Kaushal K. Garg

Opportunities to Build Groundwater Resilience in the Semi‐Arid Tropics

Agricultural water management (AWM) is the adaptation strategy for increasing agricultural production through enhancing water resources availability while maintaining ecosystem services. This study characterizes groundwater hydrology in the Kothapally agricultural watershed, in hard rock Deccan plateau area in India and assesses the impact of AWM interventions on groundwater recharge using a calibrated and validated hydrological model, SWAT, in combination with observed water table data in 62 geo-referenced open wells. Kothapally receives, on average, 750 mm rainfall (nearly 90% of annual rainfall) during the monsoon season (June to October). Water balance showed that 72% of total rainfall was converted as evapotranspiration (ET), 16% was stored in aquifer, and 8% exported as runoff from the watershed boundary with AWM interventions. Nearly 60% of the runoff harvested by AWM interventions recharged shallow aquifers and rest of the 40% increased ET. Water harvesting structures (WHS) contributed 2.5 m additional head in open wells, whereas hydraulic head under natural condition was 3.5 m, resulting in total 6 m rise in water table during the monsoon. At the field scale, WHSs recharged open wells at a 200 to 400 m spatial scale.

Improving water use in tropical rain-fed systems: the situation in India

Providing global food security for an ever-growing population, predicted to reach nine billion by 2050, and reducing poverty are challenging tasks. Growing per capita income in the emerging giant economies such as Brazil, Russia, India, China and South Africa (BRICS) means increased pressure on global food production due to changing food habits. This increased food production has to be met using finite water and land resources. The quantity of available water and land has not increased since 1950, but the availability of water and land per capita has declined significantly due to an increased global human population. For example, in India, per capita water availability has decreased from 5177 m3 in 1951 to 1625 m3 in 2011 due to the population increasing from 361 million in 1951 to 1.15 billion in 2011, which is expected to rise to 1.39 billion by 2025 and 1.64 billion by 2050, with an associated decrease in per capita water availability of 1345 m3 in 2025 and 1140 m3 by 2050 (Wani et al., 2012). The distribution of water and land resources varies in different countries and regions of the world, and the current population is expected to increase rapidly. In this chapter, we analyse the current status of agricultural water use in tropical rain-fed areas, assess the potential and propose a new paradigm to manage agricultural water efficiently by adopting various land, water, nutrient and crop management technologies.