Abstract Climate change has drastic impacts on water resources and agricultural productivity, especially in arid and semi-arid environments. The present study simulated and explored the economic impacts of climate change on the water and agriculture sectors of the Zayandehroud river basin in Iran for the years 2040 and 2070in three major phases. In phase I, two general circulation models (GCM) (HadCM2 and CGCM3T63), an artificial neural network (ANN) rainfall-runoff model, and crop-water production functions were applied to evaluate the biophysical impacts of climate change on water resources and various crop yields. In Phase II, the aforementioned models were integrated into the hydro-economic spatial equilibrium model of Zayandehroud basin (HE-SEMZ), and the effects of the modeled runoff and socio-economics changes on the economic welfare of the water sector, its distributional consequences, and on temporal-spatial water prices and allocation were simulated. In Phase III, the simulated optimal allocated water to the agriculture sector was introduced into a positive mathematical programming (PMP) model of the agriculture sector to simulate follow-on changes in crop acreage, cropping patterns, and farmers’ gross benefit. In this modeling framework, the role of two no-cost adaptation strategies in agriculture, i.e. modifications in crop irrigation and cropping pattern, were also investigated. The results showed that by mid-century, precipitation will be reduced and temperature increased in the Zayandehroud river basin. The direct result of these changes will be a reduction in the basin discharge by 4.3 % in 2040 and 8.1 % in 2070 compared to the base period. The simulated economic value of water showed upward trends under climate change and socio-economic scenarios, reflecting an increase in water scarcity. In response to changes in the scarcity value of water, users respond by changing their patterns of water use and allocation. The withdrawal by each sector decreases in response to reduced runoff, although agriculture will be more responsive. The results of the PMP model showed that by choosing optimal cropping pattern and an optimum deficient-irrigation strategy for each crop, there will be good opportunities for farmers to adapt to increasing water scarcity and higher temperatures induced by climate change.

中文翻译：

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气候变化对伊朗 Zayandehroud 河流域水资源和农业的经济影响

摘要 气候变化对水资源和农业生产力产生巨大影响，尤其是在干旱和半干旱环境中。本研究模拟和探讨了 2040 年和 2070 年气候变化对伊朗 Zayandehroud 河流域水和农业部门的经济影响，分为三个主要阶段。在第一阶段，应用两个环流模型（GCM）（HadCM2 和 CGCM3T63）、人工神经网络（ANN）降雨-径流模型和作物-水生产函数来评估气候变化对水资源和各种农作物产量。在第二阶段，上述模型被整合到 Zayandehroud 盆地的水文经济空间平衡模型（HE-SEMZ）中，模拟的径流和社会经济变化对水部门的经济福利、其分配后果以及时空水价和分配的影响进行了模拟。在第三阶段，将模拟最优分配给农业部门的水引入农业部门的正数学规划（PMP）模型中，以模拟作物种植面积、种植方式和农民总收益的后续变化。在该建模框架中，还研究了两种无成本适应战略在农业中的作用，即作物灌溉和种植模式的修改。结果表明，到本世纪中叶，Zayandehroud 河流域降水将减少，温度将升高。这些变化的直接结果是，与基期相比，流域流量在 2040 年和 2070 年将分别减少 4.3% 和 8.1%。水的模拟经济价值在气候变化和社会经济情景下呈上升趋势，反映了水资源短缺的加剧。为了应对水资源稀缺价值的变化，用户通过改变他们的用水和分配模式来做出回应。每个部门的取水量随着径流减少而减少，但农业的反应会更快。PMP 模型的结果表明，通过为每种作物选择最佳的种植模式和最佳的缺水灌溉策略，农民将有很好的机会适应气候变化导致的日益严重的水资源短缺和更高的温度。与基期相比，2070 年为 1%。水的模拟经济价值在气候变化和社会经济情景下呈上升趋势，反映了水资源短缺的加剧。为了应对水资源稀缺价值的变化，用户通过改变他们的用水和分配模式来做出回应。每个部门的取水量随着径流减少而减少，但农业的反应会更快。PMP 模型的结果表明，通过为每种作物选择最佳的种植模式和最佳的缺水灌溉策略，农民将有很好的机会适应气候变化导致的日益严重的水资源短缺和更高的温度。与基期相比，2070 年为 1%。水的模拟经济价值在气候变化和社会经济情景下呈上升趋势，反映了水资源短缺的加剧。为了应对水资源稀缺价值的变化，用户通过改变他们的用水和分配模式来做出回应。每个部门的取水量随着径流减少而减少，但农业的反应会更快。PMP 模型的结果表明，通过为每种作物选择最佳的种植模式和最佳的缺水灌溉策略，农民将有很好的机会适应气候变化导致的日益严重的水资源短缺和更高的温度。反映了水资源短缺的加剧。为了应对水资源稀缺价值的变化，用户通过改变他们的用水和分配模式来做出回应。每个部门的取水量随着径流减少而减少，但农业的反应会更快。PMP 模型的结果表明，通过为每种作物选择最佳的种植模式和最佳的缺水灌溉策略，农民将有很好的机会适应气候变化导致的日益严重的水资源短缺和更高的温度。反映了水资源短缺的加剧。为了应对水资源稀缺价值的变化，用户通过改变他们的用水和分配模式来做出回应。每个部门的取水量随着径流减少而减少，但农业的反应会更快。PMP 模型的结果表明，通过为每种作物选择最佳的种植模式和最佳的缺水灌溉策略，农民将有很好的机会适应气候变化导致的日益严重的水资源短缺和更高的温度。