No easy way to manage high water levels

High water levels were the big draw for local residents at yesterday evening’s joint annual public meeting of the International Rainy Lake Board of Control and the International Rainy River Water Pollution Board.
“It’s not really new news. You’ve seen, living here and experiencing it everyday,” said the IRLBC’s interim co-chair, Rick Walden, as he spoke to the dozens present at the Rendez-Vous on the reasons why waters have been so high this year.
“There’s only so much outflow that can be discharged, so when the input amount is exceeding the output capabilities through the dam and the upper river, then the inevitable result is the lake is going to end up higher than the lake residents would prefer,” said Walden. That’s exactly what has happened this year, he said, as the inflow level of water into the system was caused by not just an increase in rainfall, but the cooler weather the area has experienced.
“We have to remember how cool it was, for how long it was and the amount of water that the trees use up and that the evaporation uses up, is really tremendous,” explained Dr. Bill Darby of the IRRW, who was also there to help answer questions and concerns residents had over the high water levels.
“The other side of the coin, of course, is that this water has to go somewhere and where’s it going?” said Walden. “Downstream, most immediately impacting on the Rainy River and ultimately Lake of the Woods and Winnipeg River, right into the province of Manitoba.”
The increased inflow is not just affecting Rainy Lake, but also Namakan, the upper lakes, and Lac La Croix, which also means additional water having to move downstream from those areas as well, he said.
All this extra water is what many residents came to the meeting with concerns about the waters being increasingly unsafe, property damage, and damage to the natural environment.
But solving the high water levels on the lake is not a simple matter of opening up more gates, said Walden, explaining to those present basics with how hydraulics and the dam system works. “It’s not the number of gates open, at any particular time that counts … it’s how much water you can get out,” he said. To properly function, the dams need an higher water levels to push water out into other areas, levels that didn’t exist back in the spring and early summer.
As well, many lakes and rivers, such as at Pither’s Point have natural constraints that hold the water in until it gets to a certain level, explained Ed Eaton, one of the Engineering Advisors representing the American side of the IRLBC.
Adjusting how water levels are managed through would also be easier if the input levels were continually tending towards either the wetter or drier side, said Walden. But when inflow data is analyzed, within the past years there has been almost as many significant dry events as there has been wet events.
“There’s an interesting pattern in terms of rainfall,” said Walden as he presented inflow charts tracking inflow throughout the past few years, “If you look at week by week rainfall through the spring and early summer you see a kind of pattern, kind of a week on, week off. You have a significant amount of rainfall one week and inflows would be picking up again, and then you’d have virtually no rainfall for the next week and then inflows would start to flatten off in a couple cases even start to decline, lake levels would flatten off and then the next week back again to rain. So it just repeated this a number of times and eventually the inflows exceeded the outflow capacity and you got those high lake levels and high river flows that we’ve had in more recent years.”
“You can’t foresee what’s coming in. If for instance we knew that conditions were always tending to be wetter, then yes, [you] operate lower and you have more buffer space. But the problem is when you’re having both wetter and dryer, which buffer do you go for to allow for flood conditions or to allow for drought conditions? That’s the challenge.”
Comparatively, for the three months of May, June and July, the 2008 inflow rate was 884 m3/s (31,220 ft3/s), double the 30 year median amount calculated from the previous 30 years of 472 m3/s (16,670 ft3.s).
Yet the lake level has been higher in the recent past, such as in 2001 and 2002. Alongside that, 2006 and early 2007 were one of the driest periods the basin has experienced. It’s a trend of variable conditions going to different extremes on both sides, said Warden, a trend that is occurring more frequently compared to what was experienced during the 1980s and 90s. It’s also a trend associated with climate change, he added.
While weather conditions were monitored during the past year, said Warden, but there was no indication that there was going to be such an extremely wet season that would affect the inflow the way it did, and give them a chance to work to lower the water levels.
“Hindsight yes, it’s easy, you see what eventually came in, but at that time you don’t have that information you deal with what you do have,” he said.
They have theoretically calculated what regulation could be done for this basin area if they had access to the perfect forecast, said Walden, and to make a significant improvement to the lake level regulation, they would need to know exactly what quantity of inflow to expect at least six weeks into the future.
“Now clearly, we’re nowhere close to that,” he said.
“To deal with this water that came in this year you would have had to start way back months ago digging a big hole in that reservoir and creating a big space for it, and there’s no way you can take that chance because if that water doesn’t materialize then were are you going to be?” he said.
“The bottom line is, that as a society when we’re talking about nature, we’re kind of like a mouse with an elephant,” said Darby. “Nature has such a powerful influence and we only have so much control.”