河流干支流水质与土地利用的相关关系

为探索不同等级河流水质状况及其对土地利用构成响应的差异,以江苏北部的灌河流域为研究对象,基于2006—2007年两个年度灌河及其支流的水质监测数据和研究区的Landsat TM影像,在河流两侧长度0.0—10.0 km、宽度0.0—0.5 km的范围内,运用多元回归分析,对研究区干、支流主要水质指标及其与相应土地利用构成的关系进行了研究。结果表明:2006—2007年间,研究区干流水质总体上显著好于支流,支流的总氮(TN)、总磷(TP)等营养盐指标显著高于干流,而干流的有机污染指标显著高于支流;比较不同观测尺度上土地利用构成对河流水质变化的方差贡献率发现,缓冲区宽度一定时,支流在所有观测尺度上的土地利用构成与水质变化皆存在显著相关关系,而干流仅在缓冲区长度0.0—4.0 km的观测尺度上其土地利用构成与水质变化的相关关系显著;缓冲区长度一定时,干、支流河道两侧0.0—0.3 km间土地利用状况对水质变化的解释能力较大。同时发现,氮、磷等营养盐浓度多与较大尺度上的土地利用构成相关,而化学需氧量(COD)、生化需氧量(BOD)等多与较小尺度上的土地利用构成相关。研究结果显示,有必要区分不同河流等级,选择适宜的观测尺度,分别研究不同水质指标与土地利用构成间的相关关系。

Comparative analysis of correlation between water quality and land use pattern of different river hierarchies

Water quality deterioration has become a severe environmental problem across the world and has been an urgent concern for the public and government authorities. Non-point source (NPS) pollution caused by land use is recognized as one of the most important impacts on water quality; and agricultural land use is a major source leading to eutrophication. NPS pollutants transfer along river hierarchies and enter lakes/seas eventually. Hydrological processes and ecological characteristics usually vary by river hierarchy, as a result, water quality and land use could manifest various interactions, depending on level of river hierarchies and spatial scale of observation. Using monitoring data of water quality in 2006-2007 and contemporary Landsat TM images, we investigated the responses of water quality to riparian land uses, with respect to main streams vs. branches in Guan River Basin, north Jiangsu Province, China. Multiple linear regression models were used to examine the relationships at the scales ranging from 0.0 to 0.5 km in width and 0.0-10.0 km in length along the river channels. We found higher nutrient concentrations but lower organic pollutant concentrations in the branches than the main streams. The main streams showed significantly better water quality than the branches in dry seasons; while their difference was small in wet seasons. With fixed buffering widths, water quality of the main streams had significant correlations with land use only at relatively small (i.e. 0.0-4.0 km) buffering lengths; while for the branches, the correlations were significant at all buffering lengths. With fixed buffering length, the largest variance in water quality was explained by the land use within 0.3 km of the river channels for all the main streams and branches. The concentrations of TN (Total Nitrogen) and TP (Total Phosphorus) were related to land use mostly on larger scales, while such relation was observed only on smaller scales for organic pollutants. The result indicated that it is necessary to study the correlations between land use and water quality in each river system hierarchy, respectively, at appropriate scales.