Irrigation efficiency and water-policy implications for river basin resilience

Abstract

Abstract. 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 hydrological variability, increasing freshwater demand for other uses including ecosystem water needs, and low economic productivity of irrigation compared to most other uses. We identify three classes of unintended consequences, presented here as paradoxes. Ever-tighter cycling of water has been shown to increase resource use, an example of the efficiency paradox. In the absence of effective policy to constrain irrigatedarea 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, southwestern 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.

The water–food–energy nexus in Pakistan: a biophysical and socio-economic challenge

“…But, as discussed above, net efficiencies may be much lower than anticipated (Ahmad et al, 2014;Scott et al, 2014). Other, local, solutions may be politically more achievable: small-scale hydropower at head works; improved irrigation efficiency in well-identified places; improved water delivery; and managed aquifer storage to keep groundwater tables higher and reduce energy use in pumping.…”

“…Ahmad et al (2014) found savings from efficiency measures at the farm-scale did not translate to savings at the basinscale. One reason for this is because of system "rebound": local efficiency gains are consumed in other ways, leading to no system-scale saving (Scott et al, 2014). For example, increased efficiency enables farmers to increase land area under production for the same water use.…”

Moving sociohydrology forward: a synthesis across studies

“…Comparative studies can be primarily qualitative, investigating a limited number of sites in great detail, with the goal of generating conceptual understanding. In this mode, Scott et al (2014) compared three agricultural catchments to understand the relationship between irrigation efficiency improvements and basin resilience. Across three cases, they find that expanding irrigation efficiency without limits on use or irrigated area may increase production, but it could worsen resilience to water scarcity.…”

Evolving conceptions of the role of large dams in social-ecological resilience

“…River basins are SES, or "social-hydrological systems," providing water for both human needs and ecosystem functions, which are inherently linked (Scott et al 2014). Rivers around the world have been influenced by human infrastructure including dams, weirs, barrages, diversions, tunnels, aqueducts, bridges, etc., that lead to shifts in the natural flow regime (Poff et al 1997) and loss of biodiversity and ecosystem services.…”

“…In the context of whitewater recreation, cultural ecosystem services such as increasing human use as seen on the White Salmon River in Washington State is perceived to be threatening the recovery of the river as it continues to rewild postdam removal (Gimblett et al 2017). Failing to holistically address threats to a river and ensuing impacts on ecosystem services may decrease the resilience of the entire SES (Scott et al 2014). …”