Dolores River Release Updates for April 2016 - CO

Over the past several months, AW and our partners in the Dolores River basin have been studying anticipated runoff and inflows into McPhee Reservoir in Southwest Colorado, and discussing how best to provide optimal paddling condition n the lower Dolores River. The most recent forecast was released Today, and a summary of earlier forecasts follows below.

Tuesday, April 26, 2016

Although Colorado’s upper Dolores Basin caught some of the April 15 -18 storms that dumped nearly 4 feet in some parts of the State, the April overall precipitation fell a little below normal.   The Colorado River Basin Forecast Center has since dropped their most likely run-off expectations in the Dolores River (50% probability based on current conditions and 30 year record) by another 20,000 Acre-feet.

What this means for paddlers is that we need a little help - above average precipitation over the next month - to fill McPhee and make some excess water available for a boating release. Though the runoff has started and the upper Dolores is running up around a 1,000 CFS it will be 3 to 4 weeks until McPhee Reservoir nears full capacity before a release is made. If the runoff comes in higher than currently forecast, Water Managers will announce a spill about one week ahead of the start and give ramping days and duration at higher flows of 1,000 to 1,200 CFS, likely about 5 days. A release of boating is shaping up to occur around Memorial Day if it comes at all.

HOWEVER: Using the most probable forecast from the CBRFC, the US Bureau of Reclamation’s subject operating plan for McPhee Reservoir indicates a controlled release of only and approx. 6,500 acre foot.   As released by BOR in an April 20th statement to AW, “there are too many variables to actually predict a managed release of this size.  A 6,500 acre foot release is not enough to provide rafting flows so (BOR) have used the water to facilitate fish sampling for a short period in June.”

By law, the BOR’s Dolores Project (including McPhee Dam and Reservoir) committed to minimizing the Project’s impact to paddling in the Lower Dolores River, by releasing water in advance of filling the reservoir.  By law, and in AW’s view, any release of anticipated surplus water MUST be made for the benefit of public rafting, kayaking, and canoeing. We are watching the May 1st CBRFC forecast, and developing legal strategies to enforce the Projects obligations to boaters. Stay Tuned...

Earlier April Forcasts:

Wednesday April 13, 2016

Early April has improved our weather patterns compared to March, and brought some new precipitation to the mountains. Last week's warm temperatures started the April runoff and a little rain on snow over last weekend jumped up all the local river flows and snow melt. This can be seen in the Lost Canyon gage into McPhee and the gages downstream of McPhee at Slickrock & Bedrock. All the lower snow, below the 9,000 foot elevation, appears to be melting and running off pretty close to normal patterns. This bump in river flows last weekend appears to be slowing down again, partially due to some cool weather at higher elevations and also partially due to the available lower snow having melted out.

The forecasted weekend storm looks promising and could boost inflow if it hits big in the upper Dolores as forecasts are starting to indicate. We remain working off the April 1 forecasts from the Colorado Basin River Basin Forecast Center (CBRFC), which produces a range of potential runoff probabilities based on future weather conditions through the April to July runoff period based on current conditions and past records. They do not always accurately know all local conditions including the extent of our lower snow pack in the Dolores. They generally have a plus or minus 15% on the McPhee inflows. If runoff falls on the plus side we'll have a spill, no spill if runoff falls on the minus/low side. 

Next CBRFC forecast should be out on May 3. So... we still need 105,000 AF to fill McPhee Reservoir, at least 30 plus days of inflow, so no spill in early May. Cold, snow vs. rain & clouds vs. sun combined with our small amount of dust on snow will control how fast McPhee fills, but we should have a week's notice before having to spill.

3/5/16 Update: March storms came up a little below average and the snowpack started to melt, then stopped and built back up a few tenths of SWE. The end result was the forecast drifting lower and somewhat flattening at the end of the month.

The 50% Most Probable (MP) Forecast based on April 1 snowpack came in at 250 KAF, while the 70% Forecast came in at 220 KAF. The MP at 250 KAF provides a small managed release (spill) for about a week. The 70% spill will not produce a boating release if it comes down in atypical pattern. We will not plan to start this release until the reservoir elevation is between 6920 and 6922. Today McPhee is at elevation 6895 and we do not expect to reach release levels until late in May. The runoff is just starting and will rise and fall with temperatures. Upper Dolores flows usually hit their peak near May 20, a likely time for us to reach near full if the runoff comes off normally. Temperatures, new storms or dust on snow can all affect the runoff timing.

So a small spill still remains possible. It will not be definite until later in May and will be short, 5 - 10 days max, with about one week's notice before it starts. We will operate as a "fill in spill", and start releases when we approach full at 6924, available on Lake Elevation tab. Runoff timing, early vs. late, along with future weather will drive the specific size and timing of any excess water spilled downstream. We will update again in several weeks close to May 1 as new information, such as precipitation, becomes available.