[Effect of meteorological factors on design farmland drainage modulus.]

Calculation of design drainage modulus is of great importance for the safety of farmland and reduction of waterlogging loss. We investigated the effects of main meteorological factors on design farmland drainage modulus by focusing on a closed farmland area in Ninghe District of Tianjin City. To resolve the problem of limited observation, the parameter sensitivity was analyzed according to mutual information and partial rank correlation coefficient aiming at the total runoff depth based on field observation experiment. The reasonable parameters were obtained by combining with soil water content and the relative variation of groundwater level. Then, a three-source runoff yield model coupling of excess infiltration and saturation was established to estimate runoff and design drainage modulus, and the effects of meteorological factors such as precipitation and evaporation on drainage modulus were analyzed. Results showed that summer precipitation significantly reduced and evaporation varied a little during 1960-2015. The corresponding drainage modulus decreased with the reduction of precipitation. When return period increased, the magnitude of the reduction in precipitation as well as the design drainage modulus increased. However, the effects of meteorological factors on design drainage modulus was generally inapparent. Thus, we concluded that the current drainage modulus is suitable for the study area.设计排涝模数的计算对农田安全和有效降低涝灾损失意义重大.本文选取天津市宁河区封闭农田小区为研究对象,分析了主要气象因子对农田设计排涝模数的影响.为解决观测样本有限的问题,在现场观测试验的基础上,以总径流深为目标,使用互信息、偏秩相关方法分析了参数敏感性,结合土壤含水量、地下水位相对变化量得到了合理的模型参数,建立了三水源超渗-蓄满耦合产流模型,进行了产流量和设计排涝模数估算,并分析了降雨和蒸发等气象因子对设计排涝模数的影响.结果表明: 1960—2015年,研究区夏季降水量显著减少,蒸发量变化不明显.排涝模数随降水量减少而减少,且随着设计重现期的增大,降水和设计排涝模数的减少量均有所增大,但总体来讲,气象因子对设计排涝模数的影响并不大,现行设计排涝模数可不进行修订.