Groundwater Variability Across India, Under Contrasting Human and Natural Conditions. Issue 4 (2nd April 2022) - Panda, Dileep K.
Abstract: Characterizing local to regional scale water cycles and water resources will be crucial for achieving the United Nations' water‐related Sustainable Developmental Goals. However, quantification and understanding of groundwater extraction across scales have been hampered by inadequate water usage reporting and limited information on irrigation practices. Here we analyze observations from ∼15, 000 groundwater monitoring wells and the Gravity Recovery and Climate Experiment satellites together with irrigation, agricultural, and meteorological datasets to show how drought‐induced coupling between natural and anthropogenic groundwater storage variations has caused sustainability challenges in India, the world's biggest consumer of groundwater for irrigation. Notably, the mechanisms and consequences of such coupling differ significantly depending on aquifer types. In Andhra Pradesh's hard rock aquifer, groundwater declines have been limited, despite the nearly constant water scarcity that its farmers face. Moreover, its free farm power policy involves an annual irrigation energy consumption of 26 billion kWh that costs US$ 2.5 billion, possibly unparalleled compared to any other part of the world of similar size (0.27 million km 2 ). In West Bengal's highly permeable alluvial aquifer, the water table is declining rapidly (15 cm/yr) due to a policy that encourages irrigation. Situated between these two states, Odisha's aquifer shows substantial resilience to drought, owing to the state's relatively natural landscape and forest restoration policy. The findings of this study provide new insights to understand the divergent aspects of groundwater irrigation in north versus south India, which can enable development of adaptation and mitigation strategies to avert the looming water crisis. Plain Language Summary: Groundwater is a vital resource in regions where rainfall is inconsistent or surface waters are inadequate to meet agricultural, industrial, and municipal/domestic needs. In many parts of the world, groundwater levels are declining due to massive withdrawals to support irrigated agriculture. The problem is compounded when drought strikes and policies do not incentivize water conservation. Such has been the case in India. In fact, India is the world's biggest consumer of groundwater for irrigation. However, India is not uniformly afflicted by groundwater depletion, and this study aims to understand why. We find that groundwater variability and the interactions between human and natural conditions are largely controlled by the aquifer type. In fact, farmers in south India are more prone to climate variability on an interannual scale, relying on rainfall every year to replenish the thin hard rock aquifer. In turn, farmers in north India extract the currently reliable but not sustainable static groundwater stored in the thick alluvial aquifers. This difference necessitates distinctive groundwater management plans to ensure resilient agriculture, deemed the economic backbone of the country. Key Points: Characterized the hydrological and socioeconomic divergence associated with groundwater irrigation in India North India's most productive aquifer experiences severe groundwater depletion under changing climate and policy interventions South India's water demands and policies could engender a socioeconomic crisis, whereas natural ecosystems exhibit exemplary resilience