A Spatial Model to Assess the Effects of Hydropower Operations on Columbia River Fall Chinook Salmon Spawning Habitat

Abstract

Priest Rapids Dam on the Columbia River produces large daily and hourly streamflow fluctuations throughout the Hanford Reach during the period when fall Chinook salmon Oncorhynchus tshawytscha are selecting spawning habitat, constructing redds, and actively engaged in spawning. Concern over the detrimental effects of these fluctuations prompted us to quantify the effects of variable flows on the amount and persistence of fall Chinook salmon spawning habitat in the Hanford Reach. Specifically, our goal was to develop a management tool capable of quantifying the effects of current and alternative hydrographs on predicted spawning habitat in a spatially explicit manner. Toward this goal, we modeled the water velocities and depths that fall Chinook salmon experienced during the 2004 spawning season, plus what they would probably have experienced under several alternative (i.e., synthetic) hydrographs, using both one‐ and two‐dimensional hydrodynamic models. To estimate spawning habitat under existing or alternative hydrographs, we used cell‐based modeling and logistic regression to construct and compare numerous spatial habitat models. We found that fall Chinook salmon were more likely to spawn at locations where velocities were persistently greater than 1 m/s and in areas where fluctuating water velocities were reduced. Simulations of alternative dam operations indicate that the quantity of spawning habitat is expected to increase as streamflow fluctuations are reduced during the spawning season. The spatial habitat models that we developed provide management agencies with a quantitative tool for predicting, in a spatially explicit manner, the effects of different flow regimes on fall Chinook salmon spawning habitat in the Hanford Reach. In addition to characterizing temporally varying habitat conditions, our research describes an analytical approach that could be applied in other highly variable aquatic systems.

Modelling Tools to Analyze and Assess the Ecological Impact of Hydropower Dams

“…Nevertheless, most model approaches base their assessment on physical-chemical water quality or the habitat suitability of adult fish (e.g., Ruetz and Jennings [32]; Freeman et al [31]; Cerny et al [62]; Grand et al [55]; Hatten et al [22]; Garcia et al [18]; Li et al [99]; Cioffi and Gallerano [112]; Chen et al [131]; Wang et al [25]), including often purely the most common and economic valuable species (e.g., trout, salmon) or endangered species. One publication considered the impact of flow regulation on algae [38]; one paper focused on the effect on habitat suitability of amphibians [26]; and just three papers considered macroinvertebrates [25,37,115] in their assessment.…”

“…Ecological models can support decision making in environmental and conservation management [16] and have already been applied to assess the impact of dams on fish [17][18][19][20][21][22], macroinvertebrates [23][24][25], amphibians [26] and vegetation [27][28][29]. Models are being increasingly used in environmental assessment, planning and management [30].…”

An Ecohydraulic Model to Identify and Monitor Moapa Dace Habitat

“…To insure confidence in the predictability of our 2-D-hydrodynamic model, we followed the methodology and steps in the on-line manual http://www.river2d.ualberta.ca and real-life applications [30], [31]. Refer to File S1 for details related to bathymetry, substrate, or water temperature; File S2 for hydrodynamic boundary conditions; and File S3 for a calibration chart of Plummer Creek (0.071 cms).…”

Complexity of bioindicator selection for ecological, human, and cultural health: Chinook salmon and red knot as case studies

“…The spawning areas need downward flow of water through the part of the nest where the eggs are located (eggs are about 20 cm below the surface, Hanrahan et al 2004). Salmon prefer nesting in areas with water velocities greater than 1 m/s and where stream flow fluctuations are reduced (Hatten et al 2009). Fine sediment impairs egg survival because enough water does not flow through to provide sufficient oxygen for developing embryos (Honea et al 2009).…”