title: Impacts of land use and population density on seasonal surface water quality using a modified geographically weighted regression.
abstract: As an important regulator of pollutants in overland flow and interflow, land use has become an essential research component for determining the relationships between surface water quality and pollution sources. This study investigated the use of ordinary least squares (OLS) and geographically weighted regression (GWR) models to identify the impact of land use and population density on surface water quality in the Wen-Rui Tang River watershed of eastern China. A manual variable excluding-selecting method was explored to resolve multicollinearity issues. Standard regression coefficient analysis coupled with cluster analysis was introduced to determine which variable had the greatest influence on water quality. Results showed that: (1) Impact of land use on water quality varied with spatial and seasonal scales. Both positive and negative effects for certain land-use indicators were found in different subcatchments. (2) Urban land was the dominant factor influencing N, P and chemical oxygen demand (COD) in highly urbanized regions, but the relationship was weak as the pollutants were mainly from point sources. Agricultural land was the primary factor influencing N and P in suburban and rural areas; the relationship was strong as the pollutants were mainly from agricultural surface runoff. Subcatchments located in suburban areas were identified with urban land as the primary influencing factor during the wet season while agricultural land was identified as a more prevalent influencing factor during the dry season. (3) Adjusted R2values in OLS models using the manual variable excluding-selecting method averaged 14.3% higher than using stepwise multiple linear regressions. However, the corresponding GWR models had adjusted R2~59.2% higher than the optimal OLS models, confirming that GWR models demonstrated better prediction accuracy. Based on our findings, water resource protection policies should consider site-specific land-use conditions within each watershed to optimize mitigation strategies for contrasting land-use characteristics and seasonal variations.
authors.affiliation: Zhejiang Provincial Key Laboratory of Watershed Sciences and Health, Southern Zhejiang Water Research Institute (iWATER), Wenzhou Medical University, China.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Chen
authors.affiliation: Zhejiang Provincial Key Laboratory of Watershed Sciences and Health, Southern Zhejiang Water Research Institute (iWATER), Wenzhou Medical University, China.
authors.forename: Kun
authors.initials: K
authors.lastname: Mei
authors.affiliation: Zhejiang Provincial Key Laboratory of Watershed Sciences and Health, Southern Zhejiang Water Research Institute (iWATER), Wenzhou Medical University, China; Department of Land, Air and Water Resources, University of California, Davis, USA.
authors.forename: Randy A
authors.initials: RA
authors.lastname: Dahlgren
authors.affiliation: Zhejiang Provincial Key Laboratory of Watershed Sciences and Health, Southern Zhejiang Water Research Institute (iWATER), Wenzhou Medical University, China.
authors.forename: Ting
authors.initials: T
authors.lastname: Wang
authors.affiliation: Zhejiang Provincial Key Laboratory of Watershed Sciences and Health, Southern Zhejiang Water Research Institute (iWATER), Wenzhou Medical University, China.
authors.forename: Jian
authors.initials: J
authors.lastname: Gong
authors.affiliation: Zhejiang Provincial Key Laboratory of Watershed Sciences and Health, Southern Zhejiang Water Research Institute (iWATER), Wenzhou Medical University, China; Department of Land, Air and Water Resources, University of California, Davis, USA. Electronic address: mhzhang@ucdavis.edu.
authors.forename: Minghua
authors.initials: M
authors.lastname: Zhang
mesh_terms: D002681:China; D004784:Environmental Monitoring / Q000379:methods*; D005843:Geography; D006801:Humans; D008962:Models, Theoretical; D011156:Population Density; D012044:Regression Analysis; D045483:Rivers / Q000737:chemistry*; D012621:Seasons; D014874:Water Pollutants, Chemical / Q000032:analysis*; D060753:Water Quality
chemical_list: D014874:Water Pollutants, Chemical
keywords: GWR; Multicollinearity; OLS; Water pollution; Wen-Rui Tang River