July/August 1997
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July/August 1997 |
by Frank Bevacqua
Due to heavy precipitation, high water conditions have prevailed this year in a number of watersheds of concern to the International Joint Commission. The Commission took emergency action in cases where it could provide relief to communities threatened by flooding and erosion. More information about water level conditions in several of these watersheds can be found on the World Wide Web, including the web sites mentioned in this article.
The past two winters brought heavier than average snowfall to the Great Lakes basin. For all of 1996, precipitation over the entire basin was 113 percent of average, the fifth highest year since 1900. Precipitation over the Great Lakes basin was above average in the first three months of 1997 and it appeared as though lakes Superior, Huron, Michigan and Erie could approach the record high levels set in 1986. Various Great Lakes jurisdictions distributed sandbags and advised homeowners to make sure their flood insurance was up to date.
Precipitation over the Great Lakes basin was below average in April and at average in May 1997, though the total for the year still remains above average. By early June, it appeared that lakes Superior, Michigan and Huron would not set record high levels, though Lake Erie was close to its record high level. While levels were extremely high, and high winds brought flooding to shoreline communities on a number of occassions, the damage so far this year fortunately has been less extensive compared to previous high water years.
For information on precipitation over the basin of each of the Great Lakes by month for the current year, visit http://sparky.nce.usace.army.mil/lev els/glbhyd.html. The daily levels of each of the Great Lakes during the current and previous month can be viewed at http://sparky.nce.usace.army.mil/levels/hmpglv.html.
The Commission regulates the outflow from Lake Superior with the assistance of its International Lake Superior Board of Control. The principal objective is to keep the level of Lake Superior in balance with the level of lakes Michigan and Huron so that each is in the same relative position within its range of fluctuation. At the same time, regulation tries to keep Lake Superior from going above or below certain levels specified in the Commission's orders of approval. When precipitation is high, all that can be achieved is to distribute the water among lakes Superior, Michigan and Huron so that one lake is not higher within its range than the other lakes. These will remain the objectives while portions of the compensating works, a control structure in the St. Marys River, are repaired this year. Operations were complicated when a tugboat sank and lodged under a gate of the compensating works until being removed five days later.
The Commission also regulates the outflow from Lake Ontario with the assistance of its International St. Lawrence River Board of Control. The Commission's orders of approval for the international hydropower project in the St. Lawrence River aim to maintain a four-foot range of levels on Lake Ontario. The orders also aim to provide a measure of protection to interests downstream of the project, including shoreline communities, navigation and hydropower. Emergency action taken by the Commission and its St. Lawrence Board since September 1996 removed nearly 60 centimeters (two feet) of water from Lake Ontario and protected downstream communities from extensive flooding. Significant shoreline erosion was reported at a number of locations along Lake Ontario.
Rainy and Namakan lakes are part of a chain of lakes along the Minnesota-Ontario portion of the international boundary. The lakes drain through the Rainy River into Lake of the Woods. Under the 1938 Rainy Lake Convention, the Commission has the authority to adopt measures of control with respect to the dams at the outflows of Rainy and Namakan lakes to avoid high or low water emergency conditions in the Rainy Lake watershed. In fulfilling these responsibilities, the Commission is assisted by its International Rainy Lake Board of Control.
Snowfall on the Rainy and Namakan basins was significantly above average during the winter of 1996-1997. On April 8, 1997, the Commission was informed of the threat of serious flooding in the town of Rainy River, Ontario. Due to spring runoff and ice jams at the mouth of Rainy River, levels in the river were high and some flooding was occurring already. By 6:30 p.m. on April 8, the Commission had directed that flows from Rainy Lake be reduced from 580 cubic meters per second to 140 cubic meters per second for three days. This action was taken after the Rainy Lake Board advised that it would not significantly increase the risk of exceeding the emergency level on Rainy Lake. The flow from Namakan Lake into Rainy Lake was to be reduced by the Rainy Lake Board.
By April 11, the river level at the town of Rainy Lake had dropped by about 90 centimeters (three feet) from its peak and had retreated from sandbagged areas in the town. The ice jam had moved several times, but was still not likely to clear from the river for some time. However, several channels had eroded through the blockage allowing more flow through the river. While the levels of Rainy and Namakan lakes had both gone above the bands prescribed in the Commission's orders, colder temperatures in the basin brought significant declines in runoff to the lakes. The Rainy Lake Board increased the outflows and from both lakes and emergency conditions, as defined in the orders, were avoided.
The Red River of the North flows between Minnesota and the Dakotas into Manitoba, where it empties into Lake Winnipeg. The Commission monitors water quality conditions in the Red River with the help of its International Red River Water Pollution Board. Though it has no responsibility for managing water levels and flows, the Commission stays informed of these conditions through its International Souris-Red Rivers Engineering Board.
Following record amounts of snowfall, April temperatures in the Red River basin rose from an average of minus 13 degrees to 14 degrees Celsius (9 degrees to 58 degrees Fahrenheit) in ten days, creating vast amounts of runoff. Flood crests broke records all along the Red River. Levees in North Dakota built by volunteers and local and state agencies held at Fargo and Whapeton, but Grand Forks was devastated by flooding. Over 50,000 residents were evacuated in the North Dakota portionof the Red River basin.
When flood waters reached Manitoba, 28,000 people were evacuated. There was major damage outside Winnipeg, but the floodway and diking efforts saved the city from a catastrophe. Over 8,000 Canadian Armed Forces personnel participated in the flood-fighting effort and ring dikes built around eight "island communities" kept these communities dry through the flood. For more information, visit http://www.gov.mb.ca/flood/index.html.
Devils Lake is part of a chain of lakes located in a closed basin in North Dakota. While the Commission has no responsibility for managing levels and flows in this system, it stays informed of conditions through its International Souris-Red Rivers Engineering Board.
Devils Lake has fluctuated about 12.5 meters (41 feet) from its last record high in 1867 to its record low in 1940. Having no outlet, Devils Lake can rise sharply when precipitation exceeds evaporation for sustained periods. It is now higher than it has been since records have been kept.
Since 1993, when Devils Lake covered 18,200 hectares (45,000 acres), water levels have risen steadily. By mid-summer of this year, the lake is projected to cover 42,500 hectares (105,000 acres). The state has spent nearly $35 million to raise and upgrade roads near Devils Lake and some have been closed because of flooding.
If Devils Lake were to rise another 4.5 meters (15 feet), it would drain through Stump Lake into the Sheyenne River and would no longer be a closed basin.
Heavy rain and snowpack runoff throughout British Columbia raised water levels in Okanagan Lake and Kootenay Lake basins in early June 1997. The Commission has established rules for the operation of dams in both basins that can raise water levels across the international boundary and oversees these projects with the assistance of its International Osoyoos Lake Board of Control and International Kootenay Lake Board of Control.
Flooding washed out a section of highway near Kootenay Lake and closed roads near the international boundary. The Province of British Columbia advised people in the Okanagan Valley to continue sandbagging because of the large snowpack and heavy rains. People were sandbagging throughout the valley from Vernon south to Osoyoos, British Columbia.
Frank Bevacqua is the public information officer at the International Joint Commission's Washington office.
Sommaire
Sous l'effet des précipitations abondantes, le niveau des eaux a monté cette année dans de nombreux bassins hydrographiques dont se préoccupe la Commission mixte internationale. Celle-ci a pris des mesures d'urgence dans les cas où elle pouvait venir en aide aux collectivités menacées par les crues et l'érosion.
Revised: July 7, 1997
Maintained by Kevin McGunagle,
mcgunaglek@ijc.wincom.net