Anthropogenic and Climate Contributions on the Changes in Terrestrial Water Storage in India

Abstract

Despite the rapid depletion of groundwater and significant changes in surface water storage, the role of anthropogenic and climatic factors on terrestrial water storage (TWS) in India remains largely unexplored. Here, we provide a hydrologic framework based on the Variable Infiltration Capacity-SIMple Groundwater Model (VIC-SIMGM) and Gravity Recovery and Climate Experiment (GRACE) data sets to estimate the contribution of climate variability and anthropogenic groundwater pumping on TWS in the Indian basins. The VIC-SIMGM model was satisfactorily calibrated and evaluated against observed monthly streamflow and groundwater anomalies for the 17 river basins in India. The modeling setup combined with the GRACE data can be used for understanding the role of climate variability on surface and groundwater (shallow) storage in India. A significantly high correlation between TWS anomaly from GRACE (TWSA GRACE ) and the VIC-SIMGM (TWSA VIC ) was found in the majority of India except in northwest India. The negative correlation in northwest India is primarily due to considerable groundwater pumping for irrigation. Groundwater storage anomaly explains a significant variability of GRACE TWSA in India, indicating the influence of anthropogenic groundwater pumping for irrigation. However, in the absence of anthropogenic influence, soil moisture is the major contributor to TWSA in the majority of India. The net anthropogenic depletion of TWS in north India is considerably higher than that estimated from the GRACE as the increase in precipitation has, during the recent decades, contributed to slowing down the declining rate of TWS.

Propagation of Meteorological to Hydrological Droughts in India

“…These catchment characteristics, which are incorporated in BFI, control drought propagation, speed, and recovery (Hellwig et al, 2020; Hellwig & Stahl, 2018; Yang et al, 2017). For instance, the Godavari basin experienced an increasing trend of terrestrial water storage (Asoka & Mishra, 2020). The high base flow during the drought years in the Godavari basin could help drought to propagate at a slower rate, which ultimately reflected in high propagation time.…”

Strong Influence of Changes in Terrestrial Water Storage on Flood Potential in India

“…We estimated groundwater storage anomalies from the GRACE‐TWSA using the VIC simulated soil moisture (see Asoka & Mishra, 2020; Asoka et al., 2017 for more details). The relative contribution of groundwater and precipitation on GRACE‐TWS was calculated for the 2002–2016 period (Figure 8).…”

“…The relative contribution of groundwater is significantly higher than precipitation on TWS for all the river basins (Figure 8). For instance, the relative contribution of groundwater on TWS in Ganga, Brahmaputra, and South Coast river basins is higher than 0.6, which can be attributed to the high persistence of groundwater (Asoka & Mishra, 2020; Asoka et al., 2017). Sabarmati, Mahi, and Northeast coast basins showed the lowest relative contribution of groundwater on TWS.…”

“…More information on the estimation of groundwater anomalies can be found in Asoka et al. (2017, 2018) and Asoka and Mishra (2020).…”

“…Apart from the pumping for irrigation and monsoon precipitation characteristics, policy measures taken by the state governments to reduce groundwater pumping and for enhancing groundwater recharge can also affect groundwater storage variability (Meghwal et al., 2019). Nonetheless, persistent groundwater depletion has posed enormous water stress and resulted in severe groundwater droughts in the Indo‐Gangetic plain and Northwest India (Asoka et al., 2017; Asoka & Mishra, 2020; Gleeson et al., 2012; Rodell et al., 2009; Tiwari et al., 2009). While the role of groundwater has been widely examined for drought assessment (Castle et al., 2014; Kumar et al., 2016; Loon et al., 2017; Shah & Mishra, 2020a, 2020b; Thomas et al., 2017), its impacts on flood potential (Reager & Famiglietti, 2009) in India remain unexplored.…”