LAKE DARLING DAM, N.D. – The 5 to 7 inches of rain that fell over vast plains of southern Saskatchewan and concentrated in the tiny Souris River last summer was the cause of the worst flood the Minot area had ever seen.

A quarter of the population of the state’s fourth-largest city evacuated, and thousands of properties were damaged.

In Kelly Hogan’s mind, though, it might have been a whole lot worse.

“What if 5 to 7 inches hit Kenmare? It would’ve all come down the Des Lacs,” he said as he gave a tour of the dam on a sunny day last August, less than two months after the flood.

The U.S. Fish and Wildlife manager oversees the wildlife refuge complex that includes this dam on the Souris River, the last in a series of dams up and down the basin that serves as the Minot area’s flood protection system.

Kenmare is west of here on the Des Lacs River, which drains into the Souris downstream of all the dams but just upstream of Minot. What Hogan meant is, if torrential rain had fallen there and not in Canada, none of it would’ve been held back by dams and all of it would’ve poured into Minot.

That happened in summer 2009, though there wasn’t quite as much rain.

Lake Darling was low because the spring runoff that year didn’t amount to much, Hogan said. There was plenty of flood storage available, he said, but it wasn’t used at all.

“It’s not how much rain falls but where the rain falls,” he said. “It all plays into how predictable the situation is – or is not, I guess I should say.”

But rain is now considered as much a threat as spring snowmelt, the cause of most floods throughout the basin’s history. So as unpredictable as rain can be, the state of North Dakota is working with the province of Saskatchewan to work it into the operations of the basin’s flood protection system.

It’s also mulling the buildup of existing dams, including Lake Darling Dam and the dam on the Des Lacs, and a dike system in the Minot area. Just about every option that could be on the table appears to be on the table to prevent what happened in 2011 from happening again.

Making sacrifices
A big push now is in Saskatchewan.
Gov. Jack Dalrymple and Sen. John Hoeven, R-N.D., were there a few weeks ago to talk with Premier Brad Wall, and they came away with a general agreement on a few key issues.

One of those key issues is the inclusion of rainfall in the operating plan of Rafferty and Alameda dams in Saskatchewan. The plan now calls for the dams to reduce the water they hold to account for snowmelt in the spring but not so much for rain in the summer.

North Dakota and Saskatchewan officials also agreed to study increasing the flow of water released from the dams, provide real-time data from rain gauges in Saskatchewan and, in general, be more “flexible and aggressive” during flood events, said Jeff Zent, Dalrymple’s spokesman.

The problem last summer was the dams had been drawn down to deal with a big snowmelt, but they weren’t drawn down enough for the torrential rain that fell. Simply put, the amount of rain that flowed into the dams was many times more than they could contain.

Changing the plan, though, may require the United States to make some sacrifices.

State Engineer Todd Sando, who will be involved in the negotiations, acknowledged that the unpredictability of rain will be a challenge to tackle, especially when the dams also serve double duty storing water in case of droughts.

In other words, if the dams release water to prepare for torrential rain and the rain doesn’t fall or doesn’t fall where it’s expected, there will be less water going into the next year. And if the next year is a dry year, and perhaps the year after that, water will suddenly become much more valuable.

Preserving that valuable resource was the main reason Saskatchewan built the dams in the first place. The 1989 U.S.-Canada agreement, which the dams operate under, lays out not just how the two countries will fight flooding but also how they will share water.

Sando said the agreement already requires the United States to give up its share of the water in some situations. It’s not out of the question that to get rain included in the operating plan, the United States would have to give up more water, he said, though that could bring on other problems.

Inadequate tools
Kelly Hogan can appreciate the capriciousness of rain.

Suppose it rains on a Friday night on that hill over there, he said. The next day, he’s looking at a rain gauge that says 3 inches, he said, but that’s still not enough information to know how it’ll affect his stretch of the river.

“I don’t know how extensive that rain was. I don’t have a gauge every square mile,” he said. “The way I’m going to know is when that rain and all the rain around it hits a point on a stream. So that may be 24 hours. It may be, in the case of a flash flood, six hours.

Depending how much sinuosity is in a stream, it may be four to five days. But you can’t grasp how that rain really affected an area until it hits that gauging station. There just aren’t enough rain gauges in the world.”

The situation isn’t much different in Saskatchewan, though there are fewer rain gauges for a given area.

But it’s not rain gauges that’s really needed there, according to Doug Johnson, a Saskatchewan Watershed Authority official who oversees several dams, including the Souris basin’s Rafferty and Alameda dams. What’s needed is better weather radar.

Weather radar gives water management officials a sense of the water content in a given cloud formation and if rain is falling. Rain gauges and stream flow gauges are used to calibrate the radar data so officials can connect a given radar pattern with a certain amount of rainfall.

Johnson said when he looks at radar images from the National Weather Service office in Bismarck, which doesn’t go very far in Canada, he sees things that he can’t see in Environment Canada’s radars, such as how much rain is falling, how hard it’s falling and how much has fallen.

In Canada, he said, a lot of that has to be figured out manually, and it’s a huge amount of information to calculate during a flood emergency. The system has worked out fine for years when summer rains weren’t so threatening, he said.

Ready for summer
But changing the dams’ operating plan won’t really be enough to fend off another flood of the same magnitude as summer 2011.

Hogan said there was enough water to fill Lake Darling 10 times, while Johnson said Rafferty Dam, which has the largest reservoir of all the dams, would’ve filled two to three times.

And the dams would’ve had to be empty to start with.

Sando, like other water management officials involved in the flood fight, said that with the dams as they are, the flood was inevitable. “Everything was done that could possibly be done.”
He said changes to the operating plan would be more useful for fighting major floods that are not as big as the one in 2011.

To fight the really big one, the state is at work designing a massive system of dikes and diversion for the Minot area. It’s also mulling a larger flood control system for the entire North Dakota portion of the Souris basin and adding capacity to various dams in the basin.

Sando said there have been very early discussions about raising the Rafferty, Alameda, Lake Darling and Boundary dams, and there could be talk of raising the dam on the Des Lacs as well.

Boundary Dam is on Long Creek, a tributary of the Souris, but its storage is mostly dedicated to the SaskPower power plant there.

But Sando said all of that could take a long time. Changes to the operating plan, for example, must include not just the state and provincial governments but federal agencies in both countries, he said. “I can see it taking years to make some of those changes.”

In the meantime, he said, officials will simply have to do what they can to make more room in the reservoirs in case of rain. The goal this year, he said, is to have maximum flood storage available before the start of this summer, something flood fighters didn’t have in summer 2011.

Tu-Uyen Tran reports for the Grand Forks Herald.