Colorado Division of Water Resources

According to a November Durango Herald article, an experiment that started this summer could become half of a solution to make sure New Mexico receives its share of La Plata River water and help Colorado irrigators at the same time. “There’s never enough water,” said Rege Leach, Colorado Division of Water Resources engineer in Durango. “Historically, we’ve had to shut off Colorado ditches so many times to satisfy our compact with New Mexico.” According to the agreement, Colorado has to provide New Mexico half the water in the La Plata River--as measured at Hesperus--from Feb. 15 to Dec. 1 whenever the flow at the state line is less than 100 cubic feet a second. During the remainder of the time, water delivery to New Mexico isn’t required.
Spotty delivery occurs because the porous bed of the La Plata River easily can hijack more than half the water in the 30 river miles to the state line, Leach said. Riparian vegetation sucks up a large share, too. “It’s particularly difficult when the flow at Hesperus is 20 cubic feet a second or less,” Leach said. “If there’s 20 cfs at Hesperus, not even half gets to New Mexico--and that’s with no use in Colorado.”
In the summer, Leach and his engineers came up with the idea of diverting La Plata River water through the La Plata and Cherry Creek Ditch west to Cherry Creek, which flows into the river near Marvel about nine miles north of the state line. The detour, created by constructing a barrier of baseball-sized rocks in the river south of the ditch heading, skirts 20 river miles in which water disappears into the porous river bed. The bed of Cherry Creek has a more impervious geological composition. “The diversion allowed 80 to 90 percent of the water diverted into Cherry Creek to reach the state line,” Leach said. “It helped us meet our obligation to New Mexico.”
It should be noted, however, that there are still some unanswered issues and questions related to this strategy—especially in regard to how this approach may impact existing water rights. That is one reason why the La Plata Water Conservancy District requested funds from the Statewide Water Supply Reserve Account to study the impacts of alternative delivery methods such as this to meet the New Mexico Compact.