South Platte Roundtable meeting recap

Illustration shows water availability, in blue circles, compared with demand at various places along the South Platte River. The yellow area is the study area. (Illustration by Stantec).

From The Greeley Tribune (Tyler Silvy):

A yearlong study centered on a decades-long trend of Colorado sending too much water to Nebraska via the South Platte River yielded dozens of potential storage projects.

But high costs, potential environmental impacts, and bureaucratic and regulatory hurdles could doom the road ahead for any of those possibilities, according to a study presented Tuesday night at the South Platte Basin Roundtable meeting in Longmont.

Further, even if several of the identified projects happen, they would barely put a dent in what’s expected to be a Front Range water needs gap of 500,000 acre feet per year.

The $200,000 study, ordered by the Colorado State Legislature and paid for by the Colorado Water Conservation Board, looked at the South Platte from Greeley to the state line and identifyed potential storage solutions along the way.

Putting any of those solutions — with costs estimates ranging from $190 million to $1 billion — to work most likely will take more time, money and study…

Consultants from Stantec Consulting Services and Leonard Rice Engineers completed the study in December and have toured the state making presentations. The Legislature has yet to get a presentation, but here are the key points legislators will hear:

A large amount of water is physically and legally available but only during wet years and during short periods.

Mainstream options have the most benefit but likely are not permittable and have significant social impacts.

Many off-channel options appear to be feasible and could be combined in different concepts.

Even multiple projects won’t make a big dent in the supply gap.

One reason for the lack of impact is how the South Platte works. When farmers divert water from the South Platte to irrigate crops, some of that water soaks underground and slowly moves back to the river. That’s called a return flow, and return flows feed the South Platte to allow it to flow long after snowmelt water is gone for the season.

That’s why the Sterling No. 1 ditch can completely dry out the river with a diversion and then a mile downriver it’s flowing again.

That’s why the best possible place for a reservoir would be near the Colorado-Nebraska border, and the best solution for keeping as much water as possible — a mainstream reservoir — is the solution that likely never will happen.

A mainstream reservoir along the South Platte essentially would be a lake on the South Platte, with the western portion feeding into the lake and the eastern portion running when the lake releases water.

Water experts agree that would be nearly impossible to get approved.

But the consultants did identify storage options away from the river, including old gravel pits.

Still, building ditches or pipes to fill those gravel pits would prove costly.

The consultants also talked about the 2013 flood and high flows in 2015, which ended up sending 1.9 million acre feet of water to Nebraska — exponentially more water than Nebraska is entitled to via the 1923 compact with Colorado.

But managing or diverting water during a flood event like that would take technology water experts said just doesn’t exist. Instead, ditch companies did everything they could to keep the flood water out of their ditches, lest they get damaged by the torrent.

Groundwater storage also was touched on, but concerns were raised about water losses and the co-mingling of other water rights. Once the water flows under another landowner’s property, for example, they would have the right to pump that water to irrigate crops.

The conversation circled back to the reason for the study. Essentially, lawmakers on the Western Slope long have pointed to the excess water the Front Range sends to Nebraska. Rather than divert more water from the Western Slope, the argument goes, Front Range farmers and municipalities need to figure out how to keep what they have.

Mike Schimmin, a water rights attorney on the roundtable, said his fear is the study will reinforce those feelings and that people will ignore the high cost to capture the extra water.

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