2017 Water Year: South Fork of the American River

//archive SFAR Water Year Forecast March 2017

archive SFAR Water Year Forecast March 2017

 tl;dr: Wet. Very Very Wet.

South Fork American River water year forecast as of March 8, 2017: Wet

The March Water Report was released Wednesday March 8th, with the Water-Year forecast expectedly solidly in the Wet range. Specifically it’s forecasting the American River below Folsom at 7.430 million acre-feet (MAF), with 3.500 or greater being considered Wet. In fact, we’ve already had 4.334 MAF of unimpaired runoff, so even if the heaven’s remained dry through the end of this water year, we’re already locked in on it being a Wet classification.

Guaranteed Minimum Flows

While the March forecast is technically only valid until around April 14th, it’s a reasonable assumption that the following will not change barring an act of congress1.

It’s also worth noting that depending on how quickly/slowly the snowpack melts, there is a strong probability for significantly higher flows (especially between now and mid to late June and even into July) than the minimums stated below.

March-May

  • Monday – Friday: 1,500 cfs 9am-12pm
  • Saturday & Sunday: 1,750 cfs 7am-1pm
  • Minimum Flow: 250 cfs March, 300 cfs April, 500 cfs May

Summer Flows – May 27th through September 4th

  • Monday – Friday: 1,500 cfs 8am-12pm
  • Saturday & Sunday: 1,750 cfs 7am-1pm
  • Minimum Flow: 500 cfs May & June, 350 cfs July, 300 cfs August, 250 cfs September

September 5-30, 2017

  • No guaranteed raftable flows Monday, Tuesday, Wednesday
  • Thursday, Friday, Saturday, Sunday: 1,500 cfs 9am-12pm
  • Minimum Flow: 250 cfs

October Flows

  • No guaranteed raftable flows Tuesday, Wednesday, Thursday
  • Mondays & Fridays: 1,300 cfs 9am-12pm
  • Saturdays & Sundays: 1,500 cfs 9am-12pm
  • Minimum Flow: 250 cfs

November through early February

  • No guaranteed raftable flows Monday-Friday
  • Saturdays & Sundays: 1,500 cfs 9am-12pm
  • Minimum Flow: 250 cfs

The next water year forecast should be released around April 11th, with it taking effect 3 days after issuance.

Reservoir Storage – Of Interest

With a high snow pack and reservoirs on the Upper American River Project (UARP) filling up, here are some2 quick water storage related numbers3 that might be of interest.

As of March 30, 2017 – 1 PM

  • Loon Lake – 6402 ft (spills at 6,418 ft) with 58,515 AF (spills at ~76,500 AF)
  • Ice House – 5,434 ft (spills at 5,454 ft) with 33,233 AF (spills at ~37,120 AF4)
  • Union Valley – 4,855.6 ft (spills at 4,855 ft5) with 226,687 AF (spills at 230,000 AF6)
  • Slab Creek – 1,852.7 ft (spills at 1,850 ft) with 13,710 AF (spills at ~13,350 AF)7
  • Chili Bar –  1,000 ft (spills at 997.5 ft) with a max capacity of just 1,340 AF.

Related Links and References

Show 7 footnotes

  1. I’m not intending to be flippant. It really would take a literal act of Federal Congress to change things.
  2. There are many more reservoirs in the system, these are just the most impactful.
  3. For reservoir storage, current elevation is a hard number, while current storage is a rough calculation based on estimated capacity at that elevation. Natural sediment deposits over time, and from high runoff/melt conditions, can modify (sometimes greatly) actual capacities.
  4. But some data says 43,496 AF
  5. an Ogee gate can be lowered from May 1-Sept 30 raising the spill elevation to 4870 ft. Though when the gate is down they typically will raise it for a controlled spill at around 4,868 ft
  6. Again, May 1-Sept 30 the capacity can be increased to about 277,300 AF
  7. Official data claims 1,870 ft for spill and 16,600 AF of storage, but historical data shows 1,850 ft and 13,350 AF to be more realistic – I’m looking into it.
By |2018-05-25T07:47:55+00:00March 30th, 2017|Current Happenings|

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