基于数字栅格的河网小流域水质数学模型构建与应用

Development and Application of Water Quality Mathematical Model for Small Watershed in River Network Region Based on DEM Raster

摘要:

河网地区降雨充沛，河道水质受点源排放和降雨径流面源污染排放影响出现时空动态变化。针对小流域水质达标评估的需求，构建了基于栅格化空间重力汇水流向的降雨径流污染模型，并通过耦合河道水动力水质模型，建立点源、面源排放与河道水质的动态响应关系。以我国常州市武进港小流域为研究区域，对该模型系统进行了率定，确定了水质模型的主要参数。建立的模型系统能够实现对河网水质日尺度的动态模拟，继而实现从年均水质达标到每日水质达标的精细化分析。针对研究区域污染源组成特点，对不同污染负荷削减方案进行模拟评估。最优工况下，入湖断面高锰酸盐、氨氮和总磷的年达标频次（地表水III类标准）分别从23.0%、0、16.4%升高至71.8%、66.3%、75.9%。

Abstract:

Due to the abundant rainfall in river network region， the river water quality shows a temporal-spatial dynamic change affected by the point pollution and precipitation-runoff nonpoint pollution discharge. In order to assess the attainment of river water quality in small watershed， a nonpoint pollution model based on digital elevation model （DEM） raster was developed. Coupled with the hydrodynamic and water quality model， the dynamic river water quality response to point pollution and nonpoint pollution discharge was established. The modeling system was calibrated and the main water quality parameters were determined in the small watershed of Wujing River catchment in Changzhou， Jiangsu province. The modeling system developed is able to perform dynamic simulation of water quality in river network on daily scale， and realize an elaborate analysis from annual average attainment to daily attainment. According to the characteristics of regional pollution sources in the site studied， different pollutant load reduction schemes were simulated and evaluated. Under the optimal conditions， throughout the whole year， the frequency of attaining Grade III of surface water quality standard at lake inflow station would increase from 23.0%， 0， 16.4% to 71.8%， 66.3%， 75.9% for COD_Mn， NH₃-N， and total phosphorus （TP） respectively.