Integrating Gravimetry Data With Thermal Infra‐Red Data From Satellites to Improve Efficiency of Operational Irrigation Advisory in South Asia

Abstract

Groundwater, one of the most important freshwater resources, satisfies significant water demand required by irrigational (42%), domestic (36%), and industrial uses (23%) (Döll et al., 2012;Famiglietti, 2014;Taylor et al., 2013). It also sustains rivers during dry seasons, by providing base flow. However, a growing population requires increased agricultural productivity. This consequently triggers a significant and often unsustainable extraction of groundwater around the world (Siebert et al., 2015). The evident correlation of groundwater depletion with extensive irrigation activity is very distinct in South Asian countries, where the monsoon weather system dominates the precipitation regime. The monsoon is a system with prevailing winds along a certain direction. It brings in bountiful amounts of rain (wet phase) followed by a reversal in wind direction resulting in no precipitation (dry phase) (Ramage, 1971). Each phase lasts at least 4-5 months and the dry phase is markedly nonprecipitating with low streamflow and dry soils. During the dry phase of the monsoon, irrigation activities for food production can be sustained only from groundwater recharged by the rains from previous wet phase.South, Southeast, and East Asia sustain extensive irrigation systems by relying mostly on groundwater pumped during the dry season, which is (hereafter) the period spanning from November to April (Hossain et al., 2017). Hence, the water and food security in South Asia is deeply rooted in groundwater resources of the transboundary aquifer system of Indus-Ganges-Brahmaputra-Meghna (IGBM) rivers that supports a net cropping area of 1.14 million km 2 (Malakar et al., 2020;Mukherjee et al., 2015). For South and East Asia, the total annual water withdrawal is roughly 1,981 km 3 , which is about 50% of world total (FAO, 2016a(FAO, , 2016b(FAO, , 2016c. Agriculture requires around 82% of the total freshwater withdrawal in Asia, which is much higher than global agricultural water withdrawal (70%) (FAO, 2016a(FAO, , 2016b(FAO, , 2016c. The highest water withdrawal in South Asia is reported in India comprising of about 10,400 m 3 /ha (1,040,000 m 3 /km 2