Rule curves might get a tweak

Duane Hicks

Can the 2000 rule curves be improved?
The International Rainy and Namakan Lakes Rule Curves Study Board has found evidence the rule curves pretty much have performed as expected.
But the board now is looking at two alternative options to “tweak” them, engineering advisor Matt DeWolfe reported during a progress update to the public last Wednesday night at the Fort Frances Public Library.
The study board was tasked in August, 2015 to make scientifically-supported recommendations to the International Joint Commission for modifying or retaining the 2000 Rainy and Namakan Lakes rule curves after reviewing a wide range of factors.
It has been working since then to review all available studies and monitoring data, as well as work with public advisory and resource advisory boards to weigh options.
During a shared vision planning session earlier last Wednesday over in International Falls, DeWolfe, who also is Canadian chair of the study board, said two preliminary alternatives based on the 2000 rule curve were presented:
•an adaptive rule curve which uses the La Niña forecast to reduce flood damages; and
•an environmental rule curve which adjusts the fall and winter levels to increase the percentage of muskrats that survive the winter.
DeWolfe said the first alternative would use climate data provided by the U.S. National Weather Service to determine if the rule curves should be altered each spring depending on La Niña and El Niño weather systems.
Looking back from 1950-2015, when La Niña conditions had developed and resulted in a cold winter with more snow on the ground, half of the time those winters preceded “a really high precipitation spring” and flooding conditions, he noted.
The other half of the time, it did not result in spring flood conditions but did not result in drought conditions, either.
On the reverse side, El Niño conditions tend to result in dry springs, although there always are exceptional years. You still can have flood years with a warm El Niño winter.
One of the challenges for the IJC is trying to make a management decision in March whether or not to lower lake levels to make room for a wet spring when it has no idea what’s coming, said DeWolfe.
“Snow pack does not predict a very high flow period,” he noted. “It certainly doesn’t help if you get rain on top of the snow.
“In 2014, in really, really big flood years, we’ve always had a heavy snow pack but a heavy snow pack doesn’t predict a flood,” DeWolfe stressed.
But the La Niña and El Niño forecasts may provide the IJC with at least “some inkling” of what precipitation may occur in the future—and whether lake levels should be adjusted ahead of time to accommodate it.
“There’s some important caveats, though,” warned DeWolfe. “Climate change is certainly an important one.
“We’re looking at 65 years of data where we have La Niña preceding a flood period half of the time,” he noted.
“Maybe that doesn’t happen in the future if the climate is shifting?”
DeWolfe said it also has been suggested that local residents participate in a group that gets together with the IJC’s water levels committee in March to look at the basin conditions, and discuss and formulate a plan each spring.
They would recommend, for example, if the lakes should be lowered if a spring is anticipated to have heavy rainfall.
The La Niña/El Niño forecast could play a part in this.
Meanwhile, the environmental rule curve is a potential adjustment that would be made to benefit the ecosystem, particularly muskrats.
“In years in this basin when flows aren’t too high or too low, the dam operators do a very good job of tracking within that target range of the rule curve,” said DeWolfe.
“If you’ve got good conditions year after year, like we did through the ’80s and ’90s most of the time, you’ve got pretty much the same track year after year,” he noted.
“The water level in the middle of July will be within a few inches of each other, July after July after July, which is great for some interests—navigational and some recreational preferences,” DeWolfe added.
“But in terms of an ecosystem, it’s nowhere near what you’d see in terms of natural lake levels and that has negative impacts for a lot of different ecological subjects.”
There’s concern right now, for instance, that muskrats get frozen out of their homes in the winter because the IJC currently drops the water levels after they established their houses.
The group also looked at altering water levels in the fall to help deter invasive cattails, but there was not enough public support for it.
Participants felt the alternative rule curves deserve more thorough investigation and might be part of their recommendation to the IJC.
The alternative rule curve options, which DeWolfe stressed are not mutually exclusive, will be discussed further in January.
What’s ahead?
Meanwhile, there’s still more work to do before the study group makes a final recommendation—and the IJC makes any final approval—about modifying or retaining the 2000 Rainy and Namakan Lakes rule curves.
In January, a draft decision workshop will be held, at which time they’ll look at the aforementioned alternatives and what the trade-offs are.
A final decision workshop then will be held in March.
The study board is due to submit the draft of its final report to the IJC on March 21.
Once the draft report goes out, there will be a public comment period where people can submit feedback online or during public hearings.
The study board then will take any input, revisit the report, and make necessary changes based on comments received.
A final report will be submitted to the IJC by the end of May.
IJC commissioners then will hold public hearings on the recommendations put forward so they can hear directly from people living in the basin before deciding whether to keep the 2000 rule curves, accept any of the study board’s recommendations, or make their own changes based on what they hear.
“We can’t guarantee anything at this point, or even when we finish the study, what the IJC will do,” stressed DeWolfe.
He added the best they can do is put forward a good case largely built on getting input from advisory groups and the public.