Lake Ozette Watershed Hydrologic Investigations

This proposed research will build upon hydrologic research projects conducted with PCSR funding during FY01 (Phase 1) and FY02 (Phase2).


Phase 1 of the project (FY01) developed a hydraulic model of the Ozette River to determine the backwater effects of large wood debris on lake level and the influence of historic wood removal on lake levels. Results found that wood removal affected summer lake levels by as much as one (1) meter, which could significantly affect sockeye spawning habitat availability and quality around the lake. Phase 2 of the project (FY 02) developed a hydrologic water budget of the lake (i.e., inputs, outputs and storage) that incorporated an improved hydraulic model of the Ozette River, water quantity (stream flow) data from tributaries and the lake outlet through a newly installed stream gage network, enhanced lake level data from a lake stage gage, enhanced lake shoreline bathymetry from LiDAR laser altimetry surveys, and meteorological data from a new weather station. A combined hydraulic and hydrologic water budget model for Lake Ozette is currently in the construction phase and will identify relative hydrologic processes within the lake. These processes (i.e., drivers of the lake level regime) will then be compared to historical data series (air photos) to identify potential causes of impairment to Sockeye spawning beach habitat and identify potential restoration solutions.


The current proposal (FY03 Phase 3) consists of two tasks: 1) continuing the basic data collection needed to support the Lake Ozette water budget model; and 2) developing the initial phases of a detailed distributed watershed model of hydrologic runoff processes of tributaries to Lake Ozette.


Tasks:
1.Basic Data Collection:

Currently installed stream gages (i.e., Big River, Umbrella, Crooked, Coal Creeks, Ozette River, Lake Ozette Stage) will continue to be developed and maintained to produce the entire data set needed for proper Lake Ozette water budget development. Basic rating curves will be complete by the end of summer 2004.
2.Distributed Watershed Hydrologic Modeling:

Current stream flow data and hypotheses on physical processes indicate that historical and current road building and timber harvest could have significantly altered catchment water production, increased peak stream flows, reduced stream base flows, and significantly affected the level regime of Lake Ozette (e.g., Bosch and Hewlett 1982; Jones and Grant 1996; Lewis et al. 2001; Bowling et al. 2002). Due to a lack of any historical stream flow data in these streams, a detailed distributed watershed hydrology model will be constructed to simulate runoff regimes and processes from lake tributaries under various historic land use scenarios.


State of the art distributed watershed models now exist such as DHSVM, the Distributed Hydrology Soil Vegetation Model (Wigmosta et al. 1994; Wigmosta et al. 2002). Distributed watershed hydrology models can explicitly represent the effects of topography, roads, and vegetation on water fluxes through the landscape. They can accurately model runoff output under different land use scenarios such as old-growth with no roads, second-growth and partially roaded, differential timber ages and fully roaded, and differential timber ages and improved road systems (Storck et al. 1998; Storck et al. 1999; Bowling and Lettenmaier, 2001; Lamarche and Lettenmaier 2001; Wigmosta and Perkins 2001; Bowling et al. 2002). Current stream flow data from Lake Ozette tributaries (i.e., Big River, Umbrella, Crooked, Coal Creeks, Ozette River, Lake Ozette Stage) would be used to calibrate the distributed watershed model.


Once developed, the modeled hydrology of the lakes tributaries will serve as a historic baseline comparison to current hydrologic conditions. In addition, once combined with completed modeling efforts of historic conditions of the lake outlet (Ozette River)

1)Increase the scientific understanding of hydrological processes in the Lake Ozette watershed.

2)Clearly identify limiting factors to healthy salmon production in the lake.

3)Identify watershed scale restoration strategies and priorities in the lake and basin.