The Henry’s Fork Watershed Council held its annual field tour on August 9. About 25 participants met in Ashton to begin the tour, but more people joined later in the day.
The tour started with a trip to one of Idaho Power’s remote cloud-seeding sites in Island Park, where meteorologist Derek Blestrud explained the science and goals of the cloud-seeding program. Full implementation of ground- and aircraft-based operations in the upper Snake River basin is expected to increase annual streamflow by 400,000 acre-feet.
The Island Park Drought Management Planning Committee met on April 8 to discuss projected water supply and management of Island Park Reservoir this spring. Organizations represented at this meeting were Fremont-Madison Irrigation District, North Fork Reservoir Company, Fall River Rural Electric Cooperative, Idaho Department of Fish and Game, The Nature Conservancy, U.S. Bureau of Reclamation, Water District 01, and Henry's Fork Foundation.
As of early February, accumulation of snowpack in the Snake River Basin has reached about two-thirds of its annual maximum, which makes this a good time to assess the current water situation and make some projections for the upcoming spring.
My fishing during calendar year 2015 ended the same way it began: the sun had just dropped below the horizon, ice was beginning to form on my line, and in the last purple light of a short winter evening I could see a pod of trout in front of me, rising to midges.
Photo: Early winter evening on lower Henry's Fork, December 2015.
A few months ago I was contacted by Michael Downey, a water resources planner in Montana's Department of Natural Resources Conservation (DNRC). He had read about a study I directed a few years ago that investigated the effects of development on hydrology and water management in the Henry's Fork watershed and invited me to come talk about this study--and more generally about groundwater management in Idaho--at a day-long technical workshop in Helena. I just returned from that workshop and thought it relevant to share both my presentation and a few interesting observations with you.
Before I leave to speak at the national American Fisheries Society annual meeting in Portland next week, I thought I would provide links to several technical documents to keep you informed entertained for a while.
Wild trout need water of appropriate quantity and quality. Quantity and quality of water released from Island Park Reservoir during June and July of 2015 continue to be the subject of much discussion and concern, particularly following release of around 2,000 cfs July 21-23 to provide flow to test turbines at the Chester Dam hydroelectric project. This blog just covers water quantity, specifically flow releases from Island Park Reservoir.
Back on April 1, with snowpack and winter streamflow data in hand, I predicted that the spring of 2015 would be the driest in the last 35 years and quite possibly the driest since the extended drought of the 1930s. You can read my April 1 predictions at http://henrysfork.org/spring-2015-shaping-be-driest-record. So, how good were my predictions?
It's that time of year when growth of aquatic vegetation (called "macrophytes") begins to fill the stream channel and raise the water depth, even without changes in river flow. Remember that streamflow is the volume of water that flows past a given point on the river per time unit. We usually measure streamflow in cubic feet (volume) per second (time). The depth of the river (measured in feet) is a function of both streamflow and the shape of the stream channel. As macrophytes fill in the channel with plant biomass, there is less room for the water in the channel.