Impact of Concepts and Spatial Scales on Irrigation Efficiency for Sustainable Water Resources Management: A Review

Abstract

This paper provides a review of different ‘irrigation efficiency’ concepts evolved over the time since the term was originally conceived, from an engineering perspective; the impact of scale, i.e., from field to basin, on savings in water demands through hightech irrigation—the efficiency paradox; the role of rice cultivation—water guzzler or recharge basin; and policies for transforming high-tech irrigation into water-conserving interventions. As these issues are interlinked, their synergetic resolution is necessary for establishing sustainable irrigated-agriculture at basin scale. There is a consensus on the utility of classical irrigation for designing the capacity of different components of an irrigation system; and also appreciation of the fact that it does not represent the true picture of water savings/losses at the basin scale. Consumed fraction-based water accounting makes a better representation of irrigation performance from field to basin scales. In literature, studies from different countries revealed the positive impact of hightech irrigation in improving land productivity and income at the field scale but without any significant water conservation for further use to other sectors/locations. Many studies also indicate that introduction of high-tech irrigation in water-scarce but abundant irrigable land regions led to increased water use, which resulted in further decline of water table and/or deterioration of groundwater quality. The increase in water demand on improving irrigation efficiency is known as the efficiency paradox or rebound effect. In water-scarce areas, high-tech irrigation should be promoted with caps on water withdrawals even if the water transfer to downstream areas or other uses is not required. High-tech irrigation is helpful in reducing transaction costs for achieving water conservation, but gold plating of irrigation infrastructure alone would not be sufficient. This study emphasizes on enactment and enforcement of policies for regulating total water withdrawal, limiting irrigated area, and adopting ecologically-compliant cropping patterns for establishing sustainable irrigated-agriculture without the rebound effect.