The impacts of spatio-temporal variation of natural and agricultural influences on the environmental water quality in a fluvial-lacustrine watershed in China

Despite the significant impacts of natural factors such as rainfall, topography, soil type, and river network as well as agricultural activities on the environmental water quality, little is known about the influence of their temporal and spatial variations in a fluvial-lacustrine watershed. In this study, a whole process accounting method based the export coefficient model (WP-ECM) was first developed to quantify how natural factors and agricultural activities distribution influenced water quality. A case study was performed in a typical fluvial-lacustrine area - Dongting basin, China. The simulated results indicated that the natural factors can promote and inhibit the migration and transformation of agricultural pollutants generated from the watershed and the spatial distribution of the natural factors displayed high variability. It should be priority to monitor the areas with greater natural impact in the basin. Moreover, the cultivated land area and the number of pig-breeding were positively correlated with the pollutant discharge. From the perspective of the spatial distribution of comprehensive influence, the comprehensive high-impact areas are mainly distributed in the Dongting Lake district in 2005-2010 and in Xiang River watershed in 2010-2020. A key strategy for controlling or reducing the cultivated land area and the intensity of livestock breeding in these high-impacts areas is recommended to reduce the impact of the environmental water quality for the entire basin.

Automated summary

This study developed a whole process accounting method based on the export coefficient model to quantify the influence of natural factors and agricultural activities on water quality. A case study in the Dongting basin, China showed that natural factors can promote or inhibit the migration and transformation of agricultural pollutants, with high spatial variability. Monitoring areas with greater natural impact in the basin is a priority. Cultivated land area and pig-breeding were positively correlated with pollutant discharge. The comprehensive high-impact areas were mainly located in Dongting Lake district during 2005-2010 and Xiang River watershed during 2010-2020. Controlling or reducing cultivated land area and livestock breeding intensity in these high-impact areas is recommended to mitigate the impact on environmental water quality in the entire basin.