HR: 09:00h
AN: H31H-04    [Abstracts]
TI: Optimizing Numerical Modeling and Field Data Collection in an Interdisciplinary Study of Upper Klamath Lake, Oregon
AU: * Cheng, R T
EM: rtcheng@usgs.gov
AF: U. S. Geological Survey, 345 Middlefield Road, MS-496, Menlo Park, CA 94025 United States
AU: Wood, T M
EM: tmwood@usgs.gov
AF: U. S. Geological Survey, 10615 S.E. Cherry Blossom Dr., Portland, OR 97216 United States
AU: Gartner, J W
EM: jgartner@usgs.gov
AF: U. S. Geological Survey, 520 N. Park Ave, Tucson, AZ 85719 United States
AB: Severe water quality conditions in Upper Klamath Lake (UKL), Oregon have led to critical fishery concerns for the region including the listing of Lost River and shortnose suckers as endangered species in 1988. Upper Klamath Lake was historically eutrophic but has become hypereutrophic, in large part due to land-use practices in the Klamath Basin. In 2002, in cooperation with the US Bureau of Reclamation (BOR), the U. S. Geological Survey (USGS) began a three-year study of the behavioral response of radio-tagged Lost River and shortnose suckers to water quality conditions in the lake. To support the tracking study, an array of continuous water quality monitors was installed in the northern third of UKL, and wind speed and direction were recorded at two sites. Two Acoustic Doppler Current Profilers (ADCPs) were deployed in the lake for two summer months in 2003 and 2004, providing the first continuous measurements of water velocities. Hydrodynamics is the key factor determining the water quality in the lake, velocities measured at only two locations are not sufficient to even qualitatively describe the lake-wide circulation. To establish a quantitative description of the complex circulation in UKL, an unstructured grid 3-D hydrodynamic model (UnTRIM) was implemented. When the observed wind speed and direction were used to drive the model, the numerical model reproduced the wind 'set-up' and 'set-down' at down wind and upwind ends of the lake, respectively. The UnTRIM model also reproduced the measured velocity time-series throughout the two-month ADCP deployment in 2003 with good agreement at a deep station. The correlations between the model results and ADCP data showed the same trend (slope nearly 1), but the R2 value was less than 0.5. This discrepancy is likely due to the fact that a uniform hourly averaged wind was applied over the lake. The complicated circulation patterns derived from the numerical model suggested a new strategy in designing the data collection network for the summer 2005 field season. Up to five wind anemometers have been installed around the lake to define the spatial variability of the wind field, and five ADCPs have been deployed in the lake to capture essential circulation features. The water quality monitoring network has been extended to cover the entire UKL, and monitoring stations have been placed at locations that will optimize the observation of important temporal and spatial variability in water quality as indicated by the circulation patterns predicted by the numerical model. The 2005 field data set will be used to refine the numerical hydrodynamic model upon which water quality modeling modules will be built. This case study demonstrated the use of field data to support numerical model implementation, and then the use of the numerical model results to improve the next cycle of field data collection. This loop optimizes the implementation of the numerical model and the effectiveness of field data collection.
DE: 0545 Modeling (4255)
DE: 1846 Model calibration (3333)
DE: 1847 Modeling
DE: 1871 Surface water quality
DE: 1894 Instruments and techniques: modeling
SC: Hydrology [H]
MN: Fall Meeting 2005