Zosel Dam Regulation Model

In 2018, the United States Army Corps of Engineers (USACE) developed a simple regulation model to estimate the levels of Osoyoos Lake based on inflow conditions and Zosel Dam operations. This initial effort was limited and identified several challenges to making the model relevant for real-time operations. These challenges included improving lake storage estimates and estimates of inflow and outflow from the dam. Dry conditions in the summer of 2024 presented challenges for the regulation of Zosel Dam. Improving USACE’s regulation model would give the International Osoyoos Lake Board of Control (IOLBC) a tool to better manage changing conditions.  

In 2026, the IOLBC launched a project to build upon USACE’s existing Zosel Dam model.  The project will simplify the model’s regulation tool, allow users to set future target outflows from Zosel Dam based on gate settings, and improve the model code.  The tool will be based on the following parameters: new gate flow curves from Northwest Hydraulic Consultants (NHC), the elevation of Osoyoos Lake, and downstream river elevation. This will allow Zosel Dam’s gate settings to be estimated for specific target flows.  

This new regulation model for Zosel Dam will improve shared scientific understanding in the Osoyoos Lake watershed by giving the IOLBC and the Dam’s operator (Washington State Department of Ecology) a clearer understanding of how Dam operations should change based on different conditions in the watershed. As the project will aid in joint decision making for Zosel Dam, it will function as a shared solution that will improve the resolution of water issues, which is crucial for transboundary watersheds. The new regulation model will also aid in communicating the effects of the operation of Zosel Dam to the public in the Osoyoos Lake watershed through visuals.