根据排水规律计算稻田节水的潜力

针对宁夏银南灌区农业水评价中缺乏详细排水分析的不足，该文从盐分淋洗需求、灌溉-排水的转化过程以及节水的可行性等方面，对稻田的田间节水潜力进行了分析和计算，同时，该文提出由于不同形式的排水(地下、地表)在盐分淋洗上存在的根本差异，在分析流域是否存在排水过量时应该区别对待；而灌区目前存在的、相对稳定的深层地下排水提供了一定的内在淋洗能力，农沟排水只需要补充不足的部分。计算结果表明：深层排水提供的182 mm淋洗水量，形成了0.16的淋洗率；与需要的临界淋洗水量343 mm相比(淋洗率0.31)，尚需要农沟提供161 mm的排水量。灌区现状农沟排水量为445 mm，可以减少284 mm；加上应该削减的地表径流(309 mm)，田间节水潜力为593 mm。对于银南灌区22333 hm²的种植面积，一年可节水量为1.32亿m³。以目前灌区0.45的渠系利用率计，可减少引水2.94亿m³。

Estimating water saving potential based on drainage analysis

Detail drainage analysis seriously influences evaluation of agricultural water resource in the Yinnan Irrigation District. According to the salt leaching requirement, transformation process of irrigation-drainage and feasibility of water saving, water saving potential of rice field was estimated and analyzed. Because of the difference in salt leaching effect between surface and subsurface drainage, the estimation method of irrigation drainage is different. Existing and relative steady deep subsurface drainage supplies a certain leaching capacity, and ditch drainage only needs to supply the shortage part. The results show that the deep subsurface drainage provids 182 mm leaching water, and leaching fraction is 0.16. Compared with the critical value of leaching fraction 0.31, or leaching depth of 343 mm required for the area, only 161 mm additional leaching water is needed. For the current rice growing area of 22333 hm² and ditch drainage volume of 445 mm, 284 mm may be reduced. In addition to the surface runoff of 309 mm, the potential of water saving from rice fields is 593 mm, or 132 million m³ in total volume, which is equivalent to 294 million m³ reduction in irrigation diversion from the Yellow River considering a canal conveyance efficiency of 0.45 in the Yinnan Irrigation District.