A minor boost of snowfall in April helped to stave off more shortages for local farmers who rely on McPhee Reservoir, water officials said during a meeting Monday.
As of this week, the forecast is still for full-service farmers to receive about 17 inches per acre, said Ken Curtis, of the Dolores Water Conservancy District, which manages the reservoir.
But the final runoff amount will not be known until June, and it will be impacted in coming weeks by variables such as wind, precipitation, dust on snow and soil moisture. Overall, the spring runoff into McPhee is dismal because of a winter with barely 50 percent of average snowpack, Curtis said.
It is thought that dry mountain soils from a dry fall are absorbing a lot of the water before it makes it to the river. According to the U.S. Drought Monitor, Southwest Colorado is in an exceptional drought, the most severe of five categories.
When the reservoir fills during more average winters, farmers typically receive a full allocation of 22 inches per acre, enough for three cuttings of alfalfa.
But significant carryover water from the previous winter’s above-average snowpack is saving farmers this year, Curtis said. “As far as runoff, we are getting close to the project’s worst year in 2002, but the difference this year is we have good carryover,” he said.
Based on 30-year runoff data, average McPhee inflow is 295,000 acre-feet of water from the Dolores River Basin from April through July.
This year, it is expected to be 62,000 acre-feet, or 21 percent of normal. In 2002, the reservoir received just 45,000 acre-feet, and farmers suffered more drastic shortages, receiving less than 50 percent allocation.
For boaters, there will be no whitewater release below McPhee dam. Also, the Dolores River above McPhee will not run as high or as long this year.
Peak flows from Rico to Dolores are coming early, and are not expected to reach more than 1,000 cubic feet per second, down from more typical peak flows of 2,000-2,500 cfs. Currently the river is running at 700 cfs at Dolores, but boatable flows are expected to end by before early June, instead of in late June or early July during more average years.
The next chance for substantial moisture in Southwest Colorado is the monsoon season of July through September, when summer monsoons typically draw up subtropical moisture from Mexico.
“Next year’s supply will depend slightly on monsoons later this summer and mostly on next winter’s snowpack,” Curtis said. “Ending the 2018 water year with little to no carryover increases the risk of a deeper project shortage next 2019 irrigation season.”
Montezuma Valley Irrigation has more senior rights than McPhee Reservoir, including a direct flow right on the Dolores River up to 700 cfs. The private company stores water in Groundhog, Narraquinnep and McPhee reservoirs and closely monitors water supplies to determine potential impacts to customers.
A recent court case that upheld a new 900 cfs in-stream flow right on the lower Dolores River from April 15 to June 15 below the San Miguel confluence does not impact McPhee Reservoir, officials said.
The in-stream flow rights are junior to McPhee Reservoir’s more senior rights so they have no impact on the local water supply. Decreed by the state for environmental purposes, the new Dolores River in-stream flows are only available when snowpack produces sufficient natural runoff to provide the 900 cfs.