Technical concepts related to conservation of irrigation and rainwater in agricultural systems

Abstract

Forty percent of freshwater withdrawals in the United States are for irrigated agriculture, which contribute more than $50 billion to the economy. Increasing diversions of water for urban, environmental, and other uses will likely decrease water available to agriculture. Water conservation in agriculture is touted as a good method for minimizing the impact of reduced agricultural diversions on production. Because “wasted” water is often reused until it reaches the ocean, there are limitations to the true water savings that result from programs that aim to increase irrigation efficiency. True water savings can come from four areas: reduction of unnecessary evaporation and transpiration, more effective use of rainfall, reduction of deep percolation water that becomes severely degraded in quality, and reduction of runoff from fields that is not reusable downstream. Any other reduction in net water consumption must come from reductions in evapotranspiration from the crops grown, which requires either reduction in acreage or reduction in crop yield brought on by intentional plant water stress. Other benefits of field or district‐level water conservation may include increased in‐stream flows (due to lower diversions) and energy conservation due to less pumping or more hydroelectric production, but not result in true water savings, since unconsumed water returns as a usable water resource. Understanding the hydrologic settings is critical to determining true water savings from conservation practices. On‐farm water conservation practices that provide true water savings at one location may be ineffective at another. In large irrigation projects, water delivery limitations often present obstacles to on‐farm water conservation efforts.

Passing the Panda Standard: A TAD Off the Mark?

“…This may be significant, because intensive fish production systems reliant on commercial fish feeds produced by using primary outputs of terrestrial agricultural production are potentially more water consumptive in this regard than semi-intensive alternatives, because more than 1 m 3 of water is required to produce a single kilogram of grain (Pimental et al 2004). Furthermore, the effects of pond construction are misconstrued because, although subject to losses through evaporation and seepage, ponds tend to be net contributors to overall water budgets since they serve to harvest and store rainwater which would otherwise be lost as run-off (Clemmens et al 2008).…”

Achieving Water and Food Security in 2050: Outlook, Policies, and Investments

“…The water required to support additional transpiration in 2050 can come from several sources, including new development of surface water and groundwater resources for use in agriculture, and better efforts to capture and re-apply surface runoff and utilize shallow groundwater directly in crop production [49][50][51]. Farmers also can reduce evaporation and improve distribution uniformity by replacing surface irrigation methods with drip systems and micro-sprinklers, where feasible [52], and they can minimize transpiration by non-beneficial plants by removing vegetation from irrigation canals.…”

Review.Water resources deficit and water engineering

“…Finally, in the controversy on the effects of improving and modernizing of irrigable areas for water conservation, it is necessary to emphasize that there is an agreement on the environmental improvements derived from the improvement of irrigation infrastructures (Ortega et al, 2002;Causapé et al, 2004Causapé et al, , 2006Clemmens et al, 2008;Lecina et al, 2009), particularly when these actions are linked to overall improvements in the water use area (including management, irrigation scheduling, availability of irrigation advisory services, among others) .…”