Evaluating long-term hydrological impacts of regional urbanisation in Hanyang,China, using a GIS model and remote sensing

China has experienced a rapid urbanisation, especially since the 1980s; however, the environmental impacts of this process are not fully investigated. Hanyang (Hubei Province, south China) was selected as a typical case to investigate runoff and non-point source (NPS) pollution impacts of urbanisation. A water quality simulation model (L-THIA) was applied to determine the long-term implications of different degrees of regional urbanisation impacts on NPS pollutants. Land-use patterns in 1987, 1998 and 2003 were analysed to evaluate the temporal variation of urbanisation, and the precipitation dataset from 1975 to 2003 was used to estimate the mean annual runoff and NPS pollutants. The contributions of different land-use categories to average annual runoff and NPS pollutant production were assessed by the means of a regression model. Results show that urban/impervious lands increased by 30.4% between 1987 and 2003, with the most increase occurring in 1998–2003. Industrial and forestlands have the most and least impact, respectively, on mean annual runoff and NPS pollutants. A combination of L-THIA and the regression model was found to be useful as a decision support tool for regional and urban planning from the perspectives of water quality control.     

基于L-THIA模型的市桥河流域非点源氮磷负荷分析

以番禺市桥河流域为研究对象,利用现场建立的不同土地利用类型的径流场实测降雨径流数据,对长期水文影响评价模型(L-THIA)的主要参数进行校正,模拟计算该流域非点源氮磷负荷量,并分析土地利用和降雨变化对氮磷负荷输出的影响.结果表明,市桥河流域内非点源氮磷污染高负荷区主要集中在农业用地和城镇用地,单位面积污染负荷输出最高的为农业用地.从1995~2010年,流域非点源氮磷负荷呈增加趋势,TN增加了17.91%,而TP的增加幅度达到了25.30%.随着流域城镇化的迅速发展,城镇用地明显增加,所占比例达到了43.94%,2010年对负荷总量的贡献率也已超过40%,几乎与农业用地持平,这也是近15年来流域内农业用地面积虽然有所降低,但污染负荷总量仍然增加的主要因素.流域内降雨主要集中在汛期,因而汛期非点源氮磷负荷亦远高于非汛期,占全年比例超过了85%.不同降雨类型发生次数与污染负荷的Pearson相关分析表明,日降雨量大于20 mm的降雨是造成流域内非点源氮磷污染的主要降雨类型.