top of page

Home > Environment > Water


Water is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere, and the fluids of most living organisms. It is vital for all known forms of life, even though it provides no calories or organic nutrients. (Wikipedia)

One of MLA's core tasks is to make everyone around the lake aware of this vitality, hence the elaborate coverage below:

Water Level Chart

Water Level Chart


The  Mississippi Lake water level chart is produced by the MLA, using information gathered by the Mississippi Valley Conservation Authority (MVCA).  Here are direct links to the MVCA website for additional information regarding the entire Mississippi River Watershed:

Flood Warning information. 

It is important to note that severe storms, with subsequent heavy rainfall, may result in fairly rapid increases in water levels.  Consult the MVCA for detailed information and guidance regarding flooding conditions.

Water Levels elsewhere in the Watershed. MVCA tracks lake levels and stream flow throughout the watershed.


Mailing Lists to subscribe directly to MVCA for information regarding a variety of topics.

Water Quality Sampling

Water quality has been consistently ranked as the top priority by respondents to MLA several surveys and studies.  As a result, Water Quality initiatives figure prominently in the list of Action Items included in the MLA Lake Plan, launched in 2015. 

  • History - Water quality information on Mississippi Lake has been gathered under a variety of programs since 1968, primarily to examine the trophic status of the lake (the amount of biomass present in the lake). 

    • Please consult this table which indicates how the measurement of total phosphorus concentration, water clarity, and chlorophyll A levels can be used to assess the overall trophic status of the lake.  Mississippi Lake, being shallow and having a broad surface area, is subject to excessive aquatic vegetation and algae growth and was considered to be eutrophic in the late 1960’s through much of the 1970’s.

    • Water sampling includes measurement of:

      •  total phosphorus, since elevated phosphorus concentrations are a major factor in promoting plant growth and algae blooms;

      • water clarity, which is primarily affected by the amount of suspended algae, using a Secchi Disc; and

      • the concentration of active chlorophyll (chlorophyll A), as a measure of the amount of photosynthesizing plants (algae and phytoplankton) in the water.

    • Sampling programs have also included other water quality parameters such as dissolved oxygen, pH and temperature, although these are not addressed in detail in the annual State of the Lake reports.   However, it is reassuring to note that dissolved oxygen measurements have and continue to show life-supporting oxygen concentrations throughout the water profile.

  • Water Rangers ( was established in 2016 by a group of dedicated web developers and passionate conservationists to map water quality conditions and issues throughout eastern Ontario.  Occurrences such as blue-green algae appear on the map, along with photographs and atmospheric conditions.  The mapping is coordinated with Citizen Water Watch, a mobile reporting system.  The Water Rangers platform invites visitors to Add an Observation, Report an Issue or View the summary for any selected body of water.  In the case of Mississippi Lake, we can see previously reported incidents mapped in the location where they occurred, along with the relevant reporting details.

    • Be a Water Ranger and report your observations.

    • This is a great site to visit if you want to see all the water quality information that has been compiled for locations on  Mississippi Lake.  Each location has a list of all the observations that have been logged, along with trends in the various parameters.  Simply go to the  Mississippi Lake Map and browse to your heart's content!


    Each year, the MLA publishes a State of the Lake Report to keep our membership aware of current water quality, and historic trends.


Water Quality Sampling
Watershed Management Plan

Mississippi River Watershed Management Plan


  • Provide updated information

  • Lot of links don’t work

Most of us are aware that water 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, which can lead to much increased water levels and flooding.  However, for most of the year, the average rainfall in the area is not sufficient to provide flows to maintain suitable lake levels, especially on Dalhousie and Mississippi Lakes.  Various dams on the watershed are operated by MVCA to manage these two conflicting situations, (and many other issues including ecological, wildlife habitat, erosion, etc.). 


Mississippi River Water Management Plan (MRWMP)

The Mississippi Valley Conservation Authority has the task of managing the water levels in this watershed.  Although an informal operating plan had been used over the years, a formal Mississippi River Water Management Plan was developed and approved for use in June, 2006.


The Final Report of this plan is an extensive study of the numerous factors affecting water management in this system, and is an essential reference source for understanding the issue. Ed Carew, a former MLA Director and Vice President, was one of the 12 Public Advisory Committee members for the Mississippi River Water Management Plan for the Water Power project, and has served as Chair of the Standing Advisory Committee (SAC).


While the MRWMP was undertaken because hydro facilities exist on the Mississippi, hydro production is not the driver for water management operations.  During the preparation of the Mississippi River Water Management Plan much consideration was given to an integrated approach to maximize all uses of the river including water power, flood control, low flow augmentation, fish and wildlife, tourism and recreation.


Carleton Place Dam Operation

This is of particular interest to residents of Lake Mississippi and the communities immediately downstream.  The operating range for the Carleton Place Dam is between 133.93 m and 134.50 m. Within this range, the dam is operated to achieve a summer target level on Mississippi Lake of 134.35 m by the long weekend in May and to maintain a target range of 10 cm above and below the optimum level for Mississippi Lake, from the end of May to the start of the following freshet (spring runoff).

Due to constrictions in the natural channel at Bridge Street in Carleton Place, which has less conveyance capacity than the Carleton Place Dam, water levels on Mississippi Lake cease to be influenced by the operation of the dam once 25 stop logs have been removed and/or stream flows have exceeded 150 cm. This will result in water levels on Mississippi Lake normally ranging from 134.9 m in the spring to 133.95 m in the fall.  Stream flows in excess of 150 cms will result in higher water levels on Mississippi Lake.

MVCA provides a detailed explanation of the general operating principles for dams on the Mississippi River.


Floodplain Considerations

Mississippi Lake is a relatively shallow lake with a substantial portion of low lying shoreline. During periods of heavy precipitation or during the Spring freshet, the shoreline is vulnerable to flooding. Important components of watershed management are the identification of these vulnerabilities and the development of regulations to minimize risk and damage to life and property. Accordingly, the MVCA has undertaken an extensive floodplain mapping project, and provides excellent information on their website regarding flood prone areas, flood warning messages, and regulations for building on a floodplain.

Ice Out Dates
Ice Out Dates

The following are the current and past ice-out dates observed from Ebbs Bay Shore on the Big Lake, as well as from observers in other parts of the Mississippi Lakes system. If anyone can provide information for earlier dates, that would be much appreciated.  Also, some of you may have observed different dates, since many bays trap ice for a few days after it leaves the Big Lake.


Over the last 30 years:  

The  earliest ice out date was 21 March 2024

The latest ice out date was 27 April 2018

The average ice out date has been 15 April

Ice Out Dates:

1994 - 24 April

1995 -   4 April

1996 - 23 April

1997 - 26 April

1998 -  10 April

1999 -   11 April

2000 -  2 April

2001 -  18 April

2002 - 12 April

2003 - 21 April

2004 - 19 April

2005 - 19 April

2006 - 13 April

2007 - 21 April

2008 - 21 April

2009 -  5 April

2010 -   4 April

2011 -   13 April

2012 -  25 March

2013 -  19 April

2014 -  26 April

2015 -  21 April

2016 -  16 April

2017 -  17 April

2018 -  27 April

2019 -  24 April

2020 - 10 April

2021 -   4 April

2022 - 15 April

2023 - 16 April

2024 - 21 March

2025 -

2026 -

2027 -

2028 -

2029 -

2030 -

Ice Out Dates

  • Blue-green algae are microscopic, plant-like organisms that occur naturally in ponds, rivers, lakes and streams. Although often blue-green, they can also be olive-green or red. 

  • They are not normally visible in the water, but populations can rapidly increase to form a large mass or scum called a bloom when conditions are favourable.

  • Blooms most commonly occur in late summer and early fall.

  • Dense blue-green algae blooms may make the water look bluish-green, or like green pea soup or turquoise paint.

  • Fresh blooms often smell like newly mown grass, while older blooms may smell like rotting garbage.

Here are two very informative articles on blue-green algae (BGA):

The Algae of Kawartha Lakes - an excellent report commissioned by the Kawartha Lake Stewards Association in 2012, that provides great information on the types of algae that grow in Eastern Ontario lakes, when they become a hazard, and what controls their growth.  This information is equally relevant to Mississippi Lake. 




Blue-Green Algae    

By:  Kelly Stiles
Aquatic Habitat Biologist
Mississippi Valley Conservation Authority

Bluegreen algae.png

Blue-Green Algae

Blue Green Algae
bottom of page