Predicted total dissolved gas (TDG) in the Snake and Columbia rivers with daily observed data. TDG estimates are produced using the COMPASS model (CRiSP.1 model through 2006). The primary input to the dam-specific gas production equation is spill at the dam. Hydrosystem data is courtesy of Bonneville Power Administration (flow forecasts) and U.S. Army Corps of Engineers, NWD and Grant County PUD. See the Methods page for more information.