Kim Fundingsland/MDN A father and son enjoy an afternoon of fishing on the Souris River near Minot’s water treatment plant. The Souris River will see additional flows soon as water being released from Lake Darling enters the city.

FOXHOLM – Lake Darling began releasing 150 cubic feet per second of water into the Souris River this past Monday morning. The water should be visible within the City of Minot as early as today.

The release comes at a time when Lake Darling is approximately two and one-half feet below its normal summer operating level and, without significant rainfall to replenish and recharge the lake, it is in increasing danger of a deadly fish kill this summer or perhaps into winter. But then, managing water during a drought is not without risk.

In the historic flood year of 2011 flows in the Souris River traveled much faster than anticipated. This year, in drought conditions, flow rates are again off the charts. This time, though, at the opposite end of what occurred in 2011. With conditions as historically dry as they are now, it is unknown territory when it comes to estimating flow rates, even amounts of water.

For example, a recent release of 30 cfs from Lake Darling barely made it to Minot and had virtually no impact on river readings downstream from the city. Speculation is that the water was absorbed by dry riverbank.

The water was being released with the intent of raising pool levels at J. Clark Salyer National Wildlife Refuge which, in turn, is responsible for releasing 20 cfs of water to Manitoba from June through October per International Agreement. Because the initial release of water never made it down river, the decision to increase releases from Lake Darling to 150 cfs was made.

“How much water will get here? We’ll just have to see,” said Kyle Flannery, Upham, project leader for the Souris River Refuges. “I’m not keen on releasing more water than I have to. I don’t know when this is going to end.”

Water levels are very low throughout the Souris River system. Recent heavy rains over portions of the drainage increased flows a bit in some locales, but only for a short period of time without resulting in a noticeable impact on river or lake levels. The effect of the drought is especially evident at J. Clark Salyer NWR which is located in one of the driest areas of the state.

“We are already in severe drought,” remarked Flannery. “We’re trying to move 10,000 acre feet of water from Lake Darling to benefit habitat at Salyer and so that we can provide 20 cfs to Manitoba. It’ll take about a month to move the water.”

“With the amount of water we’re estimating to send to J. Clark to meet Manitoba obligations it should drop Lake Darling about 14 inches,” said Tom Pabian, Upper Souris NWR mgr. “That’s provided Mother Nature doesn’t help us out.”

Lake Darling is a fairly shallow reservoir with an average depth of about 14 feet when at full summer operating level of 1,997 feet. Not this year, though. With current releases and expected evaporation of an inch a day, Lake Darling was at 1,594.5 feet Tuesday and could drop close to 1,592 feet yet this summer.

“About 1,592 becomes high risk for losing our fishery,” said Pabian. “But there’s a lot of factors involved there.”

Summer fish kills can occur when hot daytime temperature are followed by a calm night. The risk of a summer fish kill increases when water levels are low. Low water heading into freeze-up becomes problematic too if ice becomes thick, stays in place for longer than usual, or snowcover builds up on a lake. All those conditions can lead to lower levels of dissolved oxygen which is vital for fish survival.

There are varying levels of drought designation in the International Agreement. For the Souris River refuges imminent drought is reached when storage levels drop to 60,000 acre feet. Lake Darling is estimated to be about 85,000 acre feet today and will drop to about 75,000 acre feet in a month. At 40,000 acre feet the “severe” designation is reached and, according to the International Souris River Board, no further water need be sent to Manitoba.

“Of course, if we get rain then maybe we wouldn’t need more water from Lake Darling,” said Flannery.

The first two holding pools at J. Clark Salyer NWR have been all but dry this summer. Current estimates are that Pool 320 contains 813 acre feet of water and Pool 326 a mere 87 acre feet. Both pools have reached levels far below what triggers “severe” drought designation.