Developing the Historical Context for Understanding Present Day Land Use-Water Quality Relationships

Abstract

Historic land use is a potentially significant factor determining present day water quality and stream integrity. Studies have shown that past land uses such as the extent and intensity of agriculture within a basin can have lasting effects on water quality and may possibly be more important to present day water quality than current land-cover conditions (Harding et al 1998). However, these relationships are poorly understood (Allen et al 2004). In this study we developed a long term history of land use within ten study catchments in rural King County. This study is one component of a larger project to monitor the effectiveness of the Critical Areas Ordinance in projecting water quality in rural King County. The purpose of the historic assessment is two-fold: first, to determine if historic land use can help explain variation in the present conditions of the watersheds and second, to inform our understanding of the trajectory of water quality changes in these basins.