分布式水文模型在岩溶地区的改进与应用研究

Improvement and application of a distributed hydrological model in karst regions

在我国西南岩溶峰林地区,碳酸盐岩岩溶的强烈发育使含水层空间结构具有高度非均质性,加之表层岩溶带对降雨入渗的影响,导致传统的含水层高度概化的水文模型难以定量刻画地表水对地下水的补给过程。文章在开源的SWAT(土壤和水评估工具)模型基础上,通过改进土壤水及地下水模块,刻画水分经表层岩溶带以慢速流和快速流的方式进入含水层的过程,分别以活塞式推进方式及以捷径式入流方式进入浅层含水层,构建了适应于岩溶地区的分布式水文模型。以桂林市漓江流域为例,在碳酸盐岩和碎屑岩交叉分布的流域建立水文模型,并对构建的模型进行率定与验证,结果表明:与原模型径流模拟相比,本文构建的模型较好体现了表层岩溶带的调蓄作用,改善了各水文站枯水期模拟较差的情况(其中潮田站纳什系数由0.78提高到0.92,决定系数由0.85提高到0.92,比改进前有明显提高);改进后的模型能适用于碎屑岩与碳酸盐岩分布不均的岩溶流域水分循环模拟。

In the karst peak forest area of southwest China,it is difficult to quantitatively characterize the process of groundwater recharge with the traditional hydrogeological models due to the spatial heterogeneity caused by the strong carbonate karst development and the influence of surface karst zone on rainfall infiltration.Based on the open-source SWAT(Soil and Water Assessment Tool)model and by improving the soil water and groundwater modules,the process of soil water entering groundwater through rapid flow and slow flow respectively by piston propulsion and by shortcut,is characterized in this paper.Taking the Lijiang River Basin in Guilin of Guangxi as an example,the authors establish a hydrological model in the basin with the cross distribution of carbonate and clastic rocks,and the model is calibrated and validated.The results show that compared with the original model,the distributed model has a better efficiency on simulation of regulation and storage function of the surface karst zone and dry season simulation in each hydrological station.The Nash coefficient of the Chaotian station increases from 0.78 to 0.92,and the determination coefficient increases from 0.85 to 0.92,obviously higher than that before the improvement.The improved model can be applied to the simulation of water cycle in karst basins with uneven distribution of clastic rocks and carbonate rocks.