of GRACE TWS across India reveals the evidence of 13 signi cant declining trend ( 0:912 0:455 cm/year) of the same in northern part of India 14 encompassing Ganga-Brahmaputra river basin and North-West India during this time. 15 Interestingly, for the same time period (2002-Quarter1 To 2016-Quarter4), this particular 16 belt with declining TWS, has observed signi cant positive trend in precipitation (17:89 17 11:32 mm/year) and no signi cant trend for temperature. In addition, for the mentioned 18 time period, we've observed higher growth rate in agricultural electricity consumption 19 (80:60% Growth with CAGR of 7:67%) in this region compared to the same for the 20 rest of India (72:30% Growth with CAGR of 7:04%). We believe that the increasing 21 uncertainty in precipitation as indicated by the rising trend of it's temporal variability, 22 could have led to higher dependence on groundwater withdrawal in agricultural sector, 23 measured indirectly using agricultural electricity consumption data. Also, signi cant 24 negative correlation ( = 0:3128 & p-Value < 0:05) between changes in TWS and 25 associated changes in population density has been found for this region during the same 26 ∗Corresponding author, amritendum@iisc.ac. in 1 period of 2003-17. These observations strongly suggest that the depletion of TWS in this 27 region could be primarily attributed to anthropogenic activities rather than to changes in 28 meteorological variables. As urbanization drives population density, in order to understand 29 the relationship of the same with TWS, panel data regression analysis has been conducted 30 for 9 selected study sites of 1 spatial resolution across di erent geographic locations in 31 India during 2003-2017. Population density, precipitation and temperature along with 32 urbanization, have been used as explanatory variables in the panel data regression for 33 understanding the variations in GRACE TWS. Results suggest that precipitation & 34 urbanization exhibit signi cant positive ( = 14:1535 & p-Value = 3:018e ) & negative 35 ( = 11:5961 & p-Value = 8:394e ) slopes respectively with TWS and together 36 they could explain 66:93% of variability of the same. Similarly, it has been observed 37 that interaction e ect of urbanization & population density exhibit a signi cant negative 38 association ( = 0:0053 & p-Value = 5:127e ) with GRACE TWS and 77:76% of 39 variation in TWS could be explained with the help of the same along with precipitation 40 which demonstrates signi cant positive slope ( = 14:7984 & p-Value = 6:009e ) w.r. t 41 TWS. Thus, increase in anthropogenic indicators like urbanization & population density, 42 indicates decrease in GRACE TWS re ecting depletion in GWS. 43