Back country roads will soon be passable especially after maintenance and drying out. The Idaho Department of Fish and Game has established a “Catch and Release Season” on certain streams that will become approachable. Refer to the Department’s on line or hard copy 2022 fishing regulations to see which waters this season applies.This season extends to the opening of general fishing season.
We are in a period of “BWO” weather. If you can stand the accompanying wind and precipitation, afternoon top water fly fishing can be worth a visit along the lower river. . Dress warmly and wade carefully! Banks are clearing making access an improving situation. Presenting streamer and stone fly nymph patterns will also bring action during this period of relatively good overhead cover.
Excerpts from Dr. Rob Van Kirk Henry’s Fork drainage SWE report of this morning are below. It contains some long awaited good news.
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As mentioned yesterday, we could have used our current weather back in February. Mean temperature yesterday was 9 degrees F below average and roughly equal to average at the end of February. Precipitation overachieved for a change and was the highest one-day total since January 6, the last day of the only extended wet period we had all winter. Precipitation totals ranged from 0.11 inch at Rexburg to 0.8 inch at White Elephant and averaged 0.38 inch over the watershed. This was enough to move the water-year total from 78% of average to 80% of average.
Cold temperatures put a temporary end to snowmelt, and all SnoTel stations except Island Park gained snow water equivalent (SWE) yesterday. New SWE ranged from 0.3 inch at Crab Creek to 1.3 inches at Phillips Bench and averaged 0.6 inch over the watershed. This moved SWE up two percentage points to 67% of average. It also moved SWE back ahead of 2001 and 2015, the two years with lowest SWE in the 1989-2022 record. SWE on the ground this morning is the highest for the season so far at all high-elevation stations and most of the mid-elevation stations. Date of peak SWE for the whole watershed is still March 22, but tomorrow’s SWE will most likely be the new peak for the season. Average peak date is April 12.
Very cold and unsettled weather will continue for another few days. Although temperatures will warm, precipitation remains in the forecast off and on into the beginning of next week. The 7-day quantitative forecast calls for 0.25 inch along the western edge of the watershed, 0.5-0.75 inch in the Island Park area and up to 1.75 inches along the Wyoming border. That will be enough to keep the water-year total up above 80% of average and is likely to push SWE up to 70% of average. Snowmelt will remain minimal at least through Friday.
After a small, short-duration bump, natural streamflow dropped yesterday in response to cold temperatures over the past two days. Natural flow is 71% of average: 76% in upper Henry’s Fork, 68% in Fall River, and 62% in Teton River. I expect natural flow to stay pretty constant for the next few days.
Due in part to direct precipitation on the reservoir surface, Island Park Reservoir gained 444 ac-ft yesterday to each 93% full, compared with 86% full on average. Outflow will likely be increased again to prevent reservoir ice from encroaching on spillway infrastructure as the reservoir continues to fill.
Early this AM flow out of Palisades Dam was upped from around 890 cfs to 1270 cfs and is increasing. Larger flow out of the reservoir will impact the river on downstream and the main stem Snake River above American Falls reservoir. Although the reservoir is slightly more than one third full and run-off flow coming in is around 3000 cfs, water is being released to spread irrigation demand through the system.
Flow out of American Falls Reservoir is in an increasing mode as downstream irrigation demands for water are beginning. Yesterday flow was increased from around 440 cfs to 1180 cfs. Wading downstream of the dam can be dangerous during increasing flows. If you are fishing within earshot of sirens and whistles coming from the dam, get out of the water ASAP!
Flow out of Mackay Dam is about 75 cfs. Water management priority is to fill Mackay Reservoir, so look for low flows until irrigation season begins. The low flow makes for easy wading and concentrates fish into deeper water. Broken snow and ice prevails along banks and is receding. Midge and BWO life cycle, small bead head nymph, medium sized woolly bugger, and peacock leech patterns bring action.
With Palisades Reservoir filled about one third of capacity and out-flow about half of in-flow, it is going to take a lot of run-off to come close to filling before irrigation season begins. Outlook for enough snow accumulation needed to do so becomes more unlikely with passing days. So it looks like current flow in the river below Palisades Dam ( 874 cfs at Irwin, 1300 cfs at Heise, 700 at Lorenzo) will hold well into run-off season.
Under current water conditions (cold and clear), the best fly fishing strategy is to present streamer, nymph, and rubber leg patterns into deeper holes and runs using full sink or sink tip lines and stout leaders. Consider that winter is the toughest time for fish to survive. Therefore using stout leaders allow them to be played more quickly giving a better chance for survival after being caught and released. The river needs to warm for any good top water fishing to take place.
At the first off April, flow will be shut off in the Dry Bed for irrigation structure maintenance. During this time IDF&G allows a salvage situation there where fish may be harvested by any legal means rather than being wasted. Consult current on-line or hard copy fishing regulations for salvage specifics.
Excerpts from Dr. Rob Van Kirk’s Henry’s Fork drainage water report of this morning are below.
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Mean temperature yesterday was 2 degrees F below average, extending a streak of nine consecutive days of temperatures at or below average. With snowpack as low as it is, cold weather is critical to keeping that snow on the ground as far into the spring as possible. After a dry day, snow water equivalent (SWE) dropped back to 69% of average yesterday, while water-year precipitation stayed at 83% of average.
Current SWE is still ahead of that for the date in 2001 and 2010. Subsequent spring and summer weather differed substantially between those two years, resulting in two very different outcomes for the water year as a whole. April-September precipitation in 2001 was 21% below average, while that in 2010 was 19% above average. That difference resulted in 2001 ending up with the lowest natural streamflow in the 1978-2021 record, at 73% of average, compared with 75% of average in 2016 and 76% of average last year. By contrast, natural flow in 2010 ended up at 87% of average, ranking above the 33rd percentile of water years since 1978. So, a wide range of outcomes is still possible, although anything close to average water supply is not one of them.
Light precipitation is expected this afternoon through tomorrow and again on Saturday night and Sunday. Total precipitation amounts over the next week are expected to range from around 0.1 inch along the western edge of the watershed to around 1 inch along the Wyoming border. If those totals are realized, precipitation this week will be about the same as it was last week and close to average for mid-March. Temperatures are expected to stay near average. After that, above-average temperatures are in the forecast beginning next Tuesday, although long-range outlooks do not show any strong indication that either temperature or precipitation will deviate much from average.
Stream gages are starting to come back on line after a very long period during which ice has prevented real-time flow observations. The St. Anthony gage on the Henry’s Fork and Ashton gage on Fall River are the first two to return to real-time transmission. Based on data available as of yesterday, natural streamflow is in the range of 75-80% of average in both the upper Henry’s Fork and Fall River.
Island Park Reservoir gained 232 ac-ft yesterday and is 87% full, compared with 80% full on average. Reservoir content will reach 120,000-123,000 ac-ft by April 1.
Rob Van Kirk, Ph.D.
Senior Scientist
P.O. Box 550
Ashton, ID 83420
208-652-3567 OFFICE
208-881-3407 CELL
208-652-3568 FAX
There is access at several places along the river above American Falls Reservoir. Some include below Gem Lake Dam, around the Shelley I-15 connector, near the Firth boat launch, the Riverside access just below Blackfoot, around Tilden Bridge, and near McTucker Ponds. In all these locations river flow is lower than normal and water is clear. Presenting streamer patterns gives the best chance of success. Below American Falls Dam it’s a bit different. Some access is through muddy roads. The reservoir is about two-thirds full and low flows in the river below (currently about 450 cfs, but somewhat discolored) will continue until it is at capacity.
Nicer but unsettled weather is predicted for the coming week. With increasing BWO activity on the lower river, some decent top water fishing should take place but river still has limited approaches. Streamer and stonefly nymph patterns remain effective when presented in deeper runs and holes where you can get to them..
Excerpts from Dr. Rob Van Kirk’s Henry’s Fork drainage Snow Water Equivalent (SWE) report of yesterday, March 11th, are below. The data give a grim picture of current SWE in the area.
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Yesterday morning was the coldest in the watershed since December 17, 2016. In the 12-station 1989-2021 record I use for the whole watershed, yesterday’s minimum, mean, and maximum temperatures all set new records for the date. The low of -16.5 degrees F broke the old record of -3.2 degrees set in 2006. The daily maximum of 17.0 degrees broke the old record of 21.1 degrees, set in 2009. The daily mean was a whopping 27 degrees below average for the date and the second coldest day of the winter, behind January 1. That beat the old March-10 record by 9 degrees. Even at stations with very long periods of record, yesterday’s low temperature broke records for the date by wide margins. Idaho Falls set a new record low of -7 degrees, breaking the old record of 4 degrees, set in 1969.
No precipitation was recorded yesterday, dropping the water-year total to 82% of average. Snow water equivalent (SWE) stayed at 68% of average. After another day of below-average temperatures, forecasts and long-range outlooks all call for temperature and precipitation near climatological averages. In the short term, light precipitation is expected on Sunday, with slightly heavier precipitation on Tuesday and Wednesday. The latest 7-day precipitation forecast looks a little better than it did yesterday, with 0.25-0.5 inch expected over most of the lower elevations of the watershed and up to 1.25 inches along the Teton crest. If realized (big if), that would be roughly average for this time of year.
As you might imagine, stream gages throughout the watershed remain affected by ice. The Island Park and Ashton gages are the only two that have provided reliable data all winter, and both show natural flow in the upper Henry’s Fork at around 75% of average.
Reservoir fill rates were even lower yesterday than they were on Wednesday. Island Park Reservoir is 86% full, compared with 79% on average, and the three reservoirs in the watershed are 87% full, compared with 84% full on average. The upper Snake River reservoir system is 50% full, compared with 74% full on average.
Rob Van Kirk, Ph.D.
Senior Scientist
P.O. Box 550
Ashton, ID 83420
208-652-3567 OFFICE
208-881-3407 CELL
208-652-3568 FAX
Springfield Reservoir is producing some fishing success even though water remains cold ( mid 40’s in degrees Fahrenheit). Leech and small nymphs patterns and fly rod jigs presented on intermediate lines work. Try suspending small nymph and midge pupa patterns under an indicator on a floating line to find the taking depth.