High water consumption and inefficient irrigation management in the agriculture sector of the middle and lower reaches of the Amu Darya River Basin (ADRB) have significantly influenced the gradual shrinking of the Aral Sea and its ecosystem. In this study, we investigated the crop water consumption in the growing seasons and the irrigation water requirement for different crop types in the lower ADRB during 2004–2017. We applied the FAO Penman-Monteith method to estimate reference evapotranspiration (ET0) based on daily climatic data collected from four meteorological stations. Crop evapotranspiration (ETc) of specific crop types was calculated by the crop coefficient. Then, we analyzed the net irrigation requirement (NIR) based on the effective precipitation with crop water requirements. The results indicated that the lowest monthly ET0 values in the lower ADRB were found in December (18.2 mm) and January (16.0 mm), and the highest monthly ET0 values were found in June and July, with similar values of 211.6 mm. The annual ETc reached to 887.2, 1002.1, and 492.0 mm for cotton, rice, and wheat, respectively. The average regional NIR ranged from 514.9 to 715.0 mm in the 10 Irrigation System Management Organizations (UISs) in the study area, while the total required irrigation volume for the whole region ranged from 4.2×109 to 11.6×109 m3 during 2004–2017. The percentages of NIR in SIW (surface irrigation water) ranged from 46.4% to 65.2% during the study period, with the exceptions of the drought years of 2008 and 2011, in which there was a significantly less runoff in the Amu Darya River. This study provides an overview for local water authorities to achieve optimal regional water allocation in the study area.

中文翻译：

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中亚阿姆河下游流域作物蒸散量和灌溉需水量调查

阿姆河流域（ADRB）中下游农业部门的高耗水和低效灌溉管理显着影响了咸海及其生态系统的逐渐萎缩。在这项研究中，我们调查了 2004-2017 年期间 ADRB 下不同作物类型在生长季节的作物耗水量和灌溉用水需求。我们应用粮农组织 Penman-Monteith 方法根据从四个气象站收集的每日气候数据估算参考蒸散量 (ET0)。特定作物类型的作物蒸散量 (ETc) 由作物系数计算。然后，我们根据有效降水和作物需水量分析了净灌溉需求 (NIR)。结果表明，较低的 ADRB 月 ET0 值最低出现在 12 月（18.2 毫米）和 1 月（16.0 毫米），最高月度 ET0 值出现在 6 月和 7 月，相似值为 211.6 毫米。棉花、水稻和小麦的年 ETc 分别达到 887.2、1002.1 和 492.0 mm。研究区 10 个灌溉系统管理机构 (UIS) 的平均区域 NIR 范围为 514.9 至 715.0 mm，而 2004-2017 年整个区域所需的总灌溉量范围为 4.2×109 至 11.6×109 m3。在研究期间，SIW（地表灌溉水）中 NIR 的百分比范围为 46.4% 至 65.2%，但 2008 年和 2011 年的干旱年份除外，其中阿姆河的径流明显减少。