Transmountain water boosts dilution of mine drainage and benefits gamefish in the North Fork of the #SouthPlatte #ColoradoRiver #COriver

From The Fairplay Flume (Kelly Kirkpatrick):

Why, exactly, are the fish dying?

Fish kills in the North Fork of the South Platte River are occurring during low water flow periods that fail to dilute the toxicity of heavy metals such as iron, copper and aluminum. Contaminants in the form of heavy metals move downstream, originating primarily from Hall Valley and Geneva Creek mining operations.

When water flow is adequate, there is enough oxygen to negate the impact of the toxins. When water levels are inadequate, fish develop coatings on their gills as a natural self-defense mechanism to the toxins. That protective coating ultimately renders their gills inoperable.

When and why do water levels get too low?

Water flow in the river is dependent upon how much water is released from Dillon Reservoir through Roberts Tunnel, and those decisions are made almost exclusively by Denver Water.

When more water is needed within Denver Water service areas, the rate of the water passing through Roberts Tunnel is set to flow more freely. When water is not needed to serve the Denver Water service area, the flow from Roberts Tunnel is restricted, much to the detriment of the people, and the fish, in Park County.

Water flows can be naturally low in the river during certain seasons. This year, in mid-March, for example, snowmelt had not yet occurred and the river was in its customary state of low flow prior to the fast-approaching late-spring thaw.

An abundance of area-wide spring moisture, however, created a situation where Denver Water service areas enjoyed a surplus of water. Therefore, the flow from Roberts Tunnel and Dillon Reservoir was ceased on March 11 and remained so at least until this writing.

The predictable result was the most recent fish kill, which occurred March 11-15, because flows were simply not sufficient to combat ever-present toxic heavy metals related to mining. No information has been provided by Denver Water as to when the tunnel will be reopened.

Denver Water states its position

When The Flume recently requested a statement from Denver Water regarding flows in the river and operations of Roberts Tunnel, a response was received in timely fashion.

In direct response to whether or not Denver Water felt a moral obligation to residents in Park County related to ecological systems they have long controlled, and whether Denver Water should accept responsibility for maintaining minimal flow in the South Platte River for the environmental and economical benefit of the entire North Fork region, the following statement was submitted:

“We (Denver Water) understand the potential for impacts to the fishery when flows from the Roberts Tunnel are shut down, and certainly recognize and appreciate the effect on the angling community and local businesses and outfitters. Unfortunately, operation of the Roberts Tunnel is directed by legal obligations and decrees tied to Colorado water law and binding agreements with West Slope communities where the water from the tunnel originates.

“As you know, the flows from the Roberts Tunnel originate in water diverted from West Slope rivers and streams into Dillon Reservoir. Denver Water depends on this supply when snow pack within the Upper South Platte watershed is insufficient. However, since early March, portions of the Upper South Platte watershed have received more than four feet of snow and spring precipitation continues to be strong.

“Legally, water supplied through the Roberts Tunnel can only be accessed when water is needed in Denver Water’s service area. Further, any other uses for the water, including augmenting stream flows for aquatic life or recreation uses, are not allowed as a primary purpose for operating the tunnel.

“While we provide projections about how long Denver Water will deliver water through the tunnel, those are only estimates based on snow pack, reservoir storage and other system elements. Those projections can change as conditions change; as they did in late winter and early spring this year.”

Colorado transmountain diversions via the State Engineer’s office

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