河套灌区耕地-荒地-海子系统间不同类型水分运移转化

Study on migration of different types water during farmland-wasteland-lake system in Hetao Irrigation District

为了探明耕地-荒地-海子系统中不同类型水分的运移转化规律,在2018—2019年典型时期对系统内具有代表性的采样点进行水样采集,分析了不同时期内不同水体的δ18O变化特征,并利用二端元混合模型和土壤水动力学方法计算了不同类型水分转化贡献率。结果发现:(1)在灌溉期,82%的灌溉水储存于1 m土体中,18%的灌溉水通过渗漏补给了耕地地下水,渠系灌溉水通过地下侧向径流给耕地地下水贡献了76%。(2)灌溉水和降雨对耕地地下水平均贡献率为94%和6%;耕地地下水和降雨对荒地地下水的平均贡献率为71%和29%;荒地地下水和降雨对海子的平均贡献率为43%和57%。(3)渠系灌溉水通过侧向径流贡献给耕地地下水的水量基本全部迁移给了荒地地下水,地下水迁移转化是由渠系水侧向径流触发的。(4)灌后5 d,耕荒地交界土层0~40 cm存在饱和-非饱和侧向补给;灌后15 d和30 d,耕地和耕荒地交界处的地下水向根区40~60 cm、土层80 cm以及100 cm补给水分;灌后30 d,耕地中的灌溉水水分消失。(5)在非灌溉期,荒地地下水和海子耗水较多,应给海子补给水分。

In order to find out the migration and transformation regularity of different types of water in cultivated land-wasteland-lake system,water samples were collected from representative sampling points in the system during the typical period from 2018 to 2019.Theδ18O variation characteristics of different types water in different periods were analyzed,and the contribution rate of different types of water transformation was calculated by two-terminal element mixed model and soil hydrodynamics theory.The results showed that during the irrigation period,82%of the irrigation water was stored in 1 m soil,18%of the irrigation water recharged the groundwater of cultivated land through leakage.76%of the irrigation water of canal system contributed to the groundwater of cultivated land through underground lateral runoff.The average contribution rate of irrigation water and rainfall to cultivated land groundwater was 94%and 6%,respectively.The average contribution rates of cultivated land groundwater and rainfall to wasteland groundwater was 71%and 29%,respectively.The average contribution rate of wasteland groundwater and rainfall to lake was 43%and 57%,respectively.The amount of water contributed by canal system irrigation water to cultivated land groundwater through underground lateral runoff was basically transferred to wasteland groundwater.The transfer and transformation of groundwater was triggered by canal system water lateral runoff.The 5th day after irrigation,saturated-unsaturated lateral recharge existed in 0—40 cm soil layer at the junction of cultivated land and wasteland.The 15th day and 30th day after irrigation,groundwater of cultivated land and the junction of cultivated land and wasteland recharged soil water in 40—60 cm(root zone),80 cm and 100 cm soil layer.The 30th day after irrigation,the irrigation water in the cultivated land disappeared.In non-irrigation period,wasteland groundwater and lake were consumed much water.Therefore,lake should be recharged water.The calculation results were demonstrated with relevant research,which were reliable and can provide important reference for water resources analysis of cultivated land-wasteland-lake system.