Summer water watch: streamflows low, reservoirs key
Rogue River Basin irrigators who don’t rely on stored reservoir water are in for a dry summer, with streamflows forecast to be as low as one-third of average, thanks to a dry winter, poor snowpack and an expected drier-than-normal summer.
Despite a wet April, with precipitation at 116 percent of average in the Rogue Basin, the basin’s overall precipitation is just 79 percent of average. Snowpack is a hair above half of normal, according to the much-anticipated May Water Supply Outlook Report from the federal Natural Resources Conservation Service.
The May report, which is considered the best touchstone for summer streamflow forecasts, calls for streamflows anywhere from 33 percent of average in the Applegate River Basin to 88 percent of average in the Illinois River at Kerby.
Jackson County Watermaster Shavon Haynes said his office will measure streamflows later this month to get a truer gauge on how stream-side irrigators will fare.
At the same time, however, aggressive filling in Jackson County’s main reservoirs show they currently hold enough water to at least come close to the regular summer water needs of those who rely on them.
“This is the year it’s really going to pay to be a project irrigator,” Haynes said.
A case in point is the Talent Irrigation District, whose three reservoirs hold 78 percent of average water as the district prepares to start delivering irrigation water later this week.
TID Manager Jim Pendleton said his district will draft heavily on Emigrant and Hyatt lakes throughout the summer because flow restrictions out of Howard Prairie Lake will keep about 20,000 acre-feet of water in it.
Pendleton said he expects to meet irrigators’ needs into mid-September. Typically the district stops delivering water in the first or second week of October.
“We’ll get close, but Hyatt and Emigrant won’t look good at the end of the year,” Pendleton said. “A 50 percent snowpack doesn’t do you any favors.”
The federal Climate Prediction Center is calling for warmer and drier weather for the next three months.
Farmers, ranchers and others who are members of irrigation districts pay fees to get their water delivered to them, either from a canal or from natural systems such as Bear Creek. Others draw directly from streams, based on the water right tied to their lands, with earlier water rights given higher priority.
Many Southern Oregon sub-basins contain lands with more water rights than the actual streamflow — called over-appropriated. Some streams like Bear Creek also contain minimum flow levels that must be met before irrigation water is withdrawn.
As natural streamflows decline over the summer, landowners with younger water rights will have their pumps shut off in favor of older water rights.
The Rogue and Applegate rivers have summer flows supplemented from the two U.S. Army Corps of Engineers’ reservoirs, Lost Creek Lake on the upper Rogue River and Applegate Lake on the Applegate River.
While Applegate Basin irrigators were braced for a dry summer, aggressive capturing of winter and spring inflows now has Applegate Lake just 2 ½ feet from full. And despite inflows of just 79 percent of average, Lost Creek Lake was full this week.
Together those two projects should provide enough flows at key times to protect migrating spring chinook and, later, fall chinook in the Rogue and Applegate rivers.
Fisheries enhancement is a primary summer purpose for releases from Lost Creek and Applegate lakes, each of which have water stored precisely for those purposes.
Pete Samarin, a fisheries biologist who helps craft Lost Creek and Applegate releases, said the stored Applegate water is enough to keep outflows at 250 cubic feet per second throughout the summer.
That’s enough to sustain juvenile fall chinook and draw fall chinook up the Applegate all the way to the dam, Samarin said. Fall chinook likely would not get past Murphy Dam without those supplemented flows.
In the Rogue River, flows should be high enough through June to stave off warm-water disease outbreaks in the Lower Rogue during the ongoing spring chinook migration, Samarin said. Enough stored water should be left to do the same for fall chinook in August and September, he said.
July and August flows in the Rogue, however, will be very low, Samarin said.
Should Lost Creek Lake run out of water for chinook, the agency will ask the Corps to draw the reservoir below its normal low-pool volume. The agency did that during the drought of 2015.
Reach Mail Tribune reporter Mark Freeman at 541-776-4470 or firstname.lastname@example.org. Follow him on Twitter at www.twitter.com/MTwriterFreeman.