Abstract
The extent of anthropogenic land use in watersheds determines the amount of pollutants discharged to streams. This indirectly and directly affects stream water quality and biological health. Most studies have therefore focused on ways to reduce non-point pollution sources to streams from the surrounding land use in watersheds. However, the mechanistic pathways between land use and the deterioration of stream water quality and biological assemblages remain unclear. This study estimated a structural equation model (SEM) representing the impact of agricultural and urban land use on water quality and the benthic macroinvertebrate index (BMI) using IBM AMOS in the Nam-Han river systems, South Korea. The estimated SEM showed that the percent of urban and agricultural land in the watersheds significantly affected both the water quality and the BMI of the streams. Specifically, a higher percent of urban land use had directly increased the biochemical oxygen demand (BOD) and total phosphorus (TP), and deteriorated the BMI of streams. Similarly, higher proportions of agricultural land use had also directly increased the BOD, total nitrogen (TN), and total phosphorus (TP) concentrations, and lowered the BMI of streams. In addition, it was observed that the percent of urban and agricultural land use had indirectly deteriorated the BMI through increased BOD. However, we were not able to observe any significant indirect effect of the percent of urban and agricultural land use through increased nutrients including TN and TP. These results indicate that increased urban and agricultural land use in the watersheds had directly and indirectly affected the physicochemical characteristics and benthic macroinvertebrate communities in streams. Our findings emphasize the need to develop more elaborate environmental management and restoration strategies to improve the water quality and biological status of streams.
Highlights
Land use affects the physical and chemical characteristics of streams, which significantly impacts water quality and fluvial ecosystems [1,2,3]
We aimed to develop a structural equation model (SEM) to assess the relationships between land use, water quality parameters, and benthic macroinvertebrates indexes in streams of the Nam-Han River watershed, South
The proportion of agricultural and urban land use in watersheds is a major determinant of biochemical oxygen demand (BOD), total nitrogen (TN), and total phosphorus (TP) in streams [18] and has been frequently linked to nutrient and heavy metal contamination from non-point pollution sources, such as pesticides and fertilizers [56,57]
Summary
Land use affects the physical and chemical characteristics of streams, which significantly impacts water quality and fluvial ecosystems [1,2,3]. Anthropogenic activities influence the type, intensity, and amount of land use within a watershed and have been closely associated with the amount of material and nutrients discharged into nearby streams. Res. Public Health 2020, 17, 2116; doi:10.3390/ijerph17062116 www.mdpi.com/journal/ijerph
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