Endangered Species Act (ESA) compliance, ongoing water rights adjudication, and other litigation conflated by hydrologic uncertainty contribute to complex water management policy in the Klamath River basin. In addition, the upcoming removal of four hydroelectric dams on the Klamath River will require further policy changes. The Bureau of Reclamation (Reclamation), in coordination with other agencies, manages water resources in the Upper Klamath River basin to meet these complex challenges. RiverWare has emerged as an important modeling tool supporting that effort. In 2020, CADSWES and Reclamation developed the Klamath River Operations Model to support daily operations decisions for the Klamath Irrigation Project, as well as environmental and tribal needs. The model development team, including Reclamation and CADSWES, has since improved the operations model to incorporate long-term planning capability. Reclamation now has a single Klamath Planning and Operations Model (KPOM) that facilitates daily operations decisions as well as multiple year simulations to support long-term planning efforts, including future ESA consultations and vulnerability assessment.

Further, as part of a series of Department of Interior Klamath River Basin Science Initiatives, RiverWare is the backbone in a multi-faceted study to estimate what streamflow in the watershed might have been in the absence of major development over the past 150 years. RiverWare effectively integrates relevant process models to estimate natural streamflows through mass balance calculations. This unique application of RiverWare requires novel development of rules to account for changes in infrastructure, lake/reservoir capacities, channel connectivity, and groundwater/surface water interactions. These RiverWare tools taken together support Reclamation in addressing the numerous water management challenges in the Klamath River basin. This presentation provides highlights of these recent modeling efforts.