Recent agroeconomic studies in water‐scarce countries such as Spain, Australia, Saudi Arabia, and Israel have revealed the economic viability of irrigating high‐value crops with desalinated water. However, the worldwide growth of large‐scale desalination capacities is primarily designed to resolve urban‐water scarcity, disregarding the impact of desalination on irrigation‐water salinity. We develop a dynamic hydroeconomic programming model where infrastructure capacities and allocations of water quantities and salinities in a regional water distribution network are endogenous. We show that subsidizing desalination is socially warranted because the associated reduction in irrigation‐water salinity is an external effect of water consumption by all water users. Empirical application to the entire state of Israel indicates that large‐scale desalination of seawater and treated wastewater for irrigation is optimal. This result stems from the large share of irrigation‐intensive salinity‐sensitive high‐value crops, motivated by Israel's policies to support local agriculture. Ignoring salinity results in a 45% reduction in desalinated irrigation water, a 29% reduction in farming profits, a 250% increase in water suppliers' profits, and an average deadweight loss of $1,200 a year per hectare of arable land.

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大规模海水淡化及其对灌溉水盐度的外部影响：以以色列为例的经济分析

最近在缺水国家（如西班牙，澳大利亚，沙特阿拉伯和以色列）进行的农业经济研究表明，用淡化水灌溉高价值作物具有经济可行性。但是，全球范围内的大型海水淡化能力的增长主要是为了解决城市缺水问题，而忽略了海水淡化对灌溉水盐度的影响。我们开发了动态的水力经济计划模型，该模型的基础设施能力以及区域配水网络中的水量和盐分分配是内生的。我们表明，对海水淡化进行补贴在社会上是有保证的，因为与之相关的灌溉水盐度降低是所有用水户用水的外部影响。对以色列整个州的经验应用表明，大规模海水淡化和灌溉灌溉废水是最佳的。造成这种结果的原因是，在以色列支持当地农业的政策的激励下，对灌溉密集的盐分敏感的高价值作物的份额很大。忽略盐分会导致淡化灌溉水减少45％，农业利润减少29％，供水商利润增加250％，每公顷耕地每年平均失重损失1200美元。