Surface water quality and land use in Wisconsin, USA - a GIS approach

To explore effective water pollution mitigation, it is essential to study the complex relationship between surface water quality and land-use patterns in different regions under various spatial scales. A geographic information system (GIS) based approach together with statistical analysis was used to examine this complex relationship in the State of Wisconsin, USA. The data on watershed, land use/cover and water quality of 1988-1996 were collected and integrated from the Wisconsin Department of Natural Resources, the Wisconsin Initiative for State-wide Cooperation on Landscape Analysis and Data, and the US EPA, respectively. Nonparametric statistical analysis techniques were employed to analyse the relationship between land-use categories and surface water quality variables such as calcium, total phosphorus, lead and fecal coliform at the watershed level. Then a GIS-based spatial analysis was further conducted for variables that were significantly related to land use. The results showed that 14 out of 21 water quality variables were significantly and positively related to the urban and agricultural lands, and were significantly and negatively related to the forest and wetland land-use types. In addition, a strong positive rank correlation between electric conductivity related water quality variables and urban/agricultural land use was also observed. The results and the information extracted from this research would be useful to land-use planners and environmental management agencies for monitoring and reducing the water pollution.