Fish and Water Management in the Okanagan lakes

November 8, 2006

For most of us, fluctuating Okanagan Lake levels aren’t a matter of life and death. If the lake is high, we worry about flooding, and if it is low, boats can run aground or water intakes may start pumping air. But it is a different story for kokanee salmon and their cousins the sockeye, which live downstream in the Okanagan River and Osoyoos Lake. Because many of the kokanee spawn along the lakeshore and all the sockeye spawn in the Okanagan River, lake levels can determine whether salmon eggs and young will live or die.

The Okanagan sockeye population first began to decline in the early 1900s as a result of changes to the environment, and this decline continues.  As recently as the 1970s, the Okanagan Lake kokanee population was over 1-million, half of these spawning along the shore, and half spawning in creeks that drain into the lake.  Many factors contributed to their dramatic crash in the 1980s and ‘90s, and by 1998 the number of lake-spawners dropped to less than 10,000 – leading to the collapse of a million-dollar sports fishery. Now a unique partnership and the latest in computer technology are changing the odds for kokanee and sockeye survival and the recovery of the fishery.

Okanagan Lake is controlled by a dam in Penticton. Engineers try to keep lake levels within a range that gives flood protection, but ensures water is available for domestic use and agricultural irrigation, boat navigation, and kokanee survival. It is a delicate balance. In the fall, the lake must be drawn down low enough that the kokanee don’t spawn too high on the shoreline. Winter rains fill the lake again, and water managers have to release enough water to make room for spring snowmelt. Releases from Okanagan Lake also control flows in the Okanagan River – affecting the survival of sockeye salmon eggs and young downstream. Releasing too little water can expose and kill the eggs, but releasing too much water too fast can scour the eggs from the gravel before they have a chance to develop.

In 2001, a group called the Canadian Okanagan Basin Technical Working Group (COBTWG) became convinced that by incorporating new technology and biology into lake management they could dramatically improve salmon survival without increasing flood risk or economic impacts. This group represents a partnership between Fisheries and Oceans Canada, the BC Ministry of Environment and the Okanagan Nation Alliance. Together, they developed a computer model – the Fish-Water Management Tool – that uses real-time information about spawning patterns, water temperature, lake levels, and weather conditions to help water and fisheries managers in making the optimum water release decisions to balance all water management priorities. Researchers estimate that this tool has the power to increase sockeye survival in Okanagan River by up to 55%, and it has been valuable for training new water managers.  Now in full use, this tool has been acclaimed as a great success, and other areas are working to follow the Okanagan’s example. The Fish-Water Management Tool is a great example of how partnerships and the appropriate use of new technology can make real improvements in how we steward water resources.