Irrigation efficiency and water-policy implications for river basin resilience
Autores"Scott, C. A. Vicuña, S. Blanco-Gutiérrez, I. Meza, F. Varela-Ortega, C."
Instituição do autor correspondenteUniversity of Arizona, School of Geography & Development, and Udall Center for Studies in Public Policy
Revista e nºHydrology and Earth System Sciences 18: 1339-1348
Inter-American Institute for Global Change Research (project SGP-CRA #005, supported by the National Science Foundation, NSF grant no. GEO-1138881), by NSF grant nos. DEB-1010495, FONDECYT grant no. 1110297, as well as European Commission Project MEDIATION, FP7, no. 244012
Rising demand for food, fiber, and biofuels drives expanding irrigation withdrawals from surface water and groundwater. Irrigation efficiency and water savings have become watchwords in response to climate-induced hydrolog ical variability, increasing freshwater demand for other uses including ecosystem water needs, and low economic produc- tivity of irrigation compared to most other uses. We identify three classes of unintended consequences, presented here as paradoxes. Evertighter cycling of water has been shown to increase resource use, an example of the efficiency paradox. In the absence of effective policy to constrain irrigated- area expansion using “saved water”, efficiency can aggravate scarcity, deteriorate resource quality, and impair river basin resilience through loss of flexibility and redundancy. Water scarcity and salinity effects in the lower reaches of basins (symptomatic of the scale paradox) may partly be offset over the short-term through groundwater pumping or increasing surface water storage capacity. However, declining ecological flows and increasing salinity have important implications for riparian and estuarine ecosystems and for non-irrigation human uses of water including urban supply and energy generation, examples of the sectoral paradox. This paper briefly considers three regional contexts with broadly similar climatic and water-resource conditions – central Chile, south-western US, and south-central Spain – where irrigation efficiency directly influences basin resilience. The comparison leads to more generic insights on water policy in relation to irrigation efficiency and emerging or overdue needs for environmental protection.