Grand Lake pumping resumes |

Grand Lake pumping resumes

Tonya Bina
Grand Lake, CO Colorado
Byron Hetzler/Sky-Hi NewsAbove, the west end of Grand Lake is seen on August 30, after a rare summer with no water being pumped through it from Shadow Mountain Reservoir.

Pumping Colorado-Big Thompson water reserves to the northern Front Range resumed Sept. 7 after a long period of no pumping.

Not long after the pumping resumed, observers of natural Grand Lake started noticing a difference in water clarity in the lake and in the connecting channel.

Anecdotally, many said the lake was the clearest they’d seen in decades during the rare period from mid-May to Sept. 7 when there was no pumping through Grand Lake. Pumping ceased due to heavy runoff this spring and early summer.

In the shallow, “crystal clear” connecting channel of Grand Lake and Shadow Mountain Reservoir, “The day after they started pumping, you couldn’t see the bottom,” said Watershed Program Manager Ben Carver, of the Grand County Water Information Network.

Secchi disc measurements back up observances. A Secchi disc is a water-clarity tool, a spindle of measuring tape with a black and white “Frisbee” attached to it. Lowered into the water, the tool measures the depth of clarity.

The Water Information Network’s paid field technician has been sampling clarity at 14 sites of Grand Lake three times per week this summer. In mid-July, the measurements averaged around 20 feet (6.25 meters).

On Sept. 10, three days after pumping resumed, the clarity on Grand Lake had been cut nearly in half to an average 11 feet (3.25 meters).

The channel became “a bottleneck for all the algae coming into Grand Lake” from shallow Shadow Mountain Reservoir, Carver said.

The aim of the Grand County Water Information Network, Carver said, is to provide accurate water data to stakeholders such as the Bureau of Reclamation, the Northern Colorado Water Conservancy District and Grand County, so that “this data gets used in some sort of policy-making tool” – for the “betterment of the lake,” he said.

Tonya Bina can be reached at 970-887-3334 ext. 19603

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