Day: June 11, 2016

Flows in upper Roaring Fork River could double with curtailed diversions

A little under 600 cfs of water flowing out of the east end of the Twin Lakes Tunnel on June 6, 2016. A similar amount of water could be heading west down Lincoln Creek and the Roaring Fork River next week if the Twin Lakes Reservoir and Canal Co. closes the tunnel due to constraints on its water rights.
A little under 600 cfs of water flowing out of the east end of the Twin Lakes Tunnel on June 6, 2016. A similar amount of water could be heading west down Lincoln Creek and the Roaring Fork River next week if the Twin Lakes Reservoir and Canal Co. closes the tunnel due to constraints on its water rights.
A graph showing the level of diversions through the Twin Lakes Tunnel so far in June 2016. The 618 cfs flowing through the tunnel could be turned back into the river within a week.
A graph showing the level of diversions through the Twin Lakes Tunnel so far in June 2016. The 618 cfs flowing through the tunnel could be turned back into the river within a week.

ASPEN (Brent Gardner-Smith) – The Twin Lakes Reservoir and Canal Co. has alerted Pitkin County officials that it soon intends to stop diverting about 600 cubic feet per second of water through the Twin Lakes Tunnel near Independence Pass.

The non-diversion of water from the headwaters of the Roaring Fork River, which could begin by midweek and last up to three weeks, could double forecasted flows in the Stillwater section of the Fork just east of Aspen, depending on weather and runoff levels. That may inundate the popular North Star Nature Preserve.

“We may see a couple of weeks or more where we are not taking anything through the tunnel, and hopefully that doesn’t cause too much flooding on that side,” said Kevin Lusk, a senior engineer with Colorado Springs Utilities and the president of the board of the Twin Lakes Reservoir and Canal Co.

The Roaring Fork, as measured at Stillwater Drive east of Aspen on a federal gauge, was flowing in the 500-to-750 cubic-feet-per-second (cfs) range on Friday.

Also on Friday, there was 618 cfs of water being diverted east through the Twin Lakes Tunnel and under the Continental Divide, bound for Front Range cities and fields near Ordway, in the lower Arkansas River basin.

The North Star Nature Preserve, with the Roaring Fork River still mostly within its banks, on Saturday, June 11, 2016. The view could change if th Twin Lakes Reservoir and Canal Co. turns back the 600 cfs it is diverting through the Twin Lakes Tunnel.
The North Star Nature Preserve, with the Roaring Fork River still mostly within its banks, on Saturday, June 11, 2016. The view could change if the Twin Lakes Reservoir and Canal Co. turns back the 600 cfs it is diverting through the Twin Lakes Tunnel.

Doubling the flow?

If Twin Lakes does turn off the diversion tunnel by midweek as expected, the Fork could be flowing in the 1,100-to-1,200 cfs range, instead of the 500-to-550 cfs range, as forecasted by the Colorado River Basin Forecast Center.

The current forecast, which assumes the Twin Lakes diversions are in place as usual, shows the Roaring Fork at Stillwater reaching a seasonal peak flow of 755 cfs today. Flows are then forecast to drop to the 500-to-550 cfs range by Wednesday. (The river actually beat the forecast and reached 773 cfs on Friday).

This would be the second straight year that Twin Lakes has stopped its diversions from the Roaring Fork headwaters due to plenty of water in the Arkansas basin.

Last year, Twin Lakes was diverting 528 cfs when it suddenly closed the tunnel on June 4.

A couple of days later, it diverted about 200 cfs for a brief time to try to reduce flooding of an old cabin along the river, and then, out of options, it left the tunnel closed until July 20.

A graph showing the levels of diversion through the Twin Lakes Tunnel in May, June and July of 2015.
A graph showing the levels of diversion through the Twin Lakes Tunnel in May, June and July of 2015.

Last year’s non-diversion of water by Twin Lakes helped push the Roaring Fork at Stillwater to a peak flow of 1,680 cfs on June 18.

The only minor damage caused in Pitkin County by last year’s high water was to the little cabin. And to the delight of paddlers on the Stillwater section of river, the high water also formed “Lake Northstar” on the North Star Nature Preserve.

A cabin dating to the mid-1960s in the Stillwater section of the Roaring Fork River was flooded in June 2015, with standing water in the living room and in a nearby art studio.
A cabin dating to the mid-1960s in the Stillwater section of the Roaring Fork River was flooded in June 2015, with standing water in the living room and in a nearby art studio.
A large portion of the meadow in the North Star nature preserve east of Aspen was flooded in June 2015, allowing boaters in the Stillwater section of the Roaring Fork River to expand their horizons.
A large portion of the meadow in the North Star nature preserve east of Aspen was flooded in June 2015, allowing boaters in the Stillwater section of the Roaring Fork River to expand their horizons.

Non-diversions rare

It’s rare for Twin Lakes to stop diverting water, but it has constraints in its water-right decrees that can, in wet years, force it to stop moving water from the West Slope.

Twin Lakes operates what is formally known as the Independence Pass Transmountain Diversion System. It gathers water from the Roaring Fork River and from Lost Man, Grizzly, Lincoln, New York, Brooklyn and Tabor creeks, and delivers the water to Grizzly Reservoir.

From Grizzly Reservoir, the water is sent through the 4-mile-long Twin Lakes Tunnel, under the Divide, into Lake Creek and down to Twin Lakes Reservoir, on the east side of Independence Pass.

The Twin Lakes Reservoir and Canal Co. is controlled by various municipal shareholders in the company, with Colorado Springs owning 55 percent of the shares, Pueblo 23 percent, Pueblo West 12 percent, and Aurora 5 percent. There are also other minority shareholders still using the water from the system for agriculture.

One constraint in Twin Lakes’ water rights, which date to 1936, is tied to the Colorado Canal, which diverts water from the lower Arkansas River under a relatively junior water right.

If the demands of the Colorado Canal can be met with “native” water from the Arkansas, then Twin Lakes cannot divert water from the West Slope to fill the canal.

This year, there is a lot of water running down the Arkansas, and so the canal does not need supplemental water from the West Slope, at least not yet.

The east end of the Twin Lakes Tunnel on June 6, 2016. The four-mile long tunnel brings water from Grizzly Reservoir to Lake Creek, Twin Lakes Reservoir, and on to Front Range cities and fields.
The east end of the Twin Lakes Tunnel on June 6, 2016. The four-mile long tunnel brings water from Grizzly Reservoir to Lake Creek, Twin Lakes Reservoir, and on to Front Range cities and fields.

Storage constraint

The other water-right constraint relates to how much water Twin Lakes can legally store in Twin Lakes Reservoir.

Once Twin Lakes, the company, has stored 54,452 acre-feet of water in Twin Lakes, the reservoir, the company has to stop diverting water from the Roaring Fork basin for storage.

Normally by the time Twin Lakes has reached its storage limit, the flow in the lower Arkansas has dropped and the Colorado Canal gets called out by senior diverters, so Twin Lakes can send supplemental water to the canal, allowing the Twin Lakes Tunnel to divert all summer.

But due to this year’s weather and snowpack, the constraints on Twin Lakes’ water rights have again come together, forcing the tunnel to be turned off as soon as the storage limit is reached, especially as the weather forecast suggests runoff into the Arkansas will remain high.

The Colorado Canal in March 2016.
The Colorado Canal in March 2016.

Timing uncertain

If cool and wet weather were to materialize over the next few days, however, cit ould delay when Twin Lakes reaches its storage limit and has to stop diverting. It could be midweek, or it could be next week.

And how long the tunnel stays closed depends on a range of factors, Lusk said, including weather, flows into the Arkansas, and the operation of Twin Lakes Reservoir.

Valerie MacDonald, Pitkin County emergency manager, said officials with Twin Lakes have done a much better job this year than last year in communicating about the likelihood of a non-diversion.

She also said local public safety officials are prepared to respond to high water and that concerned property owners can find information about flood readiness on the Pitkin County website.

Editor’s note: Aspen Journalism, the Aspen Daily News, and Coyote Gulch, are collaborating on the coverage of rivers and water. The Daily News published this story on Saturday, June 11, 2016.

A map of the Independence Pass Transmountain Diversion System, as submitted to Div. 5 Water Court by Twin Lakes Reservoir and Canal Co.
A map of the Independence Pass Transmountain Diversion System, as submitted to Div. 5 Water Court by Twin Lakes Reservoir and Canal Co.

Cambodia: Laser technology reveals cities concealed under the earth which would have made up the world’s largest empire in 12th century – The Guardian

Graphic via the Juan Chacon Free Software and Education Project here.
Graphic via the Juan Chacon Free Software and Education Project here.

Here’s a report from Lara Dunston writing for The Guardian. Click through to read the whole article and for the video. Here’s an excerpt:

Archaeologists in Cambodia have found multiple, previously undocumented medieval cities not far from the ancient temple city of Angkor Wat, the Guardian can reveal, in groundbreaking discoveries that promise to upend key assumptions about south-east Asia’s history.

The Australian archaeologist Dr Damian Evans, whose findings will be published in the Journal of Archaeological Science on Monday, will announce that cutting-edge airborne laser scanning technology has revealed multiple cities between 900 and 1,400 years old beneath the tropical forest floor, some of which rival the size of Cambodia’s capital, Phnom Penh.

Some experts believe that the recently analysed data – captured in 2015 during the most extensive airborne study ever undertaken by an archaeological project, covering 734 sq miles (1,901 sq km) – shows that the colossal, densely populated cities would have constituted the largest empire on earth at the time of its peak in the 12th century…

The new cities were found by firing lasers to the ground from a helicopter to produce extremely detailed imagery of the Earth’s surface. Evans said the airborne laser scanners had also identified large numbers of mysterious geometric patterns formed from earthen embankments, which could have been gardens…

[David Kyle], “It’s impossible not to be excited. It facilitates a paradigm shift in our comprehension of the complexity, size and the questions we can address.”

While the 2012 survey identified a sprawling, highly urbanised landscape at Greater Angkor, including rather “spectacularly” in the “downtown” area of the temple-city of Angkor Wat, the 2015 project has revealed a similar pattern of equally intense urbanism at remote archaeological ruins, including pre- and post-Angkorian sites.