基于种植结构改进的SWAT模型模拟乌梁素海流域面源污染负荷

Simulation of non-point source pollution load in Ulansuhai watershed by SWAT model based on improved planting structure

乌梁素海是黄河流域最大的湖泊湿地,其地处河套灌区,是灌区排水的承泄湖。多年来面临着严重的水生态系统功能退化、水环境污染等问题,而改善和治理湖泊水环境的基础是要厘清乌梁素海流域灌区退水导致的农业面源污染负荷问题。基于无人机获取的高分辨照片与遥感影像和地面实测数据相结合所获取的精准种植结构数据可作为SWAT模型输入的土地利用数据,以确保对农业面源污染迁移转化过程的模拟更接近真实情况。结果表明,基于作物种植结构数据对流域径流模拟精确度较高,率定期R^(2)为0.74,NES为0.81,验证期R^(2)为0.78,NES为0.67。TN和TP在2010—2020年间整体呈逐渐下降的趋势。季节分析发现,TN和TP均表现为春季负荷量较高。空间分布表明,乌梁素海流域总氮年均负荷量在南部的河套灌区较高,北部草原区较低,在流域东部番茄、瓜果、甜菜等经济作物集中分布的区域,TN负荷量为30~45 t·a^(-1);总磷污染物负荷量的空间分布与总氮基本一致,主要分布在以玉米和葵花为主的子流域,TP年均总输出量均超过10 t·a^(-1)。本研究结果可为乌梁素海流域面源污染治理及种植结构调整提供参考。

Ulansuhai,as the largest ecological functional area in north China,has been faced with serious problems of water ecosystem function degradation and water environment pollution for many years.The basis of improving and controlling the lake water environment was to clarify and solve the non-point source pollution caused by irrational irrigation and farming in Ulansuhai Watershed.Based on the SWAT model,this paper combined the high-resolution photos obtained by Unmanned Aerial Vehicle with remote sensing images and ground measured data as the land use data input by the SWAT model to ensure that the simulation of the migration and transformation process of non-point source pollution was closer to the real situation.The results showed that the simulation accuracy of runoff was high based on crop planting structure data,and the preheating period R^(2)was 0.74,NES was 0.81,and the verification period R^(2)was 0.78,NES was 0.67.TN and TP showed a gradual decline from 2010 to 2020.The seasonal analysis showed that both TN and TP showed a higher load in spring.The spatial distribution showed that the average annual load of total nitrogen in the Ulansuhai Watershed was higher in the southern Hetao irrigation area,but lower in the northern grassland.In the eastern part of the basin,where tomato,melon,fruit,beet and other crops were concentrated,TN load was 30-45(t·a^(-1)),and the spatial distribution of total phosphorus pollutant load was basically consistent with that of total nitrogen.It was mainly distributed in the sub-basins of corn and sunflower,and the annual total output of TP exceeds 10(t·a^(-1)).The results of this study can provide theoretical basis for non-point source pollution acontroll and planting structure improvement in Ulansuhai watershed.