McKenzie River Geology

Water resource management is rapidly becoming an important issue throughout the Pacific Northwest. Increasing and often competing demands for water for agricultural, urban and aquatic habitat requirements, highlight the critical importance of understanding flow regimes and their sensitivity to climate and land use change. This study focuses on the McKenzie River, a major tributary of the Willamette River.

In the McKenzie watershed, the source of most of the available water is the Cascade Mountains, which include two distinct geologic provinces: the High and Western Cascades. Preliminary analysis of High and Western Cascades in terms of seasonal- and event-based hydrographs suggests that these are dramatically different systems. Consequently, during the summer, the High Cascade systems contribute disproportionately to the maintenance of discharge volumes and stream temperature. Our analysis suggests that most of the water in the High Cascade systems comes from spring fed rather than shallow sub-surface flow. The dynamics of these springs, however, have not been well studied.

In this research, we undertake a comprehensive study of High Cascade spring systems using a combination of field data collection, empirical analysis and process based modeling. We are investigating the timing and source of water for several springs within the McKenzie and developing a mechanistic understanding of differences between spring and shallow subsurface water dominated catchments and their sensitivity to climate and land use change. Results from this project will contribute to our understanding of High Cascade spring systems and highlight implications for water resource management in this region.