Perhaps one of the most striking signs of the low snowpack and drought that has plagued Colorado this year can be found by driving by Green Mountain Reservoir in Grand County.

The reservoir, first filled in the 1940s, is at its lowest level since the 1960s, when it was drained for maintenance work.

Low snowpack is driving this summer’s low levels. The reservoir has dropped so far that people can cross it on foot without getting their feet wet.

But that’s proving to be a bit of an advantage as Northern Water is using that low level to make critical repairs to the reservoir that will save both time and money.

The spillway apron for the dam is 80 years old and in need of repair. Jeff Stahla, a spokesman for Northern Water, said those repairs were anticipated to start in two years, but opportunity came knocking with the low water level, so Northern Water and their contractor, Dietzler Construction, got to work.

The approach apron, which helps guide water over the spillway, is being repaired at a cost of about $1.25 million, equally split between Northern Water and the Bureau of Reclamation. That’s a savings of at least $2.5 million from what it would cost if the repairs were done a couple of years from now.

Northern Water, based near Berthoud, is one of the state’s largest water providers. It operates the Colorado-Big Thompson Project, which diverts water from the Western Slope to the Front Range and has done so since the 1940s.

The conservancy district built and operates several reservoirs west of the Continental Divide: Green Mountain; Ruedi, near Basalt, which provides water for the Arkansas River; and Wolford Mountain northeast of Kremmling, jointly operated with the Colorado River Water Conservation District and which provides water to the Windy Gap Reservoir, also in Grand County.

That Windy Gap Reservoir supplies water to Lake Granby, which then flows to the Front Range.

So how low is Green Mountain?

Its capacity is 154,645 acre-feet of water. One acre-foot is about 362,000 gallons or enough water to supply two families of four for a year.

According to data from the Bureau of Reclamation for Sept. 1, the reservoir currently holds 22,814 acre-feet of water, more than 8,000 acre-feet less than a month ago.

That current level puts the reservoir at 15% of its capacity.

The reservoir is currently at 7,842.6 feet above sea level. That’s down 14 feet from a month ago.

Dead pool for Green Mountain is 7,800 feet elevation.

As with many large reservoirs, Green Mountain does generate hydropower, so the potential for the reservoir to drop to its dead pool level, when it can no longer generate hydropower, is a concern.

When the reservoir fell below 7,870 feet in elevation, its usefulness for conservation purposes ended.

Another concern with such a low level is the water that supports endangered species programs.

Green Mountain is one of the sources of a “Historic Users Pool,” which annually provides 66,000 acre-feet of water to the Colorado River, primarily for use by farmers and ranchers in the 15-mile reach near Palisade.

That water also plays a critical role in protecting endangered fish in the 15-mile reach.

According to Aspen Journalism in May, “there won’t be any surplus water for fish in the Historic Users Pool, which is stored in Green Mountain Reservoir and is the largest source of water to potentially augment fish flows. A pool of water in Ruedi Reservoir that is available in four out of five years isn’t there, and the program could get only about 340 acre-feet from a pool in Wolford Reservoir upstream of Kremmling that typically has up to 6,000 acre-feet.”

Stahla told Colorado Politics the Bureau of Reclamation has capped water releases at six inches per day.

That’s because of the potential impact to the town of Heeney, population 74, that sits on the West Bank of the reservoir. If too much water is drawn from the reservoir, it raises the risk of landslides that could start deep below Heeney, Stahla explained.

The water table solidifies the bank against the hillside, he added.