基于SWAT模型的太湖西北部30a来氮磷的输出特征

CHARACTERISTICS OF NITROGEN AND PHOSPHORUS LOAD IN THE PAST THREE DECADES IN THE NORTHWEST OF TAIHU BASIN BASED ON THE SWAT MODEL

随着工业的迅速发展和农业生产方式的转变,使得太湖富营养化现象日趋严重,对流域内生态环境构成极大的威胁。以研究区6个时期土地利用数据和30a逐日降雨数据为模型的主要输入变量,利用SWAT模型分别对研究区内6个不同时期营养盐输出进行模拟研究,得到研究区内30a时间尺度(1984~2013年)营养盐输出情况。根据模型输出结果探究研究区内营养盐输出与降雨量、径流量以及土地利用变化的关系。以2009~2013年宜兴站径流数据和水质数据作为模型的率定和验证数据,总氮(TN)和总磷(TP)在模型率定期确定系数R2为0.76和0.92,纳什效率系数Ens为0.76和0.79,验证期确定系数R2为0.66和0.95,纳什效率系数Ens为0.6和0.54,模拟结果较好。结果表明:营养盐输出与降雨在时间是呈现较强的相关性,但是在空间上降雨与营养盐输出相关性不明显;土地利用类型与营养盐输出密切相关,耕地和建设用地是研究区主要的营养盐输出源,土地利用类型空间分布与TN、TP空间分布相关系数分别为0.74和0.73。将为太湖流域非点源污染控制和治理提供理论支撑及数据基础。

With the rapid development of industry and transformation of agricultural production, the phenomenon of eutrophication in Taihu Basin is becoming more and more serious, which poses a great threat to the ecological environment in the basin. This paper used land use data of six periods and daily rainfall data from 1984 to 2013 as the main input variables in the model. According to the land use data, we divided the time interval into six time periods. With the SWAT model （the Soil and Water Assessment Tool which can simulate soil water sediment and nutrient） to simulate the nutrients export in the study area of these six different periods, we calculated nutrients export in the past three decades （1984–2013） in the northwest of Taihu Basin. According to the model results, we explored the relationship between nutrients export, rainfall, runoff and the land-use change. The data of runoff and water quality recorded by the Yixing water station from 2009 to 2013 was used to calibrate and validate the model. The coefficient of determination R2 of total nitrogen and total phosphorus in calibration period was 0.76 and 0.92, respectively. The Nash coefficient of total nitrogen and total phosphorus was 0.76 and 0.79, respectively. The coefficient of determination R2 in the validation period was 0.66 and 0.95 and the Nash coefficient was 0.6 and 0.54, respectively. The results suggest that nutrients export was significantly correlated with the amount of rainfall and runoff over time, which were mainly concentrated in May to August every year, and were low in November to February of next year. However, this correlation was not significant in the space. Nutrients export was closely related to land use types, and the main nutrients export in the study area was concentrated in urban lands and agricultural lands. Agricultural lands were the main source of nutrients in the study area, but the flux of nutrients export in urban lands was higher than that in agricultural lands. The types of land use in study area showed a pattern of wasteland 〉 urban land 〉 agricultural land 〉 forest in terms of flux of nutrients export. The spatial distribution of nutrients export was also closely related to the spatial distribution of land use types. The export of nutrients in urban lands and agricultural lands was relatively higher than other land uses. This study will provide theoretical support and data base for the control and management of non-point source pollution in Taihu Basin.