| Application of simulation models to assess the fate, transport, and effects of constituents is useful for examining aquatic system responses to multiple stresses and predicting undesirable outcomes. A set of numerical models is applied to a reservoir-river system on the Klamath River, California, to investigate remedial measures for salmon restoration and protection. The existing one-dimensional water quantity and quality model Water Quality for Reservoir River Systems (WQRRS) is applied for reservoir simulation, and the hydrodynamic model RMA-2 and water quality model RMA-11 are applied in one-dimensional form for river simulation. RMA-11 was modified to include an attached algae component to represent primary production in the river environment.; The models were calibrated and validated using field observations from the Klamath River, California, where chinook salmon, coho salmon, and steelhead stocks have declined considerably due, in part, to elevated water temperature, depressed dissolved oxygen concentrations, and nutrient loading from upstream sources. A new method of calibrating the stream models for flow and water temperature is presented. Using sub-daily temperature observations, the hydrodynamic and water quality models are applied in tandem, reproducing the diurnal temperature trace at multiple downstream locations.; Sub-daily water quality modeling poses challenges and opportunities for water quality management. Simulation periods up to six months in length, at one-hour time steps, provide seasonal, as well as diurnal water quality response throughout the reservoir-river system. A water quality index is developed to assess ecosystem health in light of temperature and dissolved oxygen requirements for various life-stages of anadromous fish. The individual indices are designed to utilize sub-daily field observations or simulated values. Further, the dissolved oxygen and temperature indices may be interpreted individually, or aggregated to assess potential combined stresses of interacting parameters.; Seasonal variations in flow, meteorology, and existing and potential alternative management operations were evaluated for both the reservoir and river systems. Alternative management scenarios include varying flow, relocating reservoir penstock intake elevations, selective reservoir withdrawal, and increased and decreased reservoir storage. Simulation results are used to calculate water quality indices for temperature and dissolved oxygen, and a combined index was applied to assess aquatic habitat suitability for salmon. |
