Projects & Programs
Water Quality Modeling of Lake Simtustus, Oregon
Lake Simtustus is one of the three reservoirs that were created as part of Portland General Electric’s (PGE’s) Pelton Round Butte hydroelectric project near Madras, Oregon. Lake Simtustus was formed as a result of the construction of Pelton Dam on the Deschutes River. In conjunction with the re-licensing process, PGE has developed an adaptive management plan for re-establishing natural anadromous fish runs above Round Butte Dam upstream of Lake Simtustus. PGE is considering incorporation of a selective withdrawal operation at Round Butte Dam upstream of Lake Simtustus to improve fish passage at Round Butte Dam and comply with temperature criteria. However, selective withdrawal would release water with a different quality than that of present conditions.
PNNL staff developed a predictive temperature and water quality model of Lake Simtustus using the U.S. Army Corps of Engineers' (USACE's) CE-QUAL-W2 reservoir water quality model. Model results indicated that the selective withdrawal operation at Round Butte Dam improves dissolved oxygen (DO) and lowers the temperature of Lake Simtustus in summer. Chlorophyll-a and pH levels are slightly elevated during summer but are not a major concern considering the temperature and DO benefits provided by the selective withdrawal operation.
Project Highlights:
- A predictive temperature and water quality model was developed using USACE’s CE-QUAL-W2 reservoir water quality model
- The model successfully reproduced stratification and destratification processes, seasonal variations of temperature, algal production, and nutrient cycles
- Model results indicated improvement of DO and lowering of temperature using a selective withdrawal operation at Round Butte Dam.