Hydrologic Analysis and Restoration Considerations for the Upper Klamath Lake Sub-Basin, Klamath County Oregon

Aquatic ecosystems in the Upper Klamath Basin (Upper Basin), Oregon are degraded as a result of more than a century of land use alterations due to logging, dams, irrigated agriculture, and cattle grazing. These changes have led to degraded habitat conditions including decreased baseflow, loss of vegetation, increased stream temperature, fish impediments, and nutrient loading. All these factors negatively impact watershed function and resident fish populations, which have experienced severe declines in recent decades. The primary threats to fish populations include habitat loss, degraded water quality, barriers and entrainment, and predation and competition from non-native species. Millions of dollars have been spent since the late-1900’s to restore aquatic habitat in the Upper Basin primarily to improve the distribution and abundance of endangered and threatened fish species. This project details the hydrologic characteristics of three primary tributaries in the Upper Klamath Lake Sub-Basin including Sevenmile Creek, Wood River, and the Williamson River (including spring tributaries). Available discharge data was assembled to plot seasonal fluctuations in flows and identify annual peak flow at different re-occurrence intervals. Stream systems in the UKL Sub-Basin show a range of hydrologic inflow due to groundwater and/or snow-melt run-off. Characteristics of spring-fed vs. run-off dominated stream systems are reviewed and recommendations are made for how to address restoration practices considering the hydrologic and geomorphic characteristics of stream channels