An Estimated Structural Equation Model to Assess the Effects of Land Use on Water Quality and Benthic Macroinvertebrates in Streams of the Nam-Han River System, South Korea

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.

Spatiotemporal variation of nitrogen and phosphorus and its main influencing factors in Huangshui River basin

“…Meanwhile, the land use type of this catchment was mainly grassland and woodland (>0.85), and the impervious ground area only accounted for a small proportion (<0.01). This is in accord with that agriculture land and urban land were negatively correlated with surface water quality, whereas forested land, water area, and grassland were positively correlated with water quality (Chen et al, 2016;Lee et al, 2020;Xu et al, 2019a). The PPI was relatively high (>0.09), and the secondary industry was underdeveloped (PSI was approximately equal 0.37).…”

Regression Tree Analysis for Stream Biological Indicators Considering Spatial Autocorrelation

“…Urbanized areas, including cultivation areas in the Nam-Han River Basin are concentrated downstream, and cover approximately 24% of the total area. Furthermore, forests cover approximately 70% of the total area of the basin [ 61 ].…”

Eutrophication and the Ecological Health Risk

“…Lee et al [ 25 ] evaluated the mechanistic pathways between land use and the deterioration of both stream water quality and biological assemblages using a structural equation model (SEM), reflecting the impact of agricultural and urban land use on water quality and the benthic macroinvertebrate index (BMI) in river systems. The estimates from the SEM showed that an increase in both urban and agricultural land use percentage directly increased the biochemical oxygen demand (BOD) and TP while decreasing the BMI of streams.…”

“…Herein, I summarize the contributed papers in the context of eutrophication and related risks to the health of ecological systems to paint an overall picture of this Special Issue ( Table 1 ). Three studies focused on “eutrophication” [ 17 , 18 , 19 ], four on “ecological health risk” [ 20 , 21 , 22 , 23 ], and a further three papers on “ecosystem health and services” [ 24 , 25 , 26 ] have been included in this issue. A more detailed summary of all articles is offered in the following section.…”