A Dolores Basin snowpack that came in at half its normal level means McPhee Reservoir will not fill to capacity, and farmers may receive 20 percent less water this season.
On Thursday, Dolores Water Conservancy District managers estimated that full-service irrigators will have 17 inches of water per acre available for their crops, down from 22 inches per acre when McPhee is full.
The shortage also will impact Ute Farm and Ranch water supplies drawn from McPhee. Ute Farm and Ranch is estimated to take about a 20 percent cut, with delivery at 18,900 acre-feet, compared with 23,300 acre-feet when there is a full supply. The fishery pool reserved for habitat below the dam also will be impacted. The reserved fish pool, released from the dam over the year by Colorado Parks and Wildlife, dropped to 23,100 acre-feet from a supply of 29,300 acre-feet when the reservoir is full.
Municipal water supplies from McPhee serving Cortez and Towaoc do not share in the shortage and will receive full allocations. Because of the dry winter and spring, there will be no recreational whitewater release this year below the dam.
Carryover storage of 125,500 acre-feet – active supply left in the reservoir from last winter’s above-average snowpack – is helping to buffer this winter’s lack of moisture, officials said.
“We are living off last year’s carryover storage,” said Ken Curtis, an engineer with the water district.
The 2018 runoff forecast from the Dolores River into McPhee is comparable to the extremely dry years of 2013 and 2002, when farmers received just 6 to 7 inches per acre, a 72 percent shortage.
During an average winter, total runoff into the Dolores River from snowpack is 295,000 acre-feet. This year, models predict runoff of just 50,000 acre-feet.
“If that continues to drop, we may not get the 17 inches,” said Godwin Oliver, a farmer and board member of the Dolores Water Conservancy District.
Hurting this year’s McPhee supply is that there is no low-elevation snow. Feeders such as House and Beaver creeks are usually chock-full of rushing water this time of year, but they are now bone-dry. Dry soil conditions left over from the fall are also negatively impacting supply.
Limited snowpack remains above 10,000 feet, but it might be absorbed into the ground before making it into the river.
The water-supply prediction is based on snowpack measurements in the mountains and runoff modeling. It is an inexact science, so final supplies could rise or fall.
Variables such as warm or cold weather, soil moisture, wind, dust on snow, spring precipitation and fall monsoons impact the final amount of water supply in myriad ways.
Farmers are closely watching supply forecasts in order to plan for the season. The amount of available water determines how many acres they will farm and how much fertilizer, herbicide and seed they will buy.
“I’d rather shoot for low (water supply) and adjust up, than the other way,” Godwin said.
A main benefit of reservoirs is that they store water to get through dry years like this one, officials said.
“Overall, we are better off than 2013 and 2002,” said board member Don Schwindt.