Implications of Climate Change for Okanagan Basin Water Availability and Salmonid Restoration Planning

The Okanagan fish-and-water management tool (Ok-FWMT) is a coupled-set of 4 biophysical models of key relationships among climate, fish and water that interact with a 5^th water-management rules model used to predict consequences of water management decisions for fish and other water users. Ok-FWMT software allows system users to explore water management decision impacts in: the current water-year (real-time mode), previous years (retrospective mode) or future years (prospective mode) given data on water supplies, climate and fish population state(s). Here we consider climate change impacts on future fish-and-water management options in the Okanagan Basin by examining projected water budgets, seasonal inflows and water management options for the 2050s within the context of established operating rules embedded within the Canada-BC Okanagan Basin Agreement and the Ok-FWMT.  If future water supply projections are correct, average egg-to-yearling survival for endangered Okanagan River sockeye could fall dramatically. Alarmingly, our simulated 2050s water availability conditions led to the complete loss of high-survival juvenile  cohorts, reducing the sockeye population’s resilience. In addition, our 2050 period fish/water managers were unable to achieve the current September 30 operating benchmark for Okanagan Lake even once in 28 simulated years. Consequences of extensive lake draw-downs could be catastrophic, highlighting the need for proactive intervention and adaptation. The solution includes much more strenuous surface and groundwater license restrictions and sensible, enforceable demand management regulations on all new and existing water extraction activities. Creation of water banks, water markets and water license buy-backs are also foreseeable. Politicians, planners and regulators should  move forward with  anticipatory water conservation and management steps now to avoid the creation of increasingly complex and insoluble problems later. Failure to do so will have dire consequences for aquatic ecosystems and the quality of life in the Okanagan. The multi-agency Okanagan water supply and demand study in Canada is an important first step to developing a sustainable water strategy to meet both human system and aquatic ecosystem needs in the face of future climate change.