March has been a good month in terms of mitigating the risk for high spring runoff flows in Provo this year. Warm, wet weather (followed by cooler temperatures) in recent weeks has reduced mountain snowpack at low and medium elevations, without generating any significant runoff. While in early February, snowpack was universally near 200% of normal, low elevation snow is now slightly below average for this time of year and mid-elevation snow is about 150% of normal. Snowpack at higher elevations is still twice normal amounts.
- Cascade Mountain peaked a month ago at 22” and is now at 18”
- Timp Divide peaked three weeks ago at 33” and is now at 28”
- Trial Lake is at 45” and has not yet peaked
Normal snow pack this time of year is 20” – 24”.
The anticipated warm weather later this week with temperatures in the 70’s, followed by cooler weather is the best case scenario to minimize peak flows. While temperatures and precipitation over the next two months will still have a significant impact on runoff, following are our current expectations:
Utah Lake – The lake elevation is currently 4’ below compromise (normal elevation), up more than 3’ from the low point last fall. It will likely rise another 2-3’, but not quite back to compromise elevation.
Provo River – Flows in the lower Provo River are currently in the 400 cfs (cubic feet per second) range. Flows above 1000 cfs, in the 1200 – 1800 cfs range, will likely occur in May. The timing and duration of those flows will be largely influenced by how quickly Jordanelle Reservoir fills this spring (it is currently at 70% of capacity).
Frontal Canyons – Two weeks ago, with the warmer weather, water was flowing out of Little Rock Canyon and dissipating just below the mouth of Rock Canyon. Those flows backed off with the cooler weather that followed. Warmer weather later this week will likely start those flows again. Subsequent cooler weather will keep them from getting too high, too fast. Sustained flows will occur with a week or more of consistent warm weather, however, those flows are expected to be within manageable levels.
Maintenance and tree removal along the lower Provo River has been occurring over the last couple of weeks, and will continue to maximize channel capacity.
Thanks goes to Greg Beckstrom for the update. I plan on sharing another update as conditions warrant.1