Section 5: Impacts on Various Interests
5.1 General [top of page]
High water levels generally benefit municipal water users, shipping, hydro-electric generation, and recreational boaters. They negatively impact riparian owners by overtopping fixed docks or flooding buildings close to the water’s edge. In addition, shoreline erosion rates are often greater with higher water levels, and shoreline protection structures can be damaged with extreme high water levels. Wetlands extend further inland with higher water and are inundated to greater depths, which is beneficial from time to time. Periodic high water levels are necessary to sustain wetland productivity and health.
Low water levels impact municipal users as the water intakes may be above the water surface or affected by warmer and poorer quality water. Low water levels result in less water available for dilution of municipal waste water, or increased cost for treatment. Shipping and boaters are adversely affected by low water as channels are shallower. Ships may need to lighten their load to decrease the draft and recreational boaters may find that docks or launches do not extend sufficiently far. Hydro-electric generation is affected by lower available head or lower flows.
Low water levels benefit riparian owners whose docks may be short and low or who have buildings too close to the water’s edge. Erosion rates generally decrease with lower water levels.
Periodic low summer water levels can also result in positive environmental benefits. Low water levels expose more beach and mudflats. Additionally, wetland vegetation may extend further into the lake and river. Wetland dewatering encourages dormant aquatic seed bed germination benefiting wetland plant species and biodiversity.
Although Lake Ontario is to be regulated above 74.15 m (243.3 ft) during the navigation season and below 75.37 m (247.3 ft, both monthly means) there is no single critical low or high water level at which it can be said that "adverse impacts" occur in the system. The level of harm experienced by a user of the system greatly depends on the location and the usage and sometimes the time of the year The IJC and the Board are aware that various sectors in the system may be impacted as levels in Lake Ontario and the St. Lawrence River vary, even within their target ranges.
Shoreline communities can help the ISLRBC by communicating with us so that we understand your situation and concerns. More importantly, shoreline communities can help themselves by becoming better informed about coastal hazards and taking action to reduce their risks to such hazards, particularly through incorporating risk reduction measures into shoreline revitalization efforts and long-term planning of coastal zone uses.
Prior to the construction of the Moses-Saunders hydropower dam, the Long Sault Dam, and the associated protection structures, the St. Lawrence River upstream of the project was much narrower, containing fast-moving water and rapids, and was subject to ice jams and associated flooding. Construction of the seaway and power project stabilized flows and created Lake St. Lawrence, which is the large headwater pond upstream of the Moses-Saunders dam. The wider river flooded some historic villages and farms on both sides of the river. People who lost their homes had to relocate and many homes were moved to new sites upland. The projects also allowed for the growth of recreational boating and associated businesses in this area. Without the Moses-Saunders project and associated regulation, much of the St. Lawrence River between Ogdensburg and Massena, N.Y. would not be navigable for commercial or recreational vessels - except for canoes, kayaks, and rafts.
As water levels affect many interests, perhaps one of yours, the Board has many ways to communicate water levels in the system. The data page of our website indicates current and recent levels and allows users to subscribe to a list-serve for announcements. The publications page lists news releases. The Board posts weekly updates of levels and flows (In the U.S., the number is 1-800-883-6390, and in Canada the numbers are 1-800-215-8794 (English) and 1-800-215-9173 (French), or visit the board website.
The Board encourages everyone to be aware of water levels and to be prepared to live within the range of levels specified in the Orders of Approval. For Lake Ontario, the upper limit for monthly mean levels is 75.37 m (247.3 ft) and the lower limit (from April to December) is 74.15 m (243.3 ft), a range of 1.22 m (4 ft). Levels on the river tend to vary more widely.
5.2 Domestic Water Supplies and Sanitary Uses [top of page]
High water levels can threaten domestic water supplies and sanitary uses. These consist of flooding and backup of sanitary sewer lines, flooding and contamination of freshwater storage wells, and under very high levels or during storm events, possible flooding of freshwater intake pumping facilities.
Very low water level conditions may affect shore wells and municipal and industrial water intakes on the St. Lawrence River and along the entire Lake Ontario shoreline. Such impacts can be avoided through proper design of such facilities with anticipation of the entire range of Lake Ontario levels and flows prescribed by the Orders of Approval and those that occur on the St. Lawrence River.
5.3 Commercial Navigation [top of page]
The construction of the Seaway and power project opened the Great Lakes to ocean-going navigation. Outflows exceeding design limits in the regulation plan can result in severe water velocities and cross-currents in the river, which can occur at key points such as at entrances to navigation locks. In addition, very high flows at the Moses-Saunders hydropower dam reduce the available draft on Lake St. Lawrence, immediately above the dam, due to a drawdown effect at the dam and immediately upstream.
By contrast, very low outflows can result in extremely low levels in downstream areas of the Seaway and at Montréal Harbour, limiting the ability of vessels to transit the channels and/or approach docks. Under certain conditions, shippers may have to lighten their vessels, forcing them to either leave cargo behind or increase the number of transits necessary.
Yes. While high water levels on Lake Ontario can produce benefits for navigation, they often mean higher flows in the St. Lawrence River, which can have negative impacts. For example, higher flows can produce cross-currents that cause difficulty in controlling the vessels. Low levels can also be hazardous to navigation and can result in ship groundings. Shippers may have to lighten their vessels, forcing them to either leave cargo behind or increase the number of transits necessary.
The Commission does not specify either the start or the end of the navigation season. This season is jointly determined by the St. Lawrence Seaway Management Corporation in Canada and by the St. Lawrence Seaway Development Corporation in the United States. The regulation of outflows in accordance with the Boundary Waters Treaty and the IJC’s Orders of Approval, however, does take into account navigation.
5.4 Hydropower [top of page]
For hydropower, more electricity can usually be generated when there is a greater volume of water passing the stations. However, the consequent lowering of upstream levels decreases the head on the hydropower stations, thereby decreasing the amount of electricity generated for a given volume of water. Finally, extremely high outflows may exceed the capacity of the hydroelectric facilities, resulting in water being diverted around the generating equipment and being lost in terms of power generation.
The generating capacity of the Moses Saunders dam is around 10,000 m3/s when all units are available under typical conditions. Since the average outflow is 7,000 m3/s, the water is not spilt when outflow is increased, especially during dry conditions when the outflows are increased to augment low levels downstream. The water passes through the generators. The spillway at Long Sault dam was last used in 1998.
5.5 Environment [top of page]
The 1956 Order did not include consideration of the environment. Thus, the Board has had no direct authority to consider it in its deliberations. In 2009, The IJC asked the Board to consider the environment within the context of the existing Order. The Board has determined that there is little it can do to benefit the environment on Lake Ontario through its deviation authority but that there might be some limited benefits that could be achieved in specific instances in the St. Lawrence River.
Yes, the Lake Ontario-St. Lawrence River study concluded that regulation has had a negative impact on the wetlands and wetland-supported habitats of the Lake Ontario-St. Lawrence River Basin. While each wetland is unique, narrowing the range of water level fluctuations generally results in less wetland acreage and less diversity within the wetland plant communities. The Commission's Levels Reference Study Board concluded in 1993 that the reduction in the range of water level fluctuations resulting from regulation has adversely affected the extent and diversity of Lake Ontario's wetlands. It also concluded that altering natural water level conditions on Lake Ontario resulted in the appearance of undesirable plant species in its wetland habitats and has limited the capability of wetlands to support the overwintering water-dependent fish and wildlife populations. Further, there is also concern regarding the environmental impact of outflow regulation on wetland and fishery habitats in downstream areas of the river. More definitive data regarding all these impacts has been provided by studies conducted by the Lake Ontario-St. Lawrence River Study for the IJC from 2000 to 2006.
The construction of the dam at Massena and Cornwall created Lake St. Lawrence immediately upstream, thus changing the nature of that environment from a river to a lake environment. That change has brought about physical, chemical, and biological modifications. There are also concerns regarding impacts from the use of the shipping channel.
Regulation has reduced the number and, perhaps more critically, the timing and duration of extreme high and low levels on the river downstream. This may have impacted both wetland and fishery habitats. More definitive data regarding all these impacts has been provided by studies conducted by the Lake Ontario-St. Lawrence River Study for the IJC from 2000 to 2006.
5.6 Riparian and Shoreline Property Owners [top of page]
The major factors affecting long-term erosion rates include shoreline materials and structure, long-term patterns of sediment transport along the shore, and water levels. These factors have caused erosion since the last ice age and will continue to cause erosion in the future.
Strong winds are responsible for significant erosion over short time periods. When water levels are high, wind-driven waves can trigger significant short-term erosion events that would otherwise occur later or more gradually. They may also direct wave energy against existing erosion protection structures, sometimes resulting in damage. With extremely high water levels, waves may also directly impact on and damage dwellings and other structures near the shoreline. High water levels also result in localized flooding of roads and other public facilities and may result in damage to private property as well as public water and sewage facilities. The Lake Ontario-St. Lawrence River study found that damages to shoreline property and shoreline protection structures increases with increasing mean water levels on Lake Ontario. While long-term recession rates appear to be independent of water level fluctuations for some Great Lakes shoreline areas, water level fluctuations do play a role in determining long-term recession in others. The water level fluctuations may also influence beneficial shoreline sand redeposition and sand dune replenishment. More definitive data regarding all these impacts has been provided by studies conducted by the Lake Ontario-St. Lawrence River Study for the IJC from 2000 to 2006.
Timely management of the Lake Ontario outflows has consistently prevented extremely high water levels and flooding in the Montreal region. Regulation of Lake Ontario outflows has also greatly reduced the incidence of ice jams in the river, both upstream and downstream of the Cornwall/Massena area, thus reducing the flooding and shoreline damage often associated with these events. Finally, the construction of the St. Lawrence Seaway and power project created conditions enabling the establishment and growth of recreational boating on many areas of the St. Lawrence River. This occurred through the elimination of rapids, the creation of Lake St. Lawrence immediately above the dam, and the stabilization of river flows and water levels.
While shoreline protection may be effective in some instances, the best way to address flooding and erosion problems is through effective shoreline management. This is primarily a local, state, or provincial government function. The New York State Department of Environmental Conservation regulations pursuant to the N.Y. State Coastal Erosion Hazard Act implement several actions to reduce flooding and erosion losses along the Lake Ontario shoreline. The Provinces of Ontario and Quebec address flooding and erosion problems with flood plain management measures that provide easements and restricted building zones along the shore.
Actions by the NYSDEC and the Provinces of Ontario and Quebec that have been found to be effective include:
For new structures, flood and erosion setbacks that consider the long-term recession rates;
Prohibitions on removing or damaging natural shoreline protective features such as bluffs and dunes;
Prohibitions of any construction or structures within flood hazard areas;
Relocation of structures at risk;
Real estate disclosure requirements;
Acquisition of high-risk undeveloped land;
Limiting construction in flood plains; and
Purchase of flood easements within flood plains.
As a landowner, it is important to build with the knowledge that water levels fluctuate, and to know the extremes possible at your location. The Board urges everyone to be prepared to live within the full range of levels that have occurred. The Board strives to maintain the range of monthly mean levels of Lake Ontario below the upper limit of 75.37 m (247.3 ft) and above the lower limit (from April to December) of 74.15 m (243.3 ft) specified in the Orders of Approval. Know the extent to where high water and winds act and build accordingly. Structures, such as breakwaters and heavy stone may protect against strong wind action if built correctly. Residences should be built with sufficient setback to avoid flood and erosion damages into the future. The Board announces weekly levels and flows on the telephone and via e-mail; you may sign up to receive the e-mail bulletins or call the 1-800 number. The Board’s website also has guidelines on its publication page.
5.7 Recreational Boating [top of page]
Recreational boaters have problems navigating at different points on the lake and on the river, even when levels and flows are within the ranges in the Order. For example, a private dock or a marina built during high water levels may not be fully usable when water levels fall. Therefore, one action to alleviate this is to site, design, and maintain new and existing recreational boating facilities - taking into account the full range of water levels and flows, at minimum as defined in the Orders of Approval for Lake Ontario and as have occurred along the St. Lawrence River. This may necessitate the use of longer launch ramps, floating (rather than fixed) docking systems, and the financial commitment and permits to perform periodic maintenance dredging as needed to accommodate the planned use. Also, it must be recognized that some areas are shallow and cannot accommodate dockage for large recreational vessels. In addition, boaters should pay particular attention to navigation charts during low water periods, even in waters with which they may be familiar.