Use of GRACE time-series data for estimating groundwater storage at small scale
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Ó Indian Academy of Sciences (0123456789().,-volV)(0123456789( ).,-volV)
Use of GRACE time-series data for estimating groundwater storage at small scale CH SAMUREMBI CHANU1, HARIKA MUNAGAPATI2,* , V M TIWARI2, ARVIND KUMAR3 and L ELANGO1 1
Department of Geology, Anna University, Chennai, Tamil Nadu, India. Geophysical Research Institute, CSIR, Hyderabad, India. International Co-operation Division, Department of Science and Technology, New Delhi, India. *Corresponding author. e-mail: [email protected] 2 National 3
MS received 6 December 2019; revised 24 June 2020; accepted 25 June 2020
This study integrates the time series of satellite data, i.e. (terrestrial water storage (TWS) extracted from Gravity Recovery and Climate Experiment (GRACE), soil moisture (SM) from Global Land Data Assimilation System (GLDAS), rainfall from Tropical Rainfall Measuring Mission (TRMM)) with in-situ data, i.e. (groundwater (GW) observatory well data and surface water (SW) as reservoir level from Tamil Nadu Public Work Department (TN PWD)) to estimate the water storage of the study area for the period from 2002 March to 2016 December. The study area encompasses three districts of Tamil Nadu State – Chennai, Kancheepuram and Tiruvallur. It was previously observed that the groundwater level in this study area is decreasing at an alarming rate. Trends and residuals of the times series of all the previously stated components were analyzed. Negative trends were observed in the case of DSW, DSM, DGW, DTWS-GRACE, but rainfall shows a slight positive trend. Rainfall, being the input for water storage, a marginal increase in rainfall cannot aAect the variability of DSM, DSW, DGW and DTWS-GRACE. DTWS decreases approximately 0.12 cm yr1 averaged water level equal to a total volume 7.5 km3. The result of this study shows a decrease in the total storage of groundwater in the study area during the study period from 2002 March to 2016 December. Seawater intrusion due to an increase in sea surface height also shows an impact on DTWS derived from grace, in the form of anomalously elevated DTWS. A good agreement between DTWS-GRACE and DTWS-in-situ is found except where sea-water intrusion occurs. Keywords. GRACE; terrestrial water storage; groundwater; rainfall; soil moisture.
1. Introduction Globally, half of the domestic water demands is contributed by groundwater and is the main source for industrial, agriculture and irrigation water demand (Ouma et al. 2015; Xiao et al. 2015). In some regions, a rapid decline in water table is caused by over exploitation of groundwater resources which leads to faster depletion of water storage, compared to the natural restoration
capacity (Tiwari et al. 2011). A thorough understanding of the hydrological cycle is essential to monitor the total water storage on the surface and sub-surface and for water management for the continually increasing population (Green et al. 2011; Dapeng et al. 2014; Bonsor et al. 2018). The impact of population explosion on the management of groundwater has been well recognised
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