Update: 23 August, 2010

Background

Most of us are aware that the levels on our lake are controlled to some extent, but we wonder why flooding occasionally occurs, and sometimes levels drop late in the summer. There is a dam at Carleton Place, so why can't the lake be maintained at a constant level?

There is no simple answer because the problem is quite complex. This lake is part of the Mississippi River watershed, a vast network of lakes, rivers and streams with a drainage area of 3750 sq. km. The river is 212 km long and there are approximately 268 lakes. Most of the water that feeds this system arrives during a short period of time during the spring runoff; average rainfall in the area is not sufficient to provide flows to maintain suitable lake levels, especially on Dalhousie and Mississippi Lakes. In order to manage these two conflicting situations, (and many other issues including ecological, wildlife habitat, erosion, etc.) the various dams on the watershed are operated to minimize flooding while maintaining a supply of water in the western reservoir lakes to augment the lower flows in late summer. There are many other conflicting water management issues which must be addressed.

Mississippi Valley Conservation has the task of managing the water levels on this watershed. Although an informal operating plan has been 'tweaked' over the years, a formal Mississippi River Water Management Plan is presently being developed.

The following discussion of general operating principals was provided by Gord Mountenay, Water Management Supervisor, Mississippi Valley Conservation.

 Mississippi River Watershed General Operating Principals

All of the dams in the western portion of the Mississippi River watershed were originally built to maintain enough water in the system to allow timbers to be floated downstream three or four times a year. The purposes of these structures have become diversified with the changing conditions in the watershed. As well as flood protection, low flow augmentation, ice management, erosion control and recreation, they also must be operated to maintain specific flow and level requirements for lake trout, walleye, bass, pike and as much as possible all other fish species. Stable levels are required for wildlife such as loons, frogs, muskrat and beaver. Continuous flows must be maintained to sustain the ecological integrity of the system including flushing rates for maintaining water quality in the lakes and rivers. If possible, flows are maintained to allow hydro producers to continue operating their generating facilities. The management of the river system has become increasingly more difficult as storms and droughts have tended to be more severe and more restrictions have been placed on how dams may be operated. This watershed historically receives approximately 750 mm of precipitation annually; it loses approximately 300 mm of that to evaporation annually, thereby leaving only 400 mm for groundwater supply, to fill the upper lakes and to maintain a minimal flow throughout the year.

There are six major lakes in the watershed which act as storage reservoirs in the spring to alleviate flooding downstream of Crotch Lake. These are Shabomeka, Mazinaw, Kashwakamak, Big Gull, Mississagagon and Crotch Lakes, all of which have water control structures at their outlets. There are two other notable lakes on the main branch of the Mississippi River, being Dalhousie and Mississippi Lakes. Neither of these lakes have a dam at their outlet although Mississippi Lake is influenced by the Carleton Place Dam under low flow conditions and limited influence under high flow conditions due to configuration of the channel leading to the dam from the lake. Both of these lakes are heavily developed.

Every fall, the dams are operated to draw down the lakes to provide storage for the spring runoff. As snowmelt and spring rains occur, the lakes are gradually filled to reach the summer target levels for recreation and tourism. Conditions must be monitored to ensure that the targets can be reached while ensuring that adequate storage remains for late spring rainfalls and sufficient flows and levels are maintained for spawning fish. In doing so, there is a reduction in flooding to areas downstream as the uncontrolled flows from Antoine and Cranberry Creeks, the Fall and Clyde River systems move through the central and eastern portion of the watershed. Once the runoff is over, all of the control dams, except for the Crotch Lake Dam, are operated to maintain relatively stable elevations on the lakes for recreation throughout the summer months. Crotch Lake Dam is unique as Crotch is the only true reservoir lake on the system.

From late June through early October, Crotch Lake is drawn down to ensure flows in the lower portion of the river. Under normal conditions, approximately 60% of the flow in the river comes from Crotch Lake. During the droughts of 2001 and 2002, 100 % of the flow in the river below Crotch Lake came from Crotch Lake as all other tributaries dried up to virtually nothing. The upper lakes were operated to bring levels down to the bottom of their respective target ranges to maintain flow in the river in the western portion of the watershed and areas downstream. Crotch Lake normally fluctuates from 2.5 to 3.5 m (depending on amount of precipitation) over the course of the summer, every summer. Throughout the fall, as the other lakes are being drawn down, Crotch Lake is filled again while still maintaining at least a minimum flow to ensure the ecological integrity of the system downstream of the dam. From January through March the lake is again drawn down to perform the same low flow augmentation function over the remainder of the winter months and to maximize storage in the lake for the spring.

So there is some of the background and rationale for the present operating plan. The following article describes the effort to produce a formal operating plan, providing a brief background and purpose, schedules, and website address where additional information is available.

While the Mississippi River Water Management Plan (MRWMP) was undertaken because hydro facilities exist on the Mississippi, hydro production is not the driver for water management operations on the Mississippi. This is highlighted in the article title, that the title, that the MRWMP is "an integrated approach" to maximize all uses of the river including waterpower, flood control, low flow augmentation, fish and wildlife, tourism and recreation.

Canadian Hydro Developers Inc., Enerdu Power Systems Ltd., Mississippi River Power Corporation, Ontario Power Generation and the Mississippi Valley Conservation undertook a study to review the operational management of water control structures (dams and hydro-power facilities) on the Mississippi River system. The purpose of this project was to develop a water management plan that considers the interests and concerns of all users through balanced operational management of water levels and flows for the potentially competing uses of the Mississippi River waters. The generating facilities and water control structures subject to the plan are: Galetta Generating Station (G.S.), Almonte G.S., Enerdu G.S., Appleton G.S., Carleton Place Dam, High Falls G.S., Crotch Lake Dam, Mississagagon Lake Dam, Big Gull Lake Dam, Kashwakamak Lake Dam, Mazinaw Lake Dam and Shabomeka Lake Dam.

The Mississippi River Water Management Plan final report was released June 15 2005.

For more information about the Mississippi River Water Management Plan, please contact:

Gord Mountenay, Water Management Supervisor
Mississippi Valley Conservation
Lanark
Phone: (613) 259-2421, extension 233

Email: Gord Mountenay

Sarah MacHardy
Ontario Ministry of Natural Resources
Phone: (613) 258-8386

Email: Sarah MacHardy

Or visit the website
http://www.mississippiwaterpowerplan.com

MLA Particiption

As part of the planning process, a Public Advisory Committee (PAC) was established to provide advice and comments to the facility owners and MNR on the development of the water management plan and to assist in carrying out the public consultation program. The volunteer members of the PAC have varied backgrounds and interests, including: landowners with property on or near the river, municipalities, local business, tourism & other industries, anglers & hunters, lake associations, naturalist clubs, recreational groups and other resource user groups. Ed Carew, an MLA Director, was one of the 12 Public Advisory Committee members for the Mississippi River Water Management Plan for Waterpower project, and has continued as a member of the Standing Advisory Committee (SAC).