Dolores River Operations Report 2005 River Season

--Carolyn Dunmire, Dolores River Action Group

On a Tuesday evening in mid-November, a group of farmers, boaters, anglers, scientists, and government officials gathered at the Dolores Community Center to review Dolores River Operations for the past water year. It is a little strange to consider the “operation” of a river, as we usually don’t have the opportunity to evaluate Mother Nature.  However, as a dam-controlled waterway, the Dolores River is indeed operated by the Dolores Water Conservancy District (DWCD) and the Bureau of Reclamation.

The Operations Meeting hosted by DWCD/Bureau of Reclamation Operations Committee is generally held in years when there is a “spill” or release of water from the dam because the reservoir is filled to capacity before the spring run-off has ended. 2005 was such a year. The first time the dam has spilled since 2000. Your evaluation of this year’s river operation will likely depend on your perspective.

If you were a boater watching the river level drop from 3,000 cubic feet per second (cfs) to under 1,000 cfs on Saturday night over Memorial Day weekend—you probably were unhappy with river operations. Although, overall, most boaters were ecstatic to have any water in the river after waiting 5 long years for a spill.  Irrigators were likely pleased with reservoir operations this year as the reservoir was completely full into July. Although, DWCD did not reach their target for water sales this season. Finally, if you happen to be a trout or native fish living in the Dolores River, you might be feeling pretty lonely, as your numbers continue to decline even with increased river flows this year. All of these perspectives were addressed at the meeting. 

Operating Criteria
Vern Harrell of Bureau of Reclamation opened the meeting with a summary of McPhee Reservoir Operations for 2005. His first slide turned out to be one of the most important and often overlooked aspects of river operations: the operations criteria. While these operations criteria spell out the obvious – the reservoir is operated to maximize availability of water in the reservoir for irrigation – there were some subtleties that came into play during 2005.

McPhee Reservoir Operations Criteria Summary
1) Fill the reservoir when possible.2) Do not allow the reservoir to exceed elevation 6,920 feet prior to the end of May. (Full reservoir is elevation 6,924 feet).3) Manage releases to provide white water boating opportunities, when possible.

• Try to peak releases over Memorial Day weekend.

• Provide a minimum raftable release of 800 cubic feet per second (cfs) as long as possible.

• Try to limit releases to less than 4,000 cfs.

4) Provide a minimum of 2,000 cfs for seven days for channel maintenance.5) Manage releases in such a way that it is not necessary to use the emergency spillway. (Maximum release through dam outworks is 5,000 cfs).6) Managed spill releases end when reservoir inflows match the project demand. Managing a river during spring run-off is not as easy as following the operating criteria 1-2-3. 

The operations plan for any given water year begins with a runoff forecast. Forecasting runoff especially for a river as under-monitored as the Dolores, is more of an art than a science.  Bureau of Reclamation has access to some of the best forecasting tools in the US. Brenda Alcorn, a senior hydrologist from the Colorado River Basin Forecasting Center (part of the National Oceanic and Atmospheric Administration) explained the forecasting tools used to predict runoff for the Dolores River as well as the data required to make confident predictions. She noted that “the Dolores Project is relatively new” and does not have the 30 years of historical data required to run the Water Supply Forecast model.  Alcorn and the other forecasters for the Dolores River use other models and data sets to make predictions for Dolores River runoff. These forecasts are improving with data from a new snotel (snow gauge) in Bear Creek and as each additional year of flow data are added to the historical record. There is one thing you can be sure of with forecasts – they will be wrong. And this year was no exception. While the runoff forecast predicted the total amount of runoff correctly, the water came down faster then anybody expected. The river peaked over a relatively short five day period that just happened to coincide with Memorial Day weekend. 

Memorial Day Perfect Storm
This is where the subtleties of the operating criteria come into play. Fostered by the date of runoff peak flow, reservoir elevation requirements on June first, irrigators turning on their systems, and one of the biggest boating weekends on record, a perfect storm formed over Memorial Day weekend resulting in DWCD/Bureau of Reclamation cutting the release flows in half overnight and leaving many boating parties surprised and potentially stranded in the river canyon. After an hour of discussion at the Operations meeting, it became clear what had happened. Bureau of Reclamation followed the operating criteria. This should not have been a surprise to anybody, however, several of the criteria combined to result in the dramatic drop in river flow. 

First, the inflow to the reservoir peaked on May 23 at over 5,000 cfs. Almost immediately, the inflow began dropping so that three days later it was half the peak flow and would obviously not be increasing again this season. This inflow pattern initiates the end of the spill as specified by the last of the operating criteria “spill releases end when inflows match irrigation demand”. The weather during Memorial Day weekend was beautiful, which explains why the inflow was so high – it was hot and dry and the snow in the mountains was melting fast. This weather pattern also prompted irrigators to turn on their systems because their alfalfa was starting to dry out and it was time to water. This resulted in a large increase in project demand or water being diverted out of the reservoir for irrigation. According to the operating criteria, the spill would have to be cut back so total outflow (spill + irrigation) would match the inflow. Finally, the requirement for filling the reservoir is added to the mix. 

Bureau of Reclamation keeps the reservoir four feet below full until the end of May, but on June first the reservoir should be full. With the inflow dropping fast and the reservoir still needing 16,000 acre-feet to fill, Bureau of Reclamation needed to stop outflow and fill the reservoir. All of these factors: greatly reduced inflow, greatly increased project water demand, and the need to fill the reservoir combined to cause Bureau of Reclamation to cut back on the release. The operating criteria would have allowed the Bureau to reduce the release to much lower levels, however, Harell pointed out that they did not drop the release below 800 cfs so they would not strand rafters in the canyon. Although some boaters relayed that they were essentially stranded because the drop in water level was so rapid that they woke up Sunday morning to find their boats high and dry. 

An hour of discussion and comments about river operations over Memorial Day uncovered some ways to “do it better next time”. Primarily, the solution is to improve communications between DWCD/Bureau of Reclamation and boaters. Some ideas include 1) regularly updated release forecasts that have some discussion about the confidence or uncertainty of the forecast being made; 2) adjusting the release so it is spread out over the entire month of May rather than having flows and the number of boaters peak on Memorial Day weekend; 3) a review of the implementation of the operating criteria so that Bureau of Reclamation does not have to so aggressively adjust release levels when operating criteria and inflows collude.

In this case, after cutting the release below 800 cfs and effectively ending the rafting season in early June, Bureau of Reclamation was forced to release between 600 to 800 cfs for three weeks in June because they couldn’t hold any more water in the reservoir. This ended up being “useless” flows for boaters, which would have been welcome to augment the low flows over Memorial Day weekend.