Physical Habitat Comparison of White sturgeon Populations in the Columbia Basin with Consistent, Intermitant, and Negligible Spawning Success Based on Morphological Analysis and Hydrodynamic Models

White sturgeon populations are isolated by reach throughout most of the Columbia River Basin because of dams and other factors. Currently, these populations exhibit a wide range of spawning success.  We studied channel morphology and used spatially explicit hydrodynamic models to characterize and compare the physical environment available to the sturgeon in a reach that exhibits consistent (below Bonneville Dam in the Skamania reach), inconsistent (below McNary Dam in the John Day Pool reach), and negligible spawning success (Kootenai River meander-straight reach in Northern Idaho). The Kootenai white sturgeon has been listed as endangered since 1996. Identifying differences in physical habitat for 5, 50, and 90 percent flow exceedance amongst these reaches provide information that resource managers can use to alter the habitat in reaches with negligible spawning success to a more desirable state. Habitat comparisons of the three reaches show the Skamania reach has the greatest amount of side channel habitat, greatest variability in width-depth ratio, steepest and most variable water slope, highest and most variable streamflow velocity, highest bed shear stress and sediment mobility, and most notably the greatest flow complexity. Flow complexity was characterized as the ratio of recirculation area and reach area, the Skamania reach has an order-of-magnitude greater ratio than the other two study reaches. The Kootenai reach has the most sinuous channel and uniformly distributed pools, however has the lowest streamflow velocity, bed shear stress and sediment mobility. Percentage of the Skamania and John Day Pool reach with a gravel-cobble riverbed is about 61 and 88 percent, much greater than 11 percent in the Kootenai reach. The Kootenai reach is dominated by a mobile sand bed.