降雨径流过程的非点源污染时空动态分布研究

Study on Spatial Distribution of Non-point Source Pollution in the Process of Rainfall Runoff

构建一种基于元胞自动机(CA)的降雨-径流模拟模型,以储水系数增加率、坡度、坡向、土地利用类型和降雨强度作为输入参数,DEM数据作为元胞空间,建立地表径流由高向低流动的转换规则,并将模型与GIS技术集成,得到不同时刻栅格上的径流深和流量。在此基础上建立污染物浓度与流量、降雨强度和累积降雨量的回归模型,得到不同时空的污染物浓度变化情况。以汉江中下游流域为例,模拟发现河流或湖泊的栅格点往往在单次降雨过程中的径流较深;同时,降雨流量的大小与地形坡度相关性明显,在坡度较大的区域降雨流量也较大。以汉阳单场降雨为例,构建污染物影响机制,并将其推广到汉江中下游,得到整个汉江中下游的污染物分布情况。结果表明,在降雨初期污染物的浓度随机性很大,同时土地利用类型对污染物浓度的影响也较大。

A cellular automata（CA）-based model is proposed to simulate the process of runoff-rainfall,taking storage coefficient,slope,aspect,land use types and rainfall intensity as inputs,the DEM as the simulating space,the flowing pattern from high to low surfaces as the transformation rules. It is integrated with geographic information system（GIS）to get runoff depth and quantity of flow from lattice cells at different time and space. Taking the middle and downstream of Han River as an example,the CA simulating results shows that the water body always undergoes high depth in a single rainfall process. Meanwhile,the quantity of the flow relies on the slope largely so that the cell with larger slope tends to own considerable flow. Then the single rainfall in Hanyang,Wuhan was used to establish pollutant influence mechanism and to extract the distribution circumstances in the middle and downstream of Han River. The spatiotemporal distribution of non-point source pollution indicates that the pollutant loads are in great random at the preliminary stage of the rainfall,and the land use type has a significant influence on pollutant loads.