Gas Saturation and Sensitivity Analysis Using CRiSP

Introduction The Army Corps of Engineers began the Gas Abatement Study in order to address the problem of gas and its effects on the Snake and Columbia Rivers. One important question is how much gas reductions caused by structural changes at a few or several of the dams would benefit fish survival. A gas sensitivity analysis was done using CRiSP to see how sensitive this model is to changes in gas levels and to get a preliminary idea of the effects of reducing gas at the region’s top gas producing dams. In this analysis, steelhead and yearling chinook were released above Lower Granite pool and followed through the tailrace of Bonneville Dam. The runs were done under two scenarios: 1) spill caps aimed at keeping the gas below 120-125% were set for the Snake and lower Columbia River dams and 2) spill fractions were set to meet an 80% FPE at each dam with no set spill caps.