Lake Evaporation


Section 8.0 of the report (13Kb PDF) describes the investigation of lake evaporation conducted for Phase 2.

The Penman-Monteith model was chosen for estimating evaporation from Okanagan Lakes, but due to a lack of direct measurements, the accuracy of the evaporation estimates is given within a fairly broad range.

It is recommended that direct measurements of lake evaporation be obtained so that evaporation can be modelled with greater precision.

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Three large yellow buoys – 3 metres (10 feet) tall by 1.8 metres (6 feet) wide – were deployed on Okanagan Lake to monitor lake evaporation for the next three years.Photo courtesy: Shoreline Piledriving

Monitoring Lake Evaporation:

The Okanagan Basin Water Board is pleased to be partnering with Environment Canada on an important study to better understand what is happening to the Okanagan’s water supply.

In late July, the OBWB and Environment Canada launched three large yellow buoys – 3 metres (10 feet) tall by 1.8 metres (6 feet) wide – on Okanagan Lake to monitor lake evaporation for at least the next three years.  Each buoy is equipped with special computer monitoring software that will measure relative humidity on the lake surface, intensity of the sunshine, different temperatures and wind levels, and how evaporation on the lake is affected by these elements.

This study comes as the result of work done on the OBWB’s comprehensive Okanagan Water Supply and Demand Project, a three-year, $3 million project that looked at the valley’s water supply and found at least one piece of the puzzle missing… How much water is lost off Okanagan Lake through evaporation?

Initial estimates put lake evaporation at one metre per year.  But the Okanagan is known to be a region with water supply challenges and estimates aren’t good enough when we are trying to effectively manage our water resources.

By determining how much water is lost to evaporation, the Okanagan will be in a better position to plan for these challenges, including drought.

The buoys have been placed in the middle of Okanagan Lake.  One buoy is located approximately 4 km north of the Okanagan Centre boat launch in Lake Country, a second is in West Kelowna across from The Cove Resort, and a third is about 4.5 km north of the Summerland boat launch..

The buoys include a flashing light that emit five flashes in 15-second intervals.