中文摘要：

通过控制排水措施适当提高地下水位,可以增加半湿润灌区作物对浅层地下水的利用量,缓解灌溉水量的不足。然而,灌区地下水的含盐量一般较高,对盐分在作物根区的过分累积,所需淋洗水量很难得到保证。考虑到半湿润灌区具有一定量的降雨,可能对土壤盐分产生淋洗作用,建立了一个控制排水条件下降雨洗盐计算模型,并以某半湿润灌区盐碱地改良区为例,利用田间水文模型DRAINMOD预测出多年（1951—2005）田间水量平衡逐日变化过程,连续计算控制排水以及不同补充灌溉条件下根层土壤盐分多年的动态过程。结果显示,当地下水控制埋深为1.2 m时,在无灌溉条件下,研究区降雨虽能起到一定的淋洗作用,但根区盐分会随着时间的推移逐渐累积。当补充灌溉量在150 mm以上时,研究区降雨能够有效控制土壤盐分,使根区土壤在多年条件下达到良性的水盐平衡。所以,在与研究区类似的半湿润地区,通过控制排水措施合理调控地下水埋深,并充分利用天然降雨的淋洗功能,不仅可以维持灌区良性的水盐平衡,而且可以提高水资源利用效率。

英文摘要：

Properly raise water table with controlled drainage may increase shallow groundwater which canbe used by crops,mitigating the water shortage in subhumid irrigated areas. However,salinity in groundwa-ter over there is generally higher,and increasing use of shallow groundwater may speed up salt accumula-tion in the root zone and shorten the salt leaching cycle;this is not desired in these areas because theleaching water can hardly be ensured during the required period. Considering in the subhumid irrigation ar-eas there are certain amount of rainfall that may produce leaching effect for salinity control,an analyticalmodel was developed for calculating salt leaching cycle under controlled drainage. The model was testedsubsequently through a case study in a subhumid irrigation area in which soil was reclaimed from saliniza-tion. With the daily water balance predicted by the field hydrology model-DRAINMOD,we calculated thesalt accumulation in the root zone over a long term period（1951-2005） under controlled drainage and dif-ferent supplemental irrigation depths. The results show that when groundwater depth is controlled at 1.2 m,rainfall has some effect on salt leaching even without irrigation;but soil salinity grows with time in theroot zone. When the supplementary irrigation depth is greater than 150 mm,rainfall can effectively controlthe root zone salinity to reach a favorable salt balance in the case study area. Findings from this researchindicate that in subhumid irrigation areas, considering the leaching effect of rainfall, proper water tablemanagement with controlled drainage can effectively control soil salinity for crop production and improve wa-ter use efficiency.