Thanks Idaho Trails Association and letting me camp, work and watch the Selway River rise and fall this May. Here’s a summary about the climatic conditions (daily/weekly weather, cold & warm fronts, record high day & non-freezing night temps, snowmelt rates, lack of spring precipitation) that produced this spring’s Selway River hydrograph shape. It’s a complex world out there. Hopefully this helps explain the diurnal river changes and why our rivers flow the way they do as our winter snowpack melts in the spring.
Current neutral ENSO conditions are predicted to change into La Nina conditions for this winter. Weak or strong La Nina? It doesn’t really matter in years following a strong El Nino like last year.
Following is a summary of the different outlooks, explanation of current conditions, and reading material if you can’t sleep or just interested in learning about these relationships. You can skip to the end for the summary to see what happens in winters following strong El Ninos or here it is…
What an event it was that added much needed moisture to many Idaho rivers. Following is a statewide summary about the impacts of this early June Atmospheric River Event. This rain on snow event increased streamflow in many rivers across the state that will push recession flows out a bit.
Combining daily rainfall and snowmelt resulted in 2.5 to 3.0” of Total Runoff Available at a few SNOTEL sites. The cool May temps delayed snowmelt allowing snow to remain in higher elevations that provided a runoff boost with the falling rain.
What a storm it was – who do you thank ? Those benefiting include fish, wildlife, river runners, salmon flows, hydropower production and more. The streamflow boost created another flow increase that will keep recession flows higher longer. However, some basins missed the positive impacts from this event. See the following analysis to see why some rivers benefited while others continued with their downward recession trend.
Benefits include assisting with final fill of some reservoirs, delayed irrigation water use that may even result in better reservoir carryover storage for next year. Impacts include challenges for those on rapid rising rivers especially for those adventuring on the MF Salmon River and experiencing the New Velvet Rapid up close.
With the return of warm temps, rivers are rising again. The last cold front slowed the melt down to a few tenths per day and increased to 1.4″ yesterday with temps reaching 67 F at Deadwood Summit. With these yoyo like temps and some precipitation remaining in forecast, expect a few more ups n downs in flow levels before full recession starts.
Snow Weather and Flow 