Projects & Programs
TMDL/Watershed Model Development – Deschutes River, Oregon
The lower Deschutes River is listed on Oregon’s 303(d) water quality limited list for temperature, pH and dissolved oxygen (DO). PNNL staff used the Environmental Protection Agency's (EPA's) Better Assessment Science Integrating Point and Nonpoint Sources (BASINS) modeling system to develop a watershed and water quality model for the basin. Watershed models of mainstem tributaries were needed to support the development and application of a dynamic reservoir/river system model for the Pelton/Round Butte Hydroelectric Project on the mainstem of the lower Deschutes river. Of primary interest was the temperature and water quality (nutrients-algae-pH-DO) response of the reservoir/river system to proposed changes in project operation. Watershed models of hydrology and temperature were set up using BASINS and the Nonpoint Source Model (NPSM) interface. NPSM is the BASINS version of EPA’s Hydrologic Simulation Program-Fortran (HSPF) model.
NPSM models of the White River and Trout Creek watersheds provide continuous temperature and tributary data for input to a dynamic river model of the lower river (CE-QUAL-W2). A preliminary calibration of the watershed models to available historical temperature and flow data showed that the model predictions were reasonable and could be used as input for calibration of the dynamic lower Deschutes River water quality model.
The White River basin includes a portion of the 11,239-foot-high Mt. Hood, which is ice and snow covered throughout the year. A comparison of observed and modeled discharge at the mouth of the White River indicates that the seasonal accumulation of snow and snowmelt runoff is reproduced well by the watershed model of this basin.
Project Highlights:
- PNNL used the EPA BASINS modeling system to develop a watershed and water quality model for the basin
- The BASINS and NPSM modeling of White River and Trout Creek watersheds generated flow information in the absence of U.S. Geological Survey data
- NPSM data was used as input to CE-QUAL-W2 and RMA-1 models to dynamically simulate the water quality of the lower Deschutes River.