The South Santiam watershed covers approximately 1,270 square miles in western Oregon. Its hydrology is primarily influenced by snowmelt from the Cascade Range, which provides a significant source of surface water for the watershed. The snowpack in this region has been decreasing over time, contributing to a decrease in spring and summer streamflow. The watershed is home to several reservoirs, including Foster and Green Peter, which serve as important sources of water for the region. The reservoirs have experienced increased levels of harmful algae blooms in recent years, which can impact water quality and recreational use. The watershed also experiences a Mediterranean climate with wet winters and dry summers. Climate change is expected to continue to impact the region, with potential increases in temperature and changes in precipitation patterns.