Linking Nutrient Sources to Extreme Dissolved Oxygen, Ammonia Toxicity, Algae and Ph Impairments for an Impounded Reach Using A Hydro-dynamic Water Quality Model

Severe and persistent anoxia, ammonia toxicity, excess algae and elevated pH of an impounded reach of the upper Klamath River, Oregon are linked to pollutant sources using the water quality model CE-QUAL-W2. Typically, dissolved oxygen (DO) concentrations in the Keno Reservoir are less than 1.0 mg/L for a period of time between June and September which is less than Oregon's minimum DO criteria of 4.0 mg/L. Concurrent with the low DO period are elevated ammonia concentrations which cause violations of Oregon's acute and chronic toxic criteria and pH values greater than 9.0. Chlorophyll a concentrations also exceed the 0.015 mg/L criteria. The above water quality impairments are included on Oregon's 2004 / 2006 303(d) list. The water quality model CE-QUAL-W2 was used to quantitatively link the pollutant sources and the water quality response. Organic matter loading is dominated by the nonpoint source load from Upper Klamath Lake and leads to the DO and ammonia toxicity impairments. However, at times, the irrigation project (Klamath Project) can also contribute to severe water quality impairment. Currently, there is no measurable impact on DO concentration from loading by the point sources. The 2002 Upper Klamath Lake TMDL predicts restoration will shift the lake from a hyper-eutrophic to eutrophic state. Even under restored conditions, Upper Klamath Lake is predicted to deliver large nutrient loading to Klamath River in one out of every four years due to periodic naturally occurring algae blooms.