Regional blending of fresh and saline irrigation water: Is it efficient?

Abstract

[1] Blending fresh and saline irrigation waters is implemented in many countries facing water scarcity. However, when analyzed at the field level, previous economic studies have indicated that blending fresh and saline water is suboptimal. This paper examines the blending issue on a regional scale, where both water sources and land are concurrently allocated to crops. Regional water distribution networks that enable salinity adjustment at the field level are compared to networks that allow controlling water salinity on a regional scale only, such that salt concentrations cannot differ by crop. We characterize the conditions for blending to be an optimal strategy under regional salinity control networks, and show that these conditions can be met by an empirical water production model commonly used in the literature. Empirical analysis of 16 regions in Israel revealed optimal blending in six of them. However, regardless of whether blending is optimal or not, the optimal fresh-water application is higher under regional salinity control networks, implying that blending does not support freshwater conservation. The paper analyzes the relationship between water and land constraints' shadow values, and the properties of the two water distribution networks. We show that although farming revenues are higher under networks that allow assignment of specific water salinities to crops, regional salinity control networks can become more profitable to farmers who face prices set endogenously so as to be the binding factor on the use of constrained water and land. The implications of the network selection on intraregional water supply costs are discussed.Citation: Kan, I., and M. Rapaport-Rom (2012), Regional blending of fresh and saline irrigation water: Is it efficient? Water Resour.

Poor quality water utilization for agricultural production: An environmental perspective

“…The interrelations between field and regional level irrigation management for the case of Israel were examined by Kan and Rapaport-Rom (2012). The study provided the guidelines for planners regarding the blending of fresh and poor quality water for irrigation.…”

Large‐Scale Desalination and the External Impact on Irrigation‐Water Salinity: Economic Analysis for the Case of Israel

“…Water Resources Research VALUE is a positive mathematical programming (PMP) partial-equilibrium model of Israel's agriculture used to analyze rural landscape amenities (Kan et al, 2009), organic-waste policies (Kan et al, 2010;Raviv et al, 2017), climate change (Palatnik et al, 2011;Zelingher et al, 2019), and water management (Baum et al, 2016;Kan & Rapaport-Rom, 2012). The decision variables in VALUE are the cultivated lands allocated to the 55 crops in each of the 18 nodes specified in MYWAS as agricultural water-consumption regions.…”

Economic Impacts of Climate Change on Vegetative Agriculture Markets in Israel

“…1 The effect of precipitation was already included in previous versions of the VALUE model (Kan and Rapaport-Rom 2012). For the present application, we updated precipitation forecasts for the periods under consideration.…”

“…where e jit (ft/year) is the evapotranspiration, expressed as a function of water application W jit = w 1 jit + w 2 jit + w r jit , and water salinity S jit = ∑ s sa w sa jit , where s 1 = 1 (dS/m), s 2 = 2 (dS/m), and s r = 0.1 (dS/m); the indexes for the water application and salinity parameters refer to, respectively, freshwater irrigation (w 1 jit , s 1 ) , non-freshwater irrigation (w 2 jit , s 2 ) and precipitations during crop-i's growing season (w r jit , s r ) ; ē ji , and 1 ji through 5 ji are parameters adopted from Kan and Rapaport-Rom (2012).…”