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Lake Ontario: IJC report blames extreme precipitation, not Plan 2014, for 2017 flooding

Sat, Jun 23rd 2018 07:00 am
A view of Lake Ontario waters and the erosion impact from last year's record flooding. (Photo by Terry Duffy)
A view of Lake Ontario waters and the erosion impact from last year's record flooding. (Photo by Terry Duffy)
By Terry Duffy
Editor-in-Chief
Encouraging news for Lake Ontario property owners and recreational users as summer 2018 opens: Coming off a spring of near- or below-average precipitation, Lake Ontario's water levels are down significantly from 2017's record, historic highs, and have for the most part returned to their long-term near normal.
According to June 5 data by the International Lake Ontario-St. Lawrence River Board of the International Joint Commission, the U.S.-Canada body charged with regulating Great Lakes waters, Lake Ontario stood at 247.05 feet. While still considered above its long-term averages, the lake's June's levels are nearly 2 feet (23.2 inches) lower than 2017's record high water peak of last May.
"Lake Ontario has likely reached its seasonal peak this year, and while further rain events may cause lake levels to temporarily stabilize or rise slightly, water levels are expected to generally continue to fall over the summer months," the IJC board said.
In a detailed analysis released Thursday on the causes of last year's historically high water levels, severe flooding and erosion in the lake, the IJC board went on to place direct blame on the extreme precipitation events of last year and not on Plan 2014 - the IJC water regulation structure that many, particularly in the U.S., have faulted as the cause.
"Extreme weather and water supply conditions were the primary factors that caused Lake Ontario and St. Lawrence River water levels to rise to record-breaking levels last year," said the board in its 51-page report, titled "Observed Conditions & Regulated Outflows in 2017."
Expanding further, the report discussed the unusual weather patterns of last winter-spring, which combined with snowmelt went on to cause havoc throughout the Lake Ontario basin-St. Lawrence River areas in the months that followed.
"The record-high water levels experienced in 2017 can be attributed to a variety of factors, as well as timing and interaction, but simply put, the high water was mainly due to record precipitation received across the Lake Ontario and St. Lawrence River basin," the report said.
It continued: "From January through May of 2017, many locations recorded more precipitation than during the same five-month period of any previous year dating back to at least 1942, including Toronto, Ontario, and Rochester, New York, on the shores of Lake Ontario, as well as the cities of Ottawa, Ontario, and Montreal, Quebec, near the confluence of the Ottawa and St. Lawrence Rivers. The wet weather also extended upstream to the Lake Erie basin, where, for example, Buffalo, New York, recorded its second-highest January to May total since 1938. This increased the level of Lake Erie, and the amount of water entering Lake Ontario via the Niagara River.
"As a result, the combined total inflow of water to the Lake Ontario and St. Lawrence River system was well above average, and at times unprecedented. From January through March, the net total inflow to Lake Ontario was the 13th highest for this three-month period since records began in 1900. April and May were the wettest of all, and with Lake Erie also nearing its seasonal peak, the total inflows to Lake Ontario were even more severe. April 2017 saw the second-highest total inflow on record for this month, while total inflows set a new record-high for the month of May. In fact, inflows to Lake Ontario during April and May of 2017 were two of the four highest months recorded since 1900, and combined this was the wettest two-month period ever recorded for Lake Ontario. As a result, levels of Lake Ontario rose rapidly, setting new record-highs by the end of May, exceeding the highest levels recorded since at least 1918 when reliable records began.
"As this was occurring upstream, the watersheds of the Ottawa and St. Lawrence Rivers were experiencing similar conditions downstream. Record precipitation in April combined with snowmelt caused flow to rapidly increase in the Ottawa River. By April 20, flows in the Ottawa River reached a record peak for this date and were the highest Ottawa River flows since 1998, only to be exceeded at the start of May as two back-to-back storms further inundated the system resulting in the highest peak flow in the Ottawa River in over 100 years.
"Because the Ottawa River flows into the St. Lawrence River near Montreal, this meant the board was releasing water from a flooding Lake Ontario into a flooded St. Lawrence River."
The IJC Board went on to downplay any impact of Plan 2014 on last year's flooding. That measure, implemented in January 2017, regulates water levels and flows in the Lake Ontario basin as well as the upper St. Lawrence, and established a new set of rules to determine the outflows from Lake Ontario. It placed increased consideration to the impacted interests, both in the Lake Ontario basin as well as the St. Lawrence areas, in its determinations on regulating water flows. Plan 2014 replaced IJC Plan 1958-D, which had been in use since 1963.
In its explanation, the IJC board said, "It is clear that Plan 2014 did not cause, or meaningfully exacerbate, the flooding and associated damages that occurred in 2017. A review of the rules of Plan 2014 and how they responded to the hydrologic conditions that occurred, as well as the factors the board had to consider when it deviated from those rules, indicates that the outflows released in 2017 under the new regulation plan would have been very similar to those that would have been released had the board still been operating under the old regulation plan.
"Moreover, while the board had greater authority to deviate and release flows other than those that the rules of Plan 1958-D would have prescribed, it is unlikely that this greater authority would have changed the outcome in 2017 in any significant way. Essentially, the extreme weather and water supply conditions that occurred largely dictated the outflows that were released during 2017, and this would have been the case under either regulation plan."
In releasing the study, the IJC Board said it intended to "add clarity and transparency to how its outflow regulation under Plan 2014 took the needs of all interests into account and reduced the upstream and downstream impacts to the extent possible. ...
"While regulating Lake Ontario outflows can help reduce flood damages, it cannot prevent major floods from occurring under extreme water supply conditions. The board hopes this report will increase public understanding of that reality. To reduce future flood damages, shoreline communities must become more resilient, particularly since climate change increases the uncertainty regarding future high-water events and their frequency."

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