膨胀性土壤变形滞后性对入渗产流影响机理及模型改进

Swelling soils are widely distributed. Absorbing water and expansion, dehydration and shrinkage, the deformation process of wetting expansion and drying shrinkage has hysteresis in swelling soils. The swelling soils deformation hysteresis has great influences on infiltration and runoff process. Studying on mechanism of swelling soils deformation hysteresis influences on soil infiltration and runoff can provide proof for soil water management, water and soil resources optimal regulation. The researches in swelling soils deformation hysteresis influences on soil infiltration and runoff are not yet reported. Based on soil water movement parameters determination test, artificial tracer tracing test, rainfall-infiltration-runoff test and soil water movement dynamic determination test, the swelling soils deformation hysteresis influences on soil infiltration and runoff are quantitatively analyzed. The project is to reveal the mechanism of soil infiltration and runoff influenced by swelling soil deformation hysteresis. Based on the understanding on the mechanism, the infiltration and runoff model considered soil deformation hysteresis will be established, and verified with the experiments data. Based on verified model, the distributed watershed hydrological model with the consideration of the influences of the soil deformation hysteresis will be established and verified in a typical watershed (Buha river basin in Qinghai Lake). Finally, the soil infiltration and runoff influenced by swelling soil deformation hysteresis will be analyzed. It is aimed to improve the runoff simulation distortion and accuracy in watersheds through this study.

膨胀性土壤分布广泛，土壤湿胀干缩，湿胀干缩变形过程具有滞后性。膨胀性土壤变形滞后性极大地影响着土壤入渗产流过程，研究膨胀性土壤变形滞后性对土壤入渗产流过程影响机理，可以为土壤水分管理、水土资源优化调控提供科学依据。膨胀性土壤变形滞后性对土壤入渗产流过程影响研究尚未报道。本项目拟通过土壤水分特征参数测定试验、人工示踪剂示踪试验、降雨入渗产流试验和土壤水分动态过程监测试验，定量分析膨胀性土壤变形滞后性对土壤入渗产流过程影响，揭示膨胀性土壤变形滞后性对土壤水分入渗影响机理。基于机理认识，提出考虑膨胀性土壤变形滞后性的土壤入渗产流模型，并通过室内试验观测数据验证模型的可靠性和适用性。在此基础上，建立考虑膨胀性土壤变形滞后性的分布式水文模型，并在典型流域（青海湖布哈河流域）进行率定和验证，并就膨胀性土壤变形滞后性对流域产汇流过程影响做出定量分析，以实现改善模拟失真，提高流域径流模拟精度的研究目标。

膨胀性土壤是一种广泛分布于世界各地的特殊土壤类型，具有独特的胀缩特性，对土壤水分运动有很大影响。针对膨胀性土壤变形（垂向和横向）对入渗产流影响机理研究，项目研究过程中首先开展了大量实验研究，包括土壤水分特征参数测定试验、降雨入渗产流试验等，其中水分特征参数测定试验是为了便于后期各种试验分析。在此基础上，确定了土壤膨胀变形与土壤入渗能力之间的关系，进而提出了膨胀性土壤垂向变形的水动力模型（GRID）和两流区水动力学模型（GDPM），并对模型进行了试验验证。结果表明：通过量化土壤膨胀垂向变形对水分运动过程的影响，GRID模型可以较好地模拟计算土壤累计入渗量和径流强度。同时，通过考虑土壤膨胀力、自重应力和土壤含水量对土壤变形的影响， GDPM模型计算的径流强度和累积入渗与实测值吻合较好。在此基础上，通过考虑垂向变形过程，改进了WEP分布式水文模型入渗产流模块和土壤水分再分布模块，构建了考虑土壤膨胀性的流域分布式水文模型，并以青海湖布哈河流域为典型流域，进行了模型应用研究，通过模型应用确定流域尺度降水—地表水—土壤水间转化关系。项目研究成果对农田土壤水分动态过程，以及流域水文过程预测具有重要意义。