Dobson Engineering. (1990). Powers Creek- Assessment of Alternatives to Enhance Okanagan Lake Fishery. Kelowna: Dobson Engineering.
Powers Creek is located on the west side of Okanagan Lake at Westbank, opposite the Okanagan Mission area of Kelowna. The watershed has a drainage area of approximately 144 km2. There is an historic use of the creek for spawning and rearing of both rainbow trout and kokanee from Okanagan Lake. The intent of this report is to detail the opportunities that may exist to enhance either or both of the existing species through improvement of the water supply.
This report identifies the reaches of the stream that are accessible to the fish and the flows required to maintain spawning and rearing. Based on the required flows, for both trout and kokanee, the deficits will be determined using both the mean monthly and the one in 10-year low flows as indicators.
Once the deficits in flow have been determined, the available alternatives will be identified to supply the additional water needed to achieve the optimum flows.
Included in the assessment is: the present licenced use of the stream, a survey of the water licences with regards to their level of use, and the projected full utilization of the existing water licences.
Finally, a recommendation will be made regarding the cost effectiveness of each flow enhancement option and the consequences of failing to provide these flows.
Powers Creek is estimated to be the second most important rainbow trout and Kokanee fishery on Okanagan Lake. The deficits for kokanee occur first during a one in ten-year low flow at the current level of use of the water licences. When the water licences are fully developed, the shortfall in worsened.
The top two most feasible alternatives for increasing flow for the fisheries are:
- The transfer of the Byland’s Nurseries Ltd. Unused water licence. These two licences don’t amount to a lot of flow but they are not being used and the transfer to the fisheries program will ensure that they would not be re-activated. The point of diversion is located within the spawning reach of the creek which is undesirable. Preliminary discussions with the licencee have indicated a willingness to consider a transfer.
- The opportunity to take advantage of the existing pumping facility belonging to Byland’s Nurseries Ltd. should be investigated in detail. This system is licenced on Okanagan Lake and might have a capacity near what is needed to supply the fishery flows. If the nursery plans to continue to use the system, there may be some opportunity for a joint use. The advantage of this option is that the works are already in place and could be modified at a cost much less than establishing a separate system. The plans by the nursery for their lands that would be irrigated from the pump facility are not established. Prior to entering into discussions regarding the transfer or joint use it will be necessary to establish what the capacity of the works are and what additional works would be required. If it was agreed to use the system, the fisheries program would have to apply for a water licence to cover their intended use.
Options to satisfy short term flow requirements
The short terms is considered to be the situation at current utilization of the water licences on Powers Creek.
Mean monthly discharges are adequate for the kokanee. Although, the one in ten-year flow event causes September to have a major deficit.
Mean monthly discharges are adequate for the trout. Although, the one in ten-year flow event causes July and August to have major deficits and minor deficits in October.
Options to satisfy long term flow requirements
Long term implies the full development of the water licences within the watershed.
At full utilization there would be a minor deficit in September during a normal year and deficits in six months of the year during a one in ten year low flow scenario.
For the kokanee, the production would be reduced in the long term due to the inability of the system to carry large numbers of fish at low migration and spawning flows.
Major deficits would occur in July and August in a normal year in the long term scenario. In the one in ten year scenario, all of the months would have a deficit except during the spring freshet.
Over the long term the trout fishery would be reduced to a very low level if it survived at all.