The Okanagan Lake Regulation System is a multi-lake, multi-purpose system, owned by the Province and managed and operated by the Ministry of Forests, Lands and Natural Resource Operations.
The system is a tributary to the Columbia River in the United States (see map). The system extends from Kalamalka Lake to the north end of Osoyoos Lake and includes:
- four dams (Kalamalka/Wood, Okanagan, Skaha and Vaseux lakes)
- 17 vertical drop structures
- 38 kilometres of engineered channel, including 68 km of dikes, and four sediment basins.
Okanagan Lake is a large storage reservoir with a normal operating level that seasonally varies by about 1.2 metres.
The annual water flows for Okanagan Lake are dominated by runoff from spring snowmelt, which is highly variable from year to year. Annual inflows can range from 78 million cubic metres to 1.4 billion cubic metres. The biggest contributor to Okanagan Lake is Mission Creek, accounting for 30% of its annual inflow.
Each spring, inflow volume forecasts are estimated by the ministry’s River Forecast Centre. These forecasts use precipitation data, lake elevation and snow data. These forecasts combined with real-time data of lake levels, flows and other factors, are input to the ministry’s fish water management tool (FWMT) to plan and track the annual operation of the Okanagan Lake Regulation System.
One of the ministry’s annual objectives is to bring the Okanagan Lake level to the target upper elevation (referred to as full pool) of 342.48 metres above sea level by the end of the freshet period.
All local governments in the Okanagan have adopted the Okanagan Basin Implementation Agreements, which recommend establishing a flood construction level of 343.66 metres above sea level. This level is 1.18 metres above the upper target level for Okanagan Lake.
The 2017 freshet has seen unusually high inflows. The wet fall and late snow has put snow pack levels at 147% of normal, as of May 1, 2017.
Ministry staff have been releasing water at the maximum rate within operational constraints for weeks to try and make room in the system for more water. However, high snow pack, along with saturated soils and thunderstorms, have created very high inflows into the lake. Localized flooding around the lake and along the Okanagan lakes and river are anticipated.
Ministry staff are working with local governments and Emergency Management BC to anticipate potential flood levels and prepare for flooding.
Flood prevention tips: http://www.gov.bc.ca/preparedbc/floods/