New reservoir to give farmers a breather
REDMESA – In this arid corner of La Plata County, the trite observation that every drop of water counts is more than a cliché. It’s gospel.
It’s logical then that the dam under construction a mile or two south of here to hold back water against hard times is a popular project.
The water collected in Long Hollow Reservoir from Long Hollow Creek and Government Draw will supplement the often scant water from the La Plata River, half of which must be shared with New Mexico.
“We’re happy to see the project moving along so well,” Brice Lee, president of the sponsoring La Plata Water Conservancy District, said last week. “It’s been a tough year because we haven’t gotten the monsoons yet.”
Lee gets water from a ditch off the La Plata River for pasture and to irrigate hay. But he’s had only four days of water from his ditch so far this spring.
“It’s been pretty puny,” Lee said. “I don’t know if we’ll get more, but I didn’t have hay last year and probably won’t this year the way things are going.”
Hundreds of other irrigators who depend on La Plata River water are in dire straits.
Long Hollow Creek and Government Draw drain a basin of 43 square miles on the east side of Colorado Highway 140 about five miles north of the New Mexico line and about a half mile from the confluence of Long Hollow Creek and the La Plata River. The reservoir, expected to be completed this year, will have a capacity of 5,432 acre-feet and 160 surface acres.
No potable water will be available. Residents get household water from wells or truck it home.
During dam construction, water from Long Hollow Creek and Government Draw is contained by coffer dams and diverted to the reservoir outlet system, which was the first component built after initial excavation began in June 2012.
Now, drillers and grouters are the skilled workers of the moment, said Aaron Chubbuck, project manager for the Weeminuche Construction Authority. They’re drilling and filling with grout under pressure, holes as deep as 120 feet to create an impervious curtain or shield to prevent leakage.
The curtain extends to bedrock beneath the dam and protects the lateral reaches as well.
A clay core is the center of the earthen dam, which is 125 feet high with a span of 900 feet. Next to the core on the upstream side is a layer of granular rock fill, followed by a cap of riprap – large slabs rock or concrete that protects against erosion.
Next to the core downstream is a sand-based chimney filter and then tons of rock and earth as an anchor.
All the materials used in construction come from on-site sources, Chubbuck said.
Rick Ehat, who finished the Animas-La Plata Project on schedule and on budget after an earlier administration ran into construction and financial delays, is the construction engineer on Long Hollow.
The A-LP came out of a settlement of Native American water-right claims. Water comes from the Animas River.
Colorado and New Mexico share the water of the La Plata River under a 1922 agreement. Each state has unrestricted use of water from Dec. 1 to Feb. 15. But from then to Dec. 1, if the river is flowing at less than 100 cubic feet per second at the state line, Colorado must deliver one-half the flow at Hesperus to New Mexico.
Fulfilling the compact isn’t easy for several reasons:
The La Plata, which rises in the mountains north of U.S. Highway 160, doesn’t have abundant water even in its best years.
Water availability and the growing season don’t follow parallel paths. The bulk of the water – as 95 years of records show – is available from April 1 to July 1. Flow shoots from 50 cubic feet per second to 200 cfs then drops quickly to 50 cfs before trailing off. The growing season goes on much longer.
A porous river bed and vegetation siphon off water in the 31 river miles from Hesperus to the state line.
Lee said there are probably 15 major ditches off the La Plata River and many smaller ones. He estimated that 500 to 600 irrigators have a share of the flow, however small.
The cost of the project must come in at $18.6 million or less because there’s no additional funding in sight, Lee said. The source is $15 million – plus accrued interest – from what the state contributed for irrigation in the Animas-La Plata Project. The irrigation component was removed from the A-LP – a settlement of Native American water right claims – in the 1990s.
“The A-LP damaged ag here so we started working on Long Hollow about that time,” Lee said. “If we’d had a project like McPhee Reservoir in Montezuma County, which supports viable ag, we’d be years ahead of where we are now.”