Abstract

During 2005, the U.S. Geological Survey (USGS) developed, calibrated, and validated a multidimensional flow model for simulating streamflow in the white sturgeon spawning habitat of the Kootenai River in Idaho. The model was developed as a tool to aid understanding of the physical factors affecting quality and quantity of spawning and rearing habitat used by the endangered white sturgeon (Acipenser transmontanus) and for assessing the feasibility of various habitat-enhancement scenarios to re-establish recruitment of white sturgeon. At the request of the Kootenai Tribe of Idaho, the USGS extended the two-dimensional flow model developed in 2005 into a braided reach upstream of the current white sturgeon spawning reach. Many scientists consider the braided reach a suitable substrate with adequate streamflow velocities for re-establishing recruitment of white sturgeon. The 2005 model was extended upstream to help assess the feasibility of various strategies to encourage white sturgeon to spawn in the reach. At the request of the Idaho Department of Fish and Game, the USGS also extended the two-dimensional flow model several kilometers downstream of the white sturgeon spawning reach. This modified model can quantify the physical characteristics of a reach that white sturgeon pass through as they swim upstream from Kootenay Lake to the spawning reach. The USGS Multi-Dimensional Surface-Water Modeling System was used for the 2005 modeling effort and for this subsequent modeling effort. This report describes the model applications and limitations, presents the results of a few simple simulations, and demonstrates how the model can be used to link physical characteristics of streamflow to the location of white sturgeon spawning events during 1994–2001. Model simulations also were used to report on the length and percentage of longitudinal profiles that met the minimum criteria during May and June 2006 and 2007 as stipulated in the U.S. Fish and Wildlife Biological Opinion.