Spatial and temporal relationships between water quality and land use in northern Georgia, USA

The impact of land use changes caused by urban sprawl on water quality since the 1970s in northern Georgia, USA is studied by examining the spatial and temporal relationships between land use and water quality indicators in 43 watersheds through geographic information system (GIS) and statistical analyses. GIS analyses are used to delineate watersheds using Digital Elevation Models for water sampling sites and to derive land use indicators such as urban land, forest, agricultural land, and wetland for each watershed. Statistical analyses are used to examine, quantify, and compare the relationships between water quality and land use indicators and to find good predictors of water quality changes in response to the spatial and temporal variations of land uses. Significant spatial relationships are found between all the 14 studied water quality indicators, including dissolved oxygen, specific conductance, dissolved nutrients, dissolved ions, dissolved solids, and suspended sediment, and two land use indicators (percentages of urban land and forest). The more urbanized watersheds with higher percentage of urban land and lower percentage of forest tend to have higher concentrations of water pollutants. However, no significant temporal relationships are found between water quality and land use indicators. To fully evaluate, explain, and predict water quality long-term change, it is necessary to consider more natural and anthropogenic factors, such as water pollution control technology, policy, and climate change.