ABSTRACT
South Asian countries, comprising India, Pakistan, Nepal, and Bangladesh and having a total geographical area of only 401.72 million hectares (m ha), hold nearly half the world’s population of 3.1 billion (FAO 1999). Nearly half of the land area in South Asia is devoted to agriculture, which provides livelihood and food security for 59% of the world’s population. For agricultural production in South Asia (SA), irrigation is the most crucial input because about 40% of cropland is irrigated agriculture that accounts for 60%–80% of food production (Yadvinder-Singh et al. 2014). Agricultural water use is estimated to consume almost 95% of the withdrawn water in South Asian countries, which is well above the global average of 70% (Babel and Wahid 2008). Groundwater in the northwestern Indo-Gangetic plains (IGP) is being depleted at 13 to 17 km3 yr-1 (Rodell et al. 2009), which is a major concern for the current growth rate and sustainability of South Asian agriculture (Hira 2009). Negative environmental effects related to irrigation are increasing as overexploitation of groundwater and poor water management lead to the steady rate of decline in the depth to the groundwater in much of the rice-wheat (RW) areas of northwestern India and parts of Pakistan (Qureshi et al. 2003; Ambast et al. 2006; Hira 2009; Rodell et al. 2009). The number of tube wells in Indian Punjab, for example, has increased from 0.30 million in 1975 to 1.232 million in 2007 (Anonymous 2007), which led to a groundwater table decline from 18 m to 27 m from 20002009. Similarly, in Pakistan, both groundwater and surface water resources are decreasing due to overexploitation of water resources and the adverse impact of climate change on water resources (Gill 2001).
