Climate Change and Water Supplies: Options for Sustaining Tank Irrigation Potential in India

Abstract

K Palanisami ([e-mail]) is with the International Water Management Institute, ICRISAT; Ruth Meinzen-Dick is with the International Food Policy Research Institute, Washington; and Mark Giordano is with the International Water Management Institute, Colombo. Climate change will affect water supplies in south Asia, where high-intensity floods and droughts are expected in the future. Increasing water storage is a key adaptation strategy, and the experience of irrigation tanks illustrates both the potential and challenges of this adaptation response. Although there are over 2,08,000 tanks in India, irrigating about 2.3 million hectares in 2000-01, the net area irrigated by tanks declined by 29% between 1990-91 and 2000-01 and by 32% between 2001 and 2008. This paper reviews the challenges faced by tank irrigation and examines options for improving their performance – revenue mobilisation through multiple use of tanks, augmenting groundwater resources in the tanks, integrating social forestry and desilting, and tank modernisation. The Fourth Assessment report of the Inter-Governmental Panel on Climate Change (IPCC 2007a) has confirmed the increasingly strong evidence for the influence of human activity on the global climate. The IPCC has projected that average global temperature of the air above the earth’s surface would rise by 1.1°C-6.4oC over the next 100 years depending upon the scenario. Although there is considerable uncertainty in the precipitation projections for the future, it is likely that precipitation may increase in high latitudes and parts of tropics and decrease in some sub-tropical and lower mid-latitude regions. More floods, droughts, decreases in agricultural and aquaculture producti vity, displacement of millions of coastal dwellers due to sea level rise and intense tropical cyclones, and the degradation of mangroves and coral reef ecosystems are considered to be some of the likely consequences of climate change (IPCC 2007c). Indeed, heavy precipitation related floods, storm surges, and relatively higher temperatures have led to devastating consequences in recent years. For south Asia (Indian region), the IPCC has projected a rise in temperature of 0.5oC-1.2oC by 2020, 0.88oC-3.16oC by 2050 and 1.56oC-5.44oC, depending on the scenario of future development (IPCC 2007b). Overall, the temperature increases are likely to be much higher in the winter (rabi) season than in the rainy season (kharif). Precipitation is likely to increase in all time slices in all months, except during December-February when it is likely to decrease. Such global climatic changes will affect agriculture through their direct and indirect effects on crops, soils, livestock and pests.