American Society of Civil Engineers


Temperature Stratification and Water Quality Modeling for Lake Simtustus, Oregon


by Zhaoqing Yang, (Senior Water Resources Engineer, Foster Wheeler Environmental Corporation, 12100 NE 195th Street, Suite 200, Bothell, WA 98011), Tarang Khangaonkar, (Senior Consulting Engineer, Foster Wheeler Environmental Corporation, 12100 NE 195th Street, Suite 200, Bothell, WA 98011), Curtis DeGasperi, (Water Quality Engineer, King County Wastewater Treatment Division, Department of Natural Resources, 201 South Jackson Street MS KSC-NR-0503, Seattle, WA 98104), Steve Breithaupt, (Senior Water Resources Engineer, Foster Wheeler Environmental Corporation, 12100 NE 195th Street, Suite 200, Bothell, WA 98011), and Kevin Marshall, (Project Manager, Portland General Electric, 121 SW Salmon Street, Portland, OR 97204)

pp. 765-782, (doi:  http://dx.doi.org/10.1061/40628(268)49)

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Document type: Conference Proceeding Paper
Part of: Estuarine and Coastal Modeling (2001)
Abstract: Lake Simtustus, impounded by the Pelton Dam, is the second of three reservoirs that are a part of Portland General Electric’s (PGE’s) Pelton/Round Butte Hydroelectric Project, located on the Deschutes River in central Oregon. Lake Simtustus is a narrow, deep lake with a flow field that is strongly affected by daily peaking inflows, outflows, and thermal stratification. This paper describes the development of a water quality model of Lake Simtustus to support PGE’s proposed modifications to project operations for enhancement offish passage. A dynamic, laterally averaged, vertical, 2-D water quality model for Lake Simtustus was developed using the CE-QUAL-W2 model to predict water quality under existing project conditions and to evaluate the impacts on water quality that would result from the proposed modifications to project operations. Model calibration was complicated by the fact that Lake Simtustus exhibits sharp density destratification in the fall and has two pronounced algal growth seasons (spring and fall blooms) that are dominated by a different algal species. The water quality in the hypolimnion is dominated by the cooler inflows while the water quality in the epilimnion is dominated by meteorological forcing and in-lake phytoplankton kinetics. The model was successfully calibrated and validated using year-long data sets from 1995 and 1996. Model results showed good agreement with the observed data, reproducing the lake stratification and destratification processes and the eutrophication cycle very well. The model was used to demonstrate that the proposed operational modifications would improve in-lake and downstream water quality.


ASCE Subject Headings:
Water temperature
Water quality
Oregon
Lakes
Stratification