Capillary rise from shallow groundwater can decrease the need for irrigation water. However, simple techniques do not exist to quantify the contribution of capillary flux to crop water use. In this study we develop the Agricultural Water Productivity Model for Shallow Groundwater (AWPM-SG) for calculating capillary fluxes from shallow groundwater using readily available data. The model combines an analytical solution of upward flux from groundwater with the EPIC crop growth model. AWPM-SG was calibrated and validated with 2-year lysimetric experiment with maize. Predicted soil moisture, groundwater depth and leaf area index agreed with the observations. To investigate the response of model, various scenarios were run in which the irrigation amount and groundwater depth were varied. Simulations shows that at groundwater depth of 1 m capillary upward supplied 41% of the evapotranspiration. This reduced to 6% at groundwater depth of 2 m. The yield per unit water consumed (water productivity) was nearly constant for 2.3 kg/m3. The yield per unit water applied (irrigation water productivity) increased with decreasing irrigation water because capillary rise made up in part for the lack of irrigation water. Consequently, using AWPM-SG in irrigation scheduling will be beneficial to save more water in areas with shallow groundwater.
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机译:浅层地下水中的毛细管上升可以减少对灌溉水的需求。但是,没有简单的技术可以量化毛细管通量对作物用水的贡献。在这项研究中,我们开发了用于浅层地下水的农业用水生产率模型(AWPM-SG),该模型使用现成的数据来计算浅层地下水的毛细通量。该模型将地下水上升通量的分析解决方案与EPIC作物生长模型相结合。对AWPM-SG进行了为期2年的玉米溶干试验的校准和验证。预测的土壤湿度,地下水深度和叶面积指数与观测值一致。为了研究模型的响应,运行了各种情况,其中灌溉量和地下水深度有所不同。模拟表明,在地下水深度为1µm时,毛细管向上提供了41%的蒸散量。在2µm的地下水深处,这一比例降至6%。单位耗水量(水生产率)为2.3 kg / m 3 sup>几乎恒定。单位灌溉用水量(灌溉水生产率)随灌溉水的减少而增加,这是因为毛细血管的上升部分是由于灌溉水的缺乏所致。因此,在灌溉调度中使用AWPM-SG将有利于在地下水较浅的地区节省更多的水。
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