Water Stewardship Information Sources
| ID | 1666 |
|---|---|
| Citation | Summit Environmental Consultants Inc. 2011. Osoyoos Lake Pland of Study - Study 6: Climate Change and its implications for managing lake levels in Osoyoos Lake. Prepared for the International Joint Commission. |
| Organization | International Joint Commission |
| URL | http://ijc.org/rel/boards/osoyoos/IJC%20Study%206%20FINAL%2020110414.pdf |
| Abstract/Description or Keywords | Water levels on Osoyoos Lake are managed according to Orders of Approval issued by the International Joint Commission (IJC). This study (Study 6) is one of several being conducted prior to the expiry of the current Orders in 2013. Its objective is to determine how robust the current Orders are in the face of past and future climate and hydrologic changes that affect Osoyoos Lake, and whether the Orders need to be amended to reflect these potential changes. The study included assembling literature on past and future climate and hydrologic changes in the Okanagan and Similkameen River Basins, contacting researchers to obtain up-to-date research findings, and using this knowledge in an examination of the current Orders of Approval. The level of Osoyoos Lake is continually managed to meet specified operating ranges in winter (November 1 to March 31) and summer (April 1 to October 31). The summer operating range depends on whether forecasts of spring inflows made by Canadian and U.S. forecasters exceed three thresholds. If any one of the three thresholds is not expected to be achieved, the lake operates in ﾓdroughtﾔ mode in the summer, which means that it can be filled and maintained at a level of up to 913.0 feet (and down to 910.5 feet) between April 1 and October 31. Otherwise, the summer lake level is maintained between 911.0 and 911.5 feet. Although historical trends in climate and streamflow can be confounded by other signals, such as those of the Pacific Decadal Oscillation (PDO) and the El Nino Southern Oscillation (ENSO) cycle, recent largescale trends relevant to the management of Osoyoos Lake are generally similar to present-day predictions of future changes. The future management of Osoyoos Lake will likely have to contend with a suite of gradually changing conditions, including: x Earlier spring runoff, which may necessitate changes to decision dates (i.e. when drought conditions are declared) and the dates of summer and winter operating ranges. x Reduced snowpack and lower spring runoff, which may have a direct bearing on the total water supply in summer. x Increased winter precipitation and warmer temperatures may cause more rain and less snow resulting in increased winter runoff. This additional water may help mitigate the lower spring runoff, but only if storage is available and utilized. If winter runoff were stored, summer lake levels could possibly be reached earlier. x Projected higher water demand and higher evaporation from Osoyoos Lake will further increase the pressure on the reduced water supply. x Potentially less accurate streamflow forecasts. Although historical data suggests the hydrology associated with the three criteria used to declare a drought has not significantly changed since the Orders were drafted in 1982, projections of reduced April 1 - July 31 Similkameen River runoff and Okanagan Lake inflow suggest that the current criteria may trigger droughts with increasing frequency in the future. Future management of Osoyoos Lake will need to adapt to the projected advance in the annual hydrograph, both for Similkameen River and Okanagan River. Given the limited storage represented by Osoyoos Lake, and the projected reduction in supply and increase in demand, the risk of water deficits will increase in future. Recommendations for amending the Orders are based on a desire to preserve the scientific linkage between the Orders and the hydrologic regimes of the two Basins, and improve management flexibility while at the same time having no negative impact. Based on projected climate and associated hydrologic changes, we recommend that the International Osoyoos Lake Board of Control consider the following: 1. Advancing the date on which drought declarations are made in the spring. Given that there may be considerable flow earlier in the season, the first declaration could be made on March 1. 2. Allow more flexibility in filling the lake. Increased flows are projected through winter and freshet is projected to occur earlier. Earlier storage may be required to take advantage of the available water. 3. Allow ramping over a defined period as opposed to setting strict date-specific water level requirements. This will provide flexibility into the future, which is particularly important given the wide range of projections for future water supply. 4. Evaluating whether the distinction between drought and non-drought conditions is required. In its place, a flexible lake management strategy that applies to all years could be developed. 5. Along with an evaluation of the requirement of the drought declaration, the use of fixed-dates for the summer and winter operating ranges should be evaluated in light of the projected future advance of the spring lake inflows. 6. Incorporate an adaptive management strategy that includes re-evaluation of the performance of the Orders every 10 years or after any year, with a view towards periodic refinement of the Orders. This concept recognizes the wide range in projected future conditions. |
| Information Type | report |
| Regional Watershed | Okanagan |
| Sub-watershed if known | Osoyoos Lake |
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| Project status | complete |
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