Lake Simcoe watersheds Courtesy of Lake Simcoe Conservation Authority


1981 - 1985


LSEMS - Implementation Program (1985 -    )

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Background Information

Adapted from: Environment Information Bulletin, Spring, 1990.


The purpose of the five-year Lake Simcoe Environmental Management Strategy is to restore the water quality of Lake Simcoe so that it will support a naturally reproducing cold-water fishery.


The strategy's partners are:

  1. Ministry of the Environment,
  2. Ministry of Natural Resources,
  3. Ministry of Agriculture and Food and
  4. Lake Simcoe Region Conservation Authority.

The conservation authority will co-ordinate the activities of the participants and the concerns of its member municipalities. (A conservation authority is supported by the Ontario government and the municipalities within its area of responsibility.)


The Ministry of the Environment will play a major role in regulating phosphorus discharges into Lake Simcoe, monitoring and researching ways to improve water quality.

The major sources of phosphorus in waterways are run-off from fertilized fields fertilizers contain phosphorus and discharges from municipal sewage treatment plants. Many household soaps, detergents and cleaning compounds contain phosphorus.


The Ministry of the Environment is committed to holding the line on the amount of phosphorus discharged into Like Simcoe. To do this, the ministry will closely monitor municipal sewage treatment plants.

To date, ministry-imposed control, at the Barrie And Orillia plants, and the diversion of sewage from Newmarket and Aurora to the Duffin Creek sewage treatment plant east of Toronto, have cut phosphorus discharges from sewage treatment plants into the lake by more than 50 per cent.

In recent years, total phosphorus concentrations in Cooks Bay near Keswick have been more than 25 parts per billion (ppb) and in Kempenfelt Bay near Barrie have been more than 20 ppb. To avoid algae blooms, phosphorus concentrations should not exceed 20 ppb.

To hold this line, the ministry has told area municipalities that they must not increase their phosphorus discharges into Lake Simcoe. This means that municipalities must upgrade their sewage treatment plants to keep pace with residential, commercial and industrial growth.


Phosphorus is one of the nutrients that plants, such as algae and weeds, need to grow. When a lake has a high level of phosphorus, algae and weeds proliferate. When they die, they sink to the bottom of the lake and decay. In the process, the decaying plants consume the oxygen that fish, such as lake trout that prefer the cooler water often found in the deeper reaches of a lake need to survive.

Ministry scientists are developing a computer-based model, which will help them predict how phosphorus, oxygen and plants will interact and the effect this will have on fish habitats. Ministry scientists will also use the model as a guide to regulate phosphorus discharges.

A similar approach was used with success by Canadian and American jurisdictions to reduce high phosphorus levels in Lake Erie.


Ministry scientists will also monitor the lake's health by examining other indicators such as phytoplankton a small, suspended species of algae. The ministry will monitor the amount of phytoplankton present in four water intakes in the Lake Simcoe watershed area, Brechin, Beaverton, Keswick and Sutton.

Ministry scientists will also regularly test water quality at 10 stations in the open lake.

Furthermore, as most of the agricultural phosphorus flowing into Lake Simcoe comes from the heavily cultivated Holland River watershed, the ministry will monitor water quality at key points on the river's tributaries. Checking water quality in this area has revealed that the amount of phosphorus flowing out of the Holland Marsh dropped to 3.5 tonnes in 1987 from 11.5 tonnes in 1982.

Finally, the ministry will monitor water quality in other rivers in the Lake Simcoe basin.


Until the mid-1970s, Lake Simcoe and the rivers and streams which drain into it, were considered by anglers to offer some of the best fishing in the province. But as the lake's water quality deteriorated, algae blooms became common, whitefish practically disappeared from the lake, and lake trout stopped reproducing.

In addition, Orillia was having problems with the taste and odor of its drinking water.

Tourists, resort operators and municipal employees complained to provincial ministries and the Lake Simcoe Regional Conservation Authority about Lake Simcoe's water quality. Government scientists said that high phosphorus levels caused the problems.

In response to the complaints, the Lake Simcoe Environmental Management Strategy was launched.

Between 1980 and 1985, the ministries of Natural Resources, Agriculture and Food and the conservation authority worked together to find the sources of phosphorus and the effects on the lake's health.

At the same time, Environment Ontario acted to reduce the amount of phosphorus discharged into the lake. Barrie and Orillia, for example, were required to upgrade their sewage treatment plants. Between 1981 and 1988, the two cities reduced the amount of phosphorus, which they discharged into the lake, by one-third to about eight metric tonnes a year. Also, sewage from Newmarket and Aurora was diverted to the Duffin Creek sewage treatment plant on Lake Ontario via the York-Durham trunk sewer a large sewer running through the regional municipalities of York and Durham. This reduced the amount of phosphorus entering the lake by six metric tonnes a year.

The four ministries and the conservation authority produced a report calling for a co-ordinated five-year program to protect and improve the water quality of Lake Simcoe. This is the Lake Simcoe Environmental Management Strategy.

Additional Background Information adapted from the Summary of: 

Lake Simcoe Environmental Management Strategy:
Final Report and Recommendations of the Steering Committee. 1985.

The Lake Simcoe-Couchiching Basin Environmental Strategy study as well as earlier research and monitoring work have indicated that Lake Simcoe has been receiving an excessive supply of phosphorus, causing over-abundant growths of algae. This disrupts the Lake's ecosystem, results in critically low dissolved oxygen levels in the deeper Lake waters and is causing a decline in the populations of desirable cold-water fish species. In response to ongoing concerns with the Lake water quality and recommendations for further research, the Cabinet Committee for Resources Development initiated the Lake Simcoe Environmental Management Strategy (LSEMS) studies, designating the Ontario Ministry of the Environment as lead agency (CCRD, 1979).

The 1979 Cabinet Committee directive initiating LSEMS identified three phosphorus control measures to be undertaken with the objective of reducing annual phosphorus inputs to the Lake to 87 metric tonnes from a projected 1983 loading of 105 metric tonnes. These were:

  1. the diversion of sewage to the Duffin Creek Water Pollution Control Plant on Lake Ontario from Newmarket and Aurora via the York-Durham trunk sewer to achieve a 6 tonne phosphorus reduction;
  2. upgrading of sewage treatment at Barrie and Orillia to reduce phosphorus loadings by 8 tonnes, and
  3. the reduction of phosphorus loadings originating from agricultural activities by 4 tonnes.

The major components of LSEMS were the Phosphorus Sources, Loads and Remedial Measures Studies and the Lake Simcoe Water Quality and Fisheries Studies. The overall objectives of these studies were:

  • the determination of phosphorus inputs to Lake Simcoe;
  • the identification and evaluation of measures designed to reduce annual phosphorus inputs to the Lake from agricultural sources by four tonnes per year;
  • the establishment of base line physical, chemical and biological data to facilitate:
    future evaluation of Lake Simcoe water quality,
    determination of long range water quality trends, and
    measurement of the effectiveness of adopted remedial measures.

Intensive water quality monitoring stations were established throughout the open Lake, on downstream reaches of major tributaries and at a number of locations on the Holland River System. Research efforts dealt with:

  • soil erosion
  • streambank erosion and livestock problems
  • phosphorus loadings from the Holland River vegetable polders
  • phosphorus in the lower Holland River
  • algae and aquatic plant growth in the Lake
  • stormwater runoff from built-up areas and
  • phosphorus in sewage effluent.

The data collected from the tributary monitoring stations indicated a clear pattern of high instream phosphorus concentrations in the southwest portion of the basin, diminishing to the north and east. Exceedences of the Ministry of the Environment guidelines for instream phosphorus concentrations were encountered throughout the basin.

The highest lake water concentrations of phosphorus were consistently found in the southern areas of Cook Bay. Concentrations declined in the Bay towards the main body of the Lake. A similar pattern is found in Kempenfelt Bay with elevated concentrations being found at the head of the Bay and decreasing eastward towards the Lake. The
total phosphorus concentrations in the main body of the Lake are consistently lower than those measured elsewhere in the Lake. The types of planktonic algae found in the Lake were typical of those found in nutrient enriched lakes.

Total annual phosphorus loadings to the Lake from sources discharging into the Lake and from the tributaries ranged from 68 to 103 tonnes between 1982 and 1984, and averaged 82 tonnes. On average, tributary loads, originating from various land uses within the sub-basins, were 64% of the total Lake loading:

Year-to-year loadings exhibit a substantial variation as a result of variations in factors such as total precipitation. Both the 105 tonne projection for 1983 and the 87 tonne target cited above would appear to be within the general range of observed loadings. This implies that a single target loading figure (such as the 87 tonne value) is of limited practical value in establishing implementation strategies. It is more important to set interim phosphorus loading reduction objectives until the oxygen/phosphorus relationship in the Lake is better understood.

Estimated mean annual phosphorus loadings delivered into tributary streams amounted to 139 tonnes during the study period. Only 37% of these inputs were estimated to enter the Lake, reflecting the impact of instream processes such as settling of suspended sediments that remove phosphorus from stream flows.

Estimated loadings to streams from individual sources varied from a high of between 80 and 120 tonnes associated with soil erosion to only 2.9 tonnes associated with streambank erosion. Inputs from built-up areas to streams were estimated to range from 7 to 10 tonnes while loadings from built-up areas directly into the Lake were estimated to range from 13 to 16 tonnes.

The phosphorus control measures proposed by Cabinet Committee have been or are being implemented. The diversion of sewage from Aurora and Newmarket was brought on line in 1984. Upgrading and modification for advanced phosphorus removal are complete at the Orillia water pollution control plant while work is under way at the Barrie plant.

Modelling analysis suggested that a 2 to 3.5 tonne reduction of phosphorus entering the Lake could be achieved by implementing conservation practices on erosion-prone cropland. Harvesting of duckweed from the Holland Marsh polder canals could result in a 0.5 to 1.0 tonne reduction of phosphorus inputs to the lower Holland River. Practical measures are also available to control phosphorus inputs from streambank erosion and from livestock operations. A 4 tonne loading reduction from agriculture is, therefore, quite feasible. A long time frame of perhaps a decade or more should be
anticipated for the implementation of these measures since they involve a great number of private sector participants and extensive promotional work by government agencies.

The investigative efforts and discussions engendered by the LSEMS project have culminated in a series of recommendations that touch on topics ranging from specific remedial action through to broader questions of policy and research.

Pre-LSEMS Reports (8)
  1. Lake Simcoe and its Environs. 1 July, 1893. A.F. Hunter. Interesting overview of the Lake Simcoe Region in late 1800s.  47p.
  2. Biological Survey of the Holland River, 1965. Aug. 1966. M.G. Johnson and G.E. Owen.
  3. A Preliminary Report on Water Quality Characteristics of Kempenfelt Bay and Adjacent Lake Simcoe. 1970.  D.M. Veal, A.R. Clark. [483 KB]
  4. Aquatic Weed Growths in Lake Simcoe. 1971. E.S. Millard, D.M. Veal. [641 KB]
  5. Lake Simcoe: A Water Quality and Use Study.  June 1975. [3357 KB]
  6. Mercury in the Lake Simcoe Aquatic Environment. Sept., 1978.  [1113 KB]
  7. Lake Simcoe-Couchiching Basin Environmental Strategy. 1979. [832 KB]
  8. Cookstown - Innisfil Creeks Water Quality Survey, Jan. 1980. A.V. Choo-Ying, [658 KB]
  9. Water Quality Characteristics of Lake Simcoe, 1980. March, 1982. J.E. Dobson, K.H. Nicholls, M.B. Jackson. [1767 KB]

Lake Simcoe Environmental Management Strategy Report List (9)
n/a Lake Simcoe Environmental Management Strategy: Final Report and Recommendations of the Steering Committee. 1985. [1977 KB]
A.    Land Sub-Group. 1985. Overview of Phosphorus Sources, Loads and Remedial Measures Studies.
A.1 Lake Simcoe Tributary Water Quantity and Quality Data Report. - Frank, D., D. Henry, J. Antoszek and F.Engler. 1985.
A.2 Newmarket Urban Test Catchment Data Report. - Frank, D., D. Henry, T. Chang and B. Yip. 1985.
A.3 Streambank Erosion Inventory. Volume I. - Antoszek, J., T. Stam and D. Pritchard. 1985.  [2103 KB]
A.3 Streambank Erosion Inventory. Volume II. - Antoszek, J., S. Meek, K. Butler and O. Kashef. 1985. [3770 KB]
A.4 Calibration Summary of Holland Marsh Polder Drainage Pumps. - Rupke and Associates. 1985. [1535 KB]
A.5 Phosphorus Control by Duckweed Harvest -Holland Marsh Polder Drainage System. - Limnos Limited. 1985.
A.6 Phosphorus Modelling and Control Options: Technical Report A.6.  1985. D. Draper, et al. [5555 KB]
B.    Overview of Lake Simcoe Water Quality and Fisheries Studies. - Lake Sub-Group. 1985.
B.1 Water Quality Characteristics of Lake Simcoe - 1980-1984. - Humber, J.E. 1985.
B.2 Dichotomosiphon tuberosus, a benthic algal species widespread in Lake Simcoe. 1985.  Neil, J.H.& G.W. Robinson. [739 KB]
Summer Nutrient Conditions in the Lower Holland River prior to Diversion of Municipal Inputs. - Angelow, R. and C. Robinson. 1985. [1911 KB]
B.4 Aquatic Plant Assessment in Cook Bay, Lake Simcoe. - Neil, J.H., G.A. Kormaitas and G.W. Robinson. 1985. [1114 KB]
n/a Community Relations Report, 1985.  Sept. 1986.  H.D. Gault   [272 KB]

Post-LSEMS Reports (1)
  1.  Growth of Macrophytes in Cook's Bay, Lake Simcoe. March, 1988. J.H. Neil, J. Graham, J. Warren [730 KB]]


Related Links



LSEMS Implementation Program (1985 -    )
O.M.E. Report List Sorted by Conservation Authority / Watershed Region 


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Last Revised: Friday, February 15, 2019 12:58:26 PM