PNNL

Abstract

The U.S. Army Corps of Engineers has used simulation modeling to narrow its options for improving survival rates for juvenile salmonids migrating out of the Snake River. This model, called the Major System Improvements Analysis (MSIA) model, was developed for this particular application by Battelle–Pacific Northwest Division in Richland, Washington, and its subcontractor, Decision Support in Richland, WA. The model uses OptQuest optimization software from Decisioneering Inc. in Denver, Colo., to simulate many combinations of options and identify the best performers. Downstream-migrating juvenile salmonids encounter eight hydro projects on the Snake and Lower Columbia rivers. Five of these are under the direction of the Walla Walla District of the Corps. Four of these five projects feature the capability to transport, by barge or truck, fish collected in their juvenile bypass systems. Fisheries managers must identify ways to operate and configure the dams and fish transportation systems to meet or exceed the survival rates set forth in the Biological Opinion issued by the National Marine Fisheries Service in 2000, says Kenneth D. Ham, senior research scientist at Pacific Northwest National Laboratory, which is operated by Battelle. The challenge was to determine whether a candidate operation or construction option provided the expected survival benefits when the operations and configurations of the entire system were considered, Ham says. For example, upstream transportation alternatives have a potential to influence the number of fish exposed to alternatives at downstream dams. Potential project enhancements to survival that were available for evaluation using MSIA included divider walls, spillway improvements, new outfall locations, turbine improvements, new or modified fish facilities, extended screens, and new barges. The model was designed to screen various combinations and identify the subset that met minimum criteria. In fact, all combinations of construction items at the five projects amount to about 17 million. When combined with the 18,000 operational combinations and considering species and route flows, the total number of combinations could easily exceed 3 quadrillion, Ham says. Acceptable combinations exhibited a range of survival values, construction costs, and power revenues. Overall, only several hundred combinations met the minimum survival criteria. From these sets of acceptable performers, top performers were identified that had the highest survival performance for each level of revenue. All combinations selected as top performers provided higher survivals and greater net revenue than the operations specified in the biological opinion, Ham says. This simulation modeling approach provided a set of cost-effective combinations from which a mix of survival benefits, construction costs, and power revenues could be chosen to meet stewardship goals. However, a new Biological Opinion in 2008 included dam survival “Performance Standards” for juvenile salmon at each dam changing the biological criteria used in the MSIA study.