Climate change is one of the most important factors influencing the future of the world's environment. The most important impacts of climate change are changes in water supply and demand in different regions of the world. In this study, different climate change patterns in two RCP4.5 and RCP8.5 emission scenarios (RCP: Representative Concentration Pathway), were adopted for the Zayandeh-Rud River Basin, Iran, through weighting of GCMs (General Circulation Models). These climate change patterns are including ideal, medium, and critical patterns. Using the LARS-WG model (Long Ashton Research Station Weather Generator), the outputs of the GCMs were downscaled statistically and the daily temperature and precipitation time series were generated from 2020 to 2044. Then, based on this information, the inflow volume into the Zayandeh-Rud Reservoir was predicted by the IHACRES model (Identification of unit Hydrograph and Component flows from Rainfall, Evaporation and Streamflow) and the agricultural water demand was also estimated based on future evapotranspiration. Finally, using GAMS (General Algebraic Modeling System) software, water resources in this basin were allocated based on the basic management scenario (B) and the water demand management scenario (D). The results showed that the average monthly temperature will increase by 0.6 to 1.3 °C under different climate change patterns. On the other hand, on the annual basis, precipitation will decrease by 6.5 to 31% and inflow volume to the Zayandeh-Rud Reservoir will decrease by 21 to 38%. The results also showed that the water shortages based on the baseline management scenario (B) will be between 334 and 805 MCM (Million Cubic Meters). These range of values varies between 252 and 787 MCM in the water demand management scenario (D). In general, the water shortage can be reduced in the Zayandeh-Rud River Basin with water demand control, but complete resolution of this problem in this region requires more integrated strategies based on a sustainable development, such as a fundamental change in the cropping pattern, prevention of population growth and industrial development.

气候变化是影响世界环境未来的最重要因素之一。气候变化的最重要影响是世界不同地区的水供需变化。在这项研究中，通过对GCM进行加权（通用环流模型），在伊朗的Zayandeh-Rud流域采用了两种RCP4.5和RCP8.5排放情景（RCP：代表性浓度途径）中的不同气候变化模式。这些气候变化模式包括理想模式，中等模式和关键模式。使用LARS-WG模型（Long Ashton研究站天气生成器）对GCM的输出进行统计缩减，并生成2020年至2044年的每日温度和降水时间序列。然后，基于此信息，通过IHACRES模型（识别降雨，蒸发和水流的单位水位和成分流量）预测了Zayandeh-Rud水库的入水量，并基于未来的蒸散量估算了农业需水量。最后，使用GAMS（通用代数建模系统）软件，根据基本管理方案（B）和需水管理方案（D）分配该流域的水资源。结果表明，在不同的气候变化模式下，月平均温度将升高0.6至1.3°C。另一方面，按年计算，降水量将减少6.5％至31％，而Zayandeh-Rud水库的流入量将减少21％至38％。结果还表明，基于基准管理方案（B）的水资源短缺将在334至805 MCM（百万立方米）之间。在用水需求管理方案（D）中，这些值的范围在252和787 MCM之间变化。总体而言，可以通过控制用水量来减少Zayandeh-Rud流域的缺水，但是要彻底解决该地区的这一问题，就需要基于可持续发展的综合战略，例如种植方式的根本变化，预防人口增长和工业发展。