In 2005, when I was a professor at Idaho State University, the Henry's Fork Foundation Board of Directors asked me to present an overview of hydrology and water management in the upper Snake River basin. Since then, the hydrology and water-management short course has taken on a life of its own, and I give this presentation in some form or another a few times each year. Every time I give the presentation, I update it with new information, particularly as related to climate change and the rapidly changing work of water management and admininstration. My favorite version is the full 3-hour course I give to Idaho Master Naturalist chapters. The 3-hour version allows time for small-group activities and discussion. I taught the course to the Idaho Falls chapter last night, and the group was energetic and engaged. We all had a great time discussing current topics in Snake River water management. A pdf version of my presentation is linked here.
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Cool, wet weather from mid-February to mid-April turned an average water supply into one that is decidedly above average. As of May 9, the Henry’s Fork reservoir system is 94% full and filling rapidly. Based on early-April conditions, summertime water supply in the Henry’s Fork watershed is forecast to be above average. More storage water will be delivered from Island Park Reservoir this summer than in 2017, but higher inflows will compensate, resulting in a very high probability of better-than-average carryover at the end of the irrigation season. April Precipitation 156% of Average Precipitation during the month of April was above average at all 12 weather stations in the watershed and was 156% of average for the watershed as a whole. Below-average temperatures early in the month were offset by above-average temperatures late in the month, and the month ended up within 1 degree F of average. Climate summary for the month of April 2018. Cool temperatures through the middle of April capped a nine-week run of average to below-average temperatures, allowing snow to continue to accumulate until the middle of the month and preventing high runoff until late April. Graph of temperature departure from average so far this water
April 1 snow-water-equivalent was 106% of average in the Henry's Fork watershed. Based on April 1 conditions, summer water supply is predicted to be 108% of average for the whole watershed: 99% of average in the Henry's Fork upstream of Ashton 117% of average in Fall River 114% of average in Teton River Snowmelt is starting at its normal time this spring due to seasonable temperatures. Early-April climatic conditions favorable for water supply In 2016, the spring was both warm and dry, following several dry years, and the result was one of the worst water years on record in the Henry's Fork watershed. In 2017, April-1 snow-water equivalent (SWE) was well above average in Fall River and Teton River subwatersheds but only average in the upper Henry's Fork subwatershed (upstream of Ashton). One reason for the relatively poor April-1 SWE in the upper Henry's Fork was a warm March, which had melted most of the snowpack below 7,000 feet by April 1. Fortunately, the overall water supply in 2017 ended up well above average because of cool, wet weather in April and May. While not as strong in the Teton and Fall river subwatersheds, this year's April-1 SWE was higher
Despite a forecast for conditions that could have resulted in large loss of snowpack yesterday, atmospheric conditions lined up just right to not only avoid the loss but actually gain a very large amount of snow-water-equivalent (SWE). Read on for the details, as well as for an example from the spring of 2010 that illustrates a very large rain-on-snow event. May 2010: What an extreme rain-on snow event can look like As we anticipated the possibility of a rain-on-snow event earlier this week, Ron Abramovich from the Natural Resources Conservation Service reminded me of a large event in the spring of 2010. To give you some idea of the magnitude of that event, the White Elephant SnoTel site received 8.5 inches of precipitation from May 24, 2010 through June 7, 2010. SWE at that site dropped from 13.8 inches on May 24 to 0 on June 2. This means that a whopping 22.3 inches of total water ran off into the upper Henry’s Fork over that two-week period. The spike in streamflow from that event is readily apparent in the following graph, which shows this year's natural flow to date, average streamflow, and that in water-year 2010, which was a
For those following House Bill 496, here is a brief review and update. The concern, as brought to our attention by the Friends of Harriman State Park, is that House Bill 496 could potentially violate the Harriman Gift Agreement (HGA, or "Agreement") condition that requires the Idaho Department of Parks and Recreation staff be chosen based on merit. House Bill 496 would shift the authority to appoint the directors of the departments of Parks and Recreation, Transportation, and Corrections from a Board to the Governor of Idaho. The Idaho State Attorney General has reviewed the bill and has released a legal opinion stating that the bill does not violate the Harriman Gift Agreement. However, as with most legal matters, other opinions are possible. The bill is currently in General Orders where House members will work together until there is a majority consensus to amend it, move it, or vote on it. Because other legal opinions may differ on whether the bill violates the Agreement, we think it prudent that the bill be amended to remove all reference to the Department of Parks and Recreation. If You'd Like to Get Involved If you are a resident of Idaho, you may contact your representatives directly by phone or email to
Over the month of February, water-year precipitation improved from 93% of average to 98% of average, and snow-water equivalent improved from 96% of average to 101% of average. Mean outflow from Island Park Dam over the December-February time period most critical for survival of juvenile trout was 509 cfs, 147% of average and the highest since the winter of 2011-2012. Streamflow throughout the watershed remained above average at most locations. Good precipitation + cold temperatures = improved snowpack February 2018 started out very warm, cooled to near average in the middle of the month, and closed with the coldest 11-day period of the winter. Averaged over the whole month, temperature was 2 degrees F below the 30-year average. Graph of watershed-averaged temperature. Precipitation during February was above average in the upper Henry’s Fork, well above average in the Fall River subwatershed, near average in the Teton subwatershed, and well below average in the valleys. As a result, water-year precipitation improved from 93% of average to 98% of average over the month. This has increased to 101% of average over the first three days of March. Graph of water-year precipitation as a percent of average. Snow-water-equivalent (SWE) accumulation followed the same
The Henry’s Fork Watershed Council, as well as the larger water-management community in Idaho, lost long-time participant Stan Clark, who passed away in his sleep on February 9 at age 89. Stan at a Henry's Fork Watershed Council meeting in 1995. Stan grew up on the family farm south of Ashton, where he subsequently farmed, ranched, and raised his family. Active in water management until the day he passed, Stan participated in the Watershed Council since its inception in 1993 and was a former member of the Committee of Nine, the advisory body for Water District 01. He also served as Chair of the Marysville Ditch Company and was appointed in 2000 by then-Governor Dirk Kempthorne as liaison between the governor’s office and the Idaho Department of Water Resources. More recently, Stan was active in the Eastern Idaho Water Rights Coalition and served on the board of Recharge Development Corporation. Stan was known for his thoughtful, respectful, and insightful input at Watershed Council meetings and other venues. Always an optimist, Stan brought a smile, years of experience, and humorous accounts of earlier days to every meeting. I knew Stan for over 20 years and considered him a mentor. Stan’s
It’s no secret that 2018 has been much warmer than we’re used to (in January, 5 degrees F warmer than normal across the whole watershed and as high as 7 degrees F above average in Island Park). At the same time, HFF has been reporting SWE (snow-water equivalent) numbers at 96% of average at the end of January (as high as 103% of average this past week), above average streamflow, and near average precipitation across the watershed (not to mention 111% of average Jan. precipitation at Island Park). If you’re looking out your window in Island Park right now, you’re probably wondering, “How is that possible?” Here’s the deal. This is a good news, bad news situation. The short version is: 1) we’re concerned about early runoff on the Fall and Teton Rivers (what’s so special about those two?); but 2) there is a good amount of moisture up high (that SWE number) AND 3) these high winter flows and warm temps are just about the most ideal conditions you could ask for in terms of overwintering survival of juvenile trout (READ: we should have a banner recruitment year in 2019). Let’s work through this in chronological order.
Over the month of January, water-year precipitation increased from 87% of average to 93% of average, and snow-water-equivalent increased from 89% of average to 96% of average. Streamflow throughout the watershed was generally above average, including outflow from Island Park Reservoir, which, at 508 cfs, was 134% of average and the highest since the winter of 2011-2012. The only negative aspect of the current water situation is that January was much warmer than average, limiting snow accumulation at lower elevations and setting up the snowpack to melt early and rapidly. A complete guide to the climate and streamflow stations referenced in this blog and my daily water reports is available here. If you would like to receive the daily reports via email, please contact me at firstname.lastname@example.org. January was very warm but generally wet The month of January was very warm, 5 degrees F warmer than normal across the whole watershed. Monthly mean temperature was at least 4 degrees warmer than the 30-year average at all 12 stations I track and as high as 7 degrees above average at Island Park. Pine Creek Pass and Crab Creek stations set new record high monthly mean temperatures. Monthly average temperature at Pine
As the climate warms and water availability becomes more uncertain, the future of wild trout fisheries in the Henry’s Fork depends critically on science-based management that ensures favorable streamflow, good water quality, and a positive fishing experience. Over the past three years, HFF has expanded a small but successful research program run by two full-time staff, with assistance from seasonal technicians and interns, into comprehensive programs in hydrology, water-quality, fisheries biology, and social science, each staffed by a full-time professional and supported year-round by technicians, interns, and graduate students. HFF’s newly developed predictive computer models of snowmelt, streamflow, irrigation demand and reservoir storage provide river users and water managers with up-to-date water-supply information every morning. HFF’s water-quality director has written extensive computer code to process and analyze nearly 2 million individual data points collected each year by our network of automated water-quality sensors. We have recently increased the utility of this network by using the latest high-tech hardware and software to transmit real-time water-quality data from the river to a central server and web site. HFF’s fisheries biologist not only continues long-term operation of fish passage facilities but also uses modern statistical methods to model trout population dynamics and assess