The Klamath Natural Flow Study seeks to understand what daily streamflow at twelve locations throughout the Klamath River Basin in Southern Oregon and Northern California might have been under 1981-2020 climate conditions in the absence of major development over the past 150 years. In the previous episodes (aired August 2023 and February 2025), the Reclamation team presented an overview of the study and highlighted some of the roadblocks in RiverWare model development. RiverWare is being used to integrate various process models to estimate natural streamflow. Roadblocks in RiverWare modeling presented in 2025 included:

• representing dynamic reservoirs,
• solving with variable reach routing parameters, and
• representing marshes and missing gage records.

This latest episode briefly recaps the study overview before focusing on the resolution of each of these roadblocks and progress made towards a final RiverWare modeling framework for the Klamath Natural Flow Study. In particular, progress focuses on implementing script-supported multiple run management (MRM) in RiverWare to replace previous script-driven model runs and developing a RiverSMART study for quantifying uncertainty in natural streamflow estimates. The script-supported MRM facilitates a two-step simulation, with each step requiring pre- and post-processing. In the first simulation step, the model solves upstream and represents 1981-2020 conditions. In the second step, the model solves downstream and represents pre-development conditions, with the output of the second step being estimated natural streamflow.