Irrigation efficiency and water-policy implications for river-basin resilience

Abstract

Rising demand for food, fiber, and biofuels drives expanding irrigation withdrawals from surface- 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 <i>efficiency paradox</i>. 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 <i>scale paradox</i>) 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 <i>sectoral paradox</i>. This paper briefly examines policy frameworks in 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

Progress in socio‐hydrology: a meta‐analysis of challenges and opportunities

“…37 Introduction of water saving technologies such as drip irrigation may cause increased dryland salinity, 31 and contribute to the so-called efficiency paradox of yet more land being irrigated instead of water being left to the environment, or the 'scale paradox' of reduced return flows downstream. 35 It therefore remains unclear as to what extent technology can ensure a sustainable future. A conservative observation is that technology-driven economic growth leads to increased environmental hazard and degradation such as higher flood risk, reduced return flow downstream, and increased salinity in coastal areas.…”

“…34 Rigid water governance may lead to another set of unintended consequences when new technologies are introduced. Agricultural water that is 'saved' through irrigation efficiency improvements may end up being used in other sectors such as industrial and municipal water use, 35 wiping out the gains of using such technology. Water saving through smart irrigation technology such as drip irrigation may give an impression of abundance of water to farmers, often leading to adoption of water intensive crops or diversion of saved water to industrial or domestic use.…”

“…Scott et al 35 addressed the impacts of increased efficiency in water use and water savings on the resilience of socio-hydrological systems by studying three contemporary river basins. They showed that water 'saved' through irrigation technology improvements may lead to unintended consequences for water use at multiple scales and in multiple sectors.…”

“…Examples include dams, 71 irrigation technology (sprinkler irrigation, drip irrigation etc. ), and irrigation structures, 31,35,53,54,63 groundwater pumping, 60 levees against flooding, 37,61,62 plant breeding, 31 etc. It sustains wealth generation even under increasing population pressure and in this way helps to sustain positive population growth in spite of finite resources.…”

Cation exchange in a temporally fluctuating thin freshwater lens on top of saline groundwater

“…The consequences of an increasing sea level and climate change for salinization of coastal zones has been investigated over the past years by Giambastiani et al (2013), Langevin and Zygnerski (2013), Colombani et al (2014) and Feseker (2007) and De Louw et al (2011Louw et al ( , 2013 for deltas in Italy, Florida (USA), Argentina, Germany and The Netherlands respectively. Scott et al (2014) investigated the development of shallow brackish water in Bangladesh. Lenses, formed by infiltrating rainwater 'floating' on saline groundwater, are often a major source of freshwater.…”