Water temperature and total dissolved gas (TDG) in the Columbia River is strongly influenced by the storage and release of water from projects like Grand Coulee Dam. Previous work has produced a temperature model (CE-QUAL-W2) of Lake Roosevelt for the purpose of informing in-season watershed management decisions to reduce take and to allow the evaluation of various operational and structural alternatives that can influence the regulation of water flow and temperature. The purpose of this project is to update the aforementioned Lake Roosevelt CE-QUAL-W2 model to also simulate TDG. This data may then be used as input to downstream Columbia River System water quality models. This capability is to assist in real-time decision making, and investigate alternatives to reduce total mass loading of TDG at Bonneville Dam while maintaining juvenile survival performance.