Surface runoff modeling for Xitiaoxi catchment, Taihu Basin

Abstract

西苕溪是太湖集水域的一个主要流域,研究西苕溪流域径流过程及污染物产出对了解太湖水文水质变化以及开展周围其它流域研究工作具有重要意义．作为研究的第一步,采用集总式模型LASCAM建立了西苕溪流域径流模型．以流域内2个水文观测站1968-1988年日径流观测数据对模型作了率定．率定效果满意,模拟日、年径流量与观测值吻合良好．在流域资料不够充分的情况下,模型能获得较为理想的模拟效果,说明所采用的模型适用于数据不足区域．模拟还揭示,西苕溪流域径流产生可能以饱和地面径流机制为主．近河道浅层饱和土体的水位与降雨量相关性好,呈现出明显的日波动周期;而深层地下水位呈年波动周期,在旱季和雨季,水位呈明显的降落和上升趋势．这些发现为进一步细化径流模型以及建立污染物输移模型奠定了基础．;Investigation on surface runoff and associated mass transport for Xitiaoxi catchment is of significant importance as it is one of the major catchments of Lake Taihu basin. Outcomes from this investigation help understand the dynamic changes of hydrology and water quality of lake Taihu，and are also useful in carrying out similar research work on other catchments of lake Taihu basin. As the first step, this paper presents the construction of a surface runoff model for Xitiaoxi catchment using a conceptual model, LASCAM. The model is well calibrated using daily runoff data from 1968-1988 from 2 monitoring stations within the catchment. The modeled daily and annual runoffs match well with the observed ones. The model indicates that saturation excess runoff is probably the dominant process for the catchment. Water storage in near-stream shallow saturated soil has high correlation with daily rainfall, while water storage changes in deep aquifers demonstrate an annual change period，showing a rising level for wet seasons and a declining level for dry seasons. The findings are helpful for further refining the runoff model and constructing nutrients transport model as the next step.