Abstract
The spatiotemporal distribution of critical source areas (CSAs) will change with hydrological conditions. In this study, the CSAs of nitrogen load under different hydrological conditions in the Chaohe River watershed were identified using the cumulative pollution load curve method determined from the nitrogen pollution simulated using the Soil and Water Assessment Tool (SWAT) model. The results showed that: (1) The order of factors impacting nitrogen load intensity is as follows: fertilization intensity, rainfall, runoff, land use type, slope type, and soil type. (2) The primary and secondary CSAs are concentrated in the upper and lower areas of the watershed, where cultivated land (8.36%) and grassland (52.55%) are more abundant. The potential pollution source areas are concentrated in the upper and middle areas of the watershed, where cultivated land (6.99%), grassland (42.37%), and forest land (48.18%) are evenly distributed. The low-risk source areas are concentrated in the middle and left bank of the watershed, where forest land (67.65%) is dominant and the vegetation coverage is highest. The research results have significance for improving the accuracy of the implementation of best management practices, and can provide a reference for the formulation of drinking water protection policies for Beijing.
Highlights
Non-point source (NPS) pollution refers to water pollution caused by dissolved or particulate pollutants from unspecified areas flowing into the receiving water body through runoff processes under the influence of precipitation [1]
The results showed that the Soil and Water Assessment Tool (SWAT) model can be successfully used to identify critical source areas (CSAs) in the watershed, and the simulation results of different data sets are different, which can provide a reference for the selection of data sets for future simulations in other regions
Strauss et al [50] configured the best management practices (BMPs) for two small watersheds in Austria and Italy, the results showed that the identification of CSAs of NPS pollution is critical to the configuration of BMPs
Summary
Non-point source (NPS) pollution refers to water pollution caused by dissolved or particulate pollutants from unspecified areas flowing into the receiving water body (such as rivers, lakes, reservoirs, and bays) through runoff processes under the influence of precipitation [1]. A large number of studies have shown that NPS pollution is the main cause of deterioration and eutrophication of surface water bodies such as rivers, lakes, and reservoirs [4,5,6]. Compared with point source pollution, the temporal and spatial difference in NPS pollution is obvious because of the characteristics of the varying sources, intermittent discharge, and random occurrence. It is more difficult, complicated and expensive to monitor, control, and manage
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