This article was published on: 08/7/20 12:00 AM
By Tod Heisler
The generation of hydropower in irrigation canals has long been heralded a win-win solution for both irrigators and rivers.
As the story goes, piping irrigation canals conserves as much as 50% of the water diverted from the river and enables the installation of in-conduit hydroelectric facilities. The conserved water can be left instream for the benefit of fish and wildlife and the hydro revenues can help pay for the canal piping. This all sounds good, but in-conduit hydropower creates a strong economic incentive to divert water from the river, not restore its flows in an ecologically meaningful way.
When approving conditional use permits for hydroelectric facilities, Deschutes County requires “a declaration by the applicant that water diversion for power generation will not cause water flow in the affected stretch of the river, to fall below the minimum streamflow for that stretch as recommended by the Oregon Department of Fish and Wildlife (ODFW).” Three Sisters Irrigation District diverts water from Whychus Creek, and significantly reduces streamflow and increases water temperature in the whole creek below its diversion.
As the largest single diverter on Whychus Creek with more than 150 cubic feet per second (cfs) of water rights, TSID adversely affects the stretch of river from its diversion to the point at which Alder Springs enters the creek 24 miles downstream.
In order to meet the minimum flows ODFW recommends for this stretch of Whychus Creek, TSID needs to assure that at least 33 cfs is instream down to Alder Springs. Despite a $50 million investment of public funds in canal piping and the construction of a hydroelectric facility, instream flows below TSID’s diversion are far less than the ODFW recommendation.
Streamflow measurements taken this summer by Oregon Water Resources Department in the city of Sisters indicate that between July 14 and 28, flows dipped to between 10 and 15 cfs on nine separate days, far below the recommended 33 cfs ODFW minimum flow.
TSID’s publicly financed new infrastructure is in place and the district possesses full capability to take care of the creek and still deliver a large volume of water to its patrons. They failed to do so, in part, because hydropower creates an incentive to divert from the creek rather than to restore its flows.
The installation of hydroelectric facilities in conjunction with irrigation canal piping could be potentially beneficial, but unless these projects are coupled with permanent, enforceable stream flow restoration agreements, the hydropower will be detrimental to the river. It creates a strong economic incentive to divert as much water as possible throughout the irrigation season rather than divert only the water needed to fulfill an authentic agricultural need.
Swalley Irrigation District (SID) is a good example of this. Irrigation water rights typically have seasons that extend to the end of October. SID is a small urbanized irrigation district with very little agriculture. Its hydroelectric plant becomes the primary reason to divert water right up to the last day of irrigation season. Small parcels in the High Desert with a short growing season do not generally need to be irrigated through the month of October.
For the region’s iconic fish species, however, October is a very important month. In October, Chinook salmon need adequate stream flows to spawn, rear juvenile fish and allow for outmigration to the ocean. Steelhead and redband trout also need flows for juvenile rearing as well as steelhead migration. ODFW recommendations for October minimum flows are 50 cfs in Whychus Creek and 250 cfs in the Middle Deschutes River. Last October, daily mean flows much of the month in Whychus and the Middle Deschutes were less than half of this ODFW minimum.
It is high time to give our rivers and streams a higher priority for water than the generation of hydroelectric power in irrigation canals.
Tod Heisler is director of the rivers program for Central Oregon LandWatch.