Summary and
from the

 Thames River Basin
Management Study


Report Summary


Thames River Implementation Committee (TRIC)


The two main water management problems in the Thames River basin are water quality impairment and flooding. Impairment of surface water quality is primarily caused by excessive inputs of nutrients, oxygen consuming materials, bacteria and suspended solids. Major urban sources of these contaminants include sewage treatment plant effluent, storm and combined sewer discharges and runoff from urban areas. Municipal drains, field tile systems, surface runoff from fertilized fields, drainage from intensive feedlots, treated effluent from rural industries, and the free access of cattle to streams are major rural sources of water quality impairment. Excessive aquatic plant growth and unpleasant aesthetic conditions are the most visible signs of water quality impairment; however, the less visible problems of low dissolved oxygen levels and high bacteria levels are also significant. This impairment has led to the curtailment or restriction of legitimate water uses in the watershed. Most severely affected by this impairment are fish and aquatic life and recreational water uses.

Recurrent flooding is the other most significant problem in the watershed, particularly in St. Marys, Woodstock, London, and the area from Thamesville through Chatham to Lake St. Clair. Average annual flood damages in the watershed were calculated to be over 1.5 million 1975 dollars, of which 57 percent is in Chatham and 20 percent in the vicinity of London. Related in part to flooding is erosion of streambanks and dikes, primarily in the lower watershed. Erosion of topsoil is also a significant problem.

The inadequacy of water-based recreational facilities to meet demands and the potential loss of prime agricultural land were also identified as problems common to the watershed. Other water management problems of local importance include negative effects of artificial land drainage, water supply interference and ground water quality impairment. Communication and co-ordination problems were also noted.

In order to develop effective courses of action to resolve these problems, water management objectives were developed and alternative courses of action were evaluated. With respect to water quality objectives, it was concluded that the short term objective should be to maintain existing water quality where it is satisfactory for fish and aquatic life and recreation, and to improve quality to this level where it is presently degraded. The long term objective is to upgrade water quality as much as possible in order to enhance conditions for fish and aquatic life, as well as to maximize other beneficial water uses. Dissolved oxygen criteria and other specific water quality criteria which would allow this objective to be met were developed.

It was concluded that flood control in the basin would require the construction of one or more large dams, and a detailed flood control benefit-cost analysis of proposed major dams was carried out. Moreover, as flood control and water quality improvement options are closely interrelated, various combinations of the proposed reservoirs and waste management options were examined in a systems context.

As provincial studies of both the Lake Erie and Southwestern Ontario regions recognized London to be a major growth centre, and recommended it continue in that role, one objective was to develop a water management plan which would allow London to expand to its projected 2001 population while maintaining satisfactory stream water quality. This will also allow for the re-direction to London of population growth from other areas of the watershed where the capacity of resources to sustain growth will be reached within the planning horizon.

However, it is recognized that a variety of other considerations must be taken into account in determining the most desirable distribution of growth. Population projections based on official plans and 1961-71 trends, giving a 2001 population of 500,000 at London, were used in evaluating water management options. However, a significantly lower growth rate, such as a recent TEIGA estimate of a 2001 population at London of 338,000 to 350,000, would fundamentally alter the evaluation of options. Thus, options which would meet water quality objectives at lower projected populations were also considered. On this basis, the major waste management options available to. the City of London were reduced to: tertiary treatment (to stream quality effluent); diversion of sewage by pipeline to Lake Erie; or the operation of the Glengowan dam, primarily for flow augmentation, with the continued use of conventional sewage treatment.

The proposed reservoirs and the sewage treatment options for London were then evaluated in system configurations. The primary evaluation criteria for this analysis were flood control benefit-cost ratios and the total system net cost in present value terms. Twenty-two system options were evaluated in detail. The next analytical stage involved evaluation of non-quantifiable factors such as recreation and environmental effects of capital works. Additional objectives utilized at this stage were: to minimize both the loss of prime agricultural land and environmental disturbance due to capital construction projects, especially dams; and to increase water-based recreational facilities in the basin.

When all these factors had been considered, it was concluded that the preferred option is to construct the Thamesford dam primarily for flood control, the Glengowan dam primarily for flow augmentation, and to utilize conventional treatment at London. However, if it is decided that development of a limestone deposit precludes construction of the Thamesford dam, the preferred option is to construct the Wardsville dam for flood control, the Glengowan dam primarily for flow augmentation, and to utilize conventional treatment at London. If the growth limitation of 480,000 for London associated with this option is decided to be unacceptable, then other options, such as provision of tertiary treatment or construction of a sewage pipeline to Lake Erie can be considered.


No. Recommendation
1 As the Glengowan dam is common to each of the preferred options, construction of the Glengowan dam first would offer maximum flexibility in choosing other capital construction projects. Decisions as to whether to construct the Wardsville dam or the Thamesford dam could then be made. The decision as to whether to utilize conventional treatment or eventually a sewage pipeline from London to Lake Erie could be deferred to the early 1990's.

Accordingly, it is recommended that the Glengowan dam should be constructed first, for the primary purpose of flow augmentation. Furthermore, a study should be made of what type and level of recreational use, if any, could be provided at the reservoir.

2 It is further recommended that the Upper Thames River Conservation Authority and the Ministry of Natural Resources investigate in detail, as soon as possible, the question of the limestone deposit at the Thamesford dam site to determine the opportunity cost associated with its development, so that a decision can be made as to the feasibility of constructing the Thamesford dam.
3 If construction of the Thamesford dam is feasible, then the Thamesford dam should be built primarily for flood control purposes. Furthermore, a study should be made of the desirable level of recreational use of the reservoir, ensuring that such use would not seriously constrain the primary use of the reservoir.
4 If construction of the Thamesford dam is not feasible, then the Wardsville dam should be constructed for flood control purposes only. A flow retarding structure rather than a conventional dam should be constructed to minimize the loss of agricultural land and to protect the yellow pickerel runs and spawning grounds. Detailed studies should be undertaken to ensure the design will permit the safe passage offish, and to determine on a benefit-cost basis whether a 43,000 acre-foot or a larger retarding structure is the more economical. The environmental effects and the effects on road communications of the larger versus the smaller structure should be considered. There should also be close consultation with Indian bands concerning the effects on reservation lands.
5 Prior to construction of any major dam, detailed studies should be undertaken to examine environmental effects, to determine methods of minimizing such effects, and to determine what type of discharge structure and operating practices would best protect both reservoir and downstream water quality.
6 As noted above, implementation of any one of the preferred options allows deferral for several years of a decision by the City of London as to whether to continue discharging treated sewage to the Thames River or to utilize a sewage diversion pipeline to Lake Erie.

Accordingly, the City of London should immediately institute plans to upgrade its sewage treatment facilities to meet the waste loading guidelines outlined in this report. Specifically, this involves providing an effluent from all treatment plants equivalent in quality to the effluent from the Greenway sewage treatment plant as defined in this report.

7 Although the major options have great significance to basin wide water management, they by no means deal with all the basin's water resource problems. Local water management problems can have a cumulative effect, so that a localized type of problem, recurring at several different locations, can have basin wide implications. A wide range of management options to deal with urban, rural, reservoir-related and flooding problems has been considered and applied on a stream reach and municipality basis.

Urban oriented options include varying levels of treatment of sewage and industrial wastes, and growth restrictions. In areas where the remaining waste assimilative capacity of streams is limited, municipalities proposing additional growth can consider the installation of advanced tertiary waste treatment plants producing a highly polished effluent equivalent to stream water quality, or waste storage for summer spray irrigation or discharge during periods of adequate flow. However, for smaller municipalities, the costs of the required tertiary treatment may be prohibitive. Moreover, the costs of property acquisition for waste storage can make this uneconomical and this approach often involves the use of prime agricultural land. The alternative to the above treatment options is growth restrictions.

At several municipalities in the basin, the waste assimilative capacity of the receiving stream has been reached or exceeded. Accordingly, it is recommended that the municipalities of Mitchell, Stratford, Tavistock, Glencoe, Tilbury and Ridgetown should not increase their waste loadings from all sources to the receiving stream, and in some cases should reduce these loadings, as described in chapter 8 of this report.

8 Receiving streams at other municipalities in the basin have varying capacities to assimilate additional waste loadings. The additional assimilative capacity at the municipalities of Woodstock, Beachville, Ingersoll and Lambeth is limited and long term growth would be inadvisable from a water quality viewpoint. At the municipalities of Dorchester, St. Marys, Bothwell, Thamesville, and Chatham the additional waste assimilative capacity is not as limited.

Accordingly, these municipalities should adopt sewage treatment techniques selected from approved options as described in this report, either to provide immediately required upgrading or to accommodate additional growth if such growth is found to be desirable when other factors are considered.

9 Control of urban runoff is an important consideration in the basin. Although the significance of pollution loads from this source at each municipality was not documented during this study, urban runoff is recognized as a source of stream impairment.

Thus, all municipalities should immediately undertake studies to determine the significance of existing urban runoff and runoff associated with future development as a source of pollutants, and take steps to control this waste input where it is found to constitute a water quality problem.

10 Most industries in the basin lie within municipal boundaries and discharge wastes and non-polluted process waters to municipal sanitary and storm sewage systems respectively. Most municipalities have enacted sewer use bylaws to control the volumes and strength of these wastes in order to prevent polluting materials from gaining direct access to watercourses.

It is recommended that all affected municipalities enact and enforce sewer use bylaws to prevent industrial pollution problems. Industries discharging treated wastes and process waters directly to watercourses in the basin should implement waste treatment necessary to meet water quality objectives as outlined in this report.

11 Rural oriented management practices for water quality improvement include limiting fertilizer application rates, channel protection programs, restricting free access of cattle to streams, control of farm waste discharges, particularly from intensive feedlot operations, and control of illegal septic tank connections to drains. Surface runoff to streams from fertilized land is a significant diffuse source of nutrients which contribute to excessive aquatic weed growth. Although accurate statistical information is not available, fertilization of cropland beyond recommended rates was found to be a general practice in the basin.

It is therefore recommended that fertilizer application rates be limited to those recommended by the Ontario Ministry of Agriculture and Food, using services such as those at the University of Guelph for determining appropriate rates. Individual and group activity by the agricultural community and the active support of government agencies is important to implement this practice.

12 A program of restricting free access of livestock to streams should be commenced. It is recommended that the Ontario Department of Agriculture and Food take the lead role in undertaking detailed study of the implications of such a program to farmers, of the best methods such as fencing or vegetative barriers, and of the feasibility of provincial subsidies to encourage such a program.
13 It is recommended that increased environmental surveillance and enforcement be undertaken by appropriate government agencies to control farm waste discharges, particularly from intensive feedlot operations, and illegal septic tank connections to municipal drains.
14 It is recommended that channel protection programs as described in this report be implemented, with initial emphasis on areas of greatest need which should be identified in detail by appropriate government agencies.
15 Recommendations 11 to 14 are generally relevant to the entire watershed; however, particular attention is drawn to headwater areas, where the need to maintain streamflows at the best possible quality and quantity is especially important. Any lessening of flows and stream quality in these areas will aggravate downstream problems.

Rural oriented management practices and conservation practices should be applied with special rigor in headwater areas, and municipalities in these areas must pay special attention to sewage disposal practices to safeguard both local and downstream water uses.

16 It is recommended that resolution of water quality problems in existing reservoirs be achieved by the two conservation authorities through appropriate combinations of bottom draw, destratification, algae control, disinfection of swimming areas, or modified operating policies as outlined in this report for each reservoir.
17 In evaluating water management options, the assumption was made that, as specified in operation manuals, discharges from Wildwood and Pittock reservoirs would be maintained at minimum rates of 40 cfs and 15 cfs respectively for flow augmentation, and that Fanshawe Dam would be operated on a flow- through basis during low flow periods. An analysis of historical flow data indicated that these rates of flow have generally been maintained on a monthly basis, but that on a daily basis, flows have been less than specified for significant periods.

Accordingly, it is recommended that these reservoirs be operated in such a manner as to ensure the maintenance of the specified minimum flows on a daily basis. It is also recommended that there be close liaison between the Ministry of Natural Resources and the Ministry of the Environment to ascertain if alterations to these operating schedules would optimize the use of existing reservoirs for flow augmentation, without adversely affecting other uses.

18 Water based recreation relates largely to existing and proposed reservoirs. Improved water quality will enhance recreational use of streams, but this use is restricted by limited public access.

Although a significant increase in recreational use of existing reservoirs is not practical without jeopardizing their primary use for flood control and flow augmentation, it is recommended that the Upper Thames River Conservation Authority and the Ministry of Natural Resources undertake a detailed computer analysis to determine what modifications of reservoir operating practices would optimize their flood control and flow augmentation use and enhance their recreational use potential.

19 Channel erosion problems in the lower watershed below Chatham are presently the subject of a $7 million streambank and dike stabilization and rehabilitation project.

It is recommended that a program of corrective action concerning bank erosion from Chatham, upstream as far as Delaware, should be initiated by the Lower Thames Valley Conservation Authority in line with the recommendations in the 1971 report by James F. MacLaren Limited entitled "Flood And Erosion Control Works On The Lower Thames River From Chatham To Delaware".

20 Soil erosion control programs including strip cropping, crop rotation, diversion terraces, grassed waterways and vegetative buffer zones or reforestation should be implemented throughout the watershed, with initial emphasis on areas that should be identified by staff of the Ministries of Agriculture and Food, Natural Resources, and Environment.
21 It is recommended that environmental impact assessments of land drainage proposals be undertaken to screen out or modify proposals which would damage the environment and that selected wetlands of ecological importance, such as the Zorra swamp, be protected from further drainage.
22 Prevention of water supply interference and ground water quality impairment, rather than remedial action after the problem has occurred, should be practised using procedures detailed in chapter 7 of this report.
23 To overcome communication and co-ordination problems relating to water management in the basin, and to implement planning on a watershed basis, a joint committee of government agencies and other appropriate bodies should be established. The committee should include representatives of the Ministries of Agriculture and Food, Environment, Housing, Natural Resources, and Treasury, Economics and Intergovernmental Affairs, the two conservation authorities, municipalities, citizen groups and the agricultural community.
24 Another aspect of communication and co-ordination, raised during the Public Consultation Program, related to the division of the watershed into two conservation authorities, because of the interrelationships of water resource problems and solutions in the upper and lower watershed, and in order to further the basin wide approach to water management advocated in this report...

It is recommended that consideration be given to the amalgamation of the Upper Thames River Conservation Authority and the Lower Thames Valley Conservation Authority into a single authority.

25 Regulation of new floodplain development is a vital aspect of flood control. Controls of such development have already been implemented in some areas of the watershed.

It is recommended that further controls of floodplain development under the planning act and through regulations administered by the conservation authorities be developed.

26 Flood warning, which can be an effective measure in reducing flood losses through temporary evacuation of people and damageable goods, requires an efficient flood warning system to be successful. It is recommended that the Conservation Authorities Branch and The Conservation Authorities consider the development of an improved flood warning system.
27 For long term flood control, flow augmentation and erosion control benefits, it is recommended that sound conservation measures such as reforestation, sound agricultural tillage, use of appropriate ground cover, and preservation of water retaining areas be encouraged and implemented. Reforestation and establishment of shrub cover along streambanks should be directed to areas where they would specifically aid in erosion control, streambank stabilization, and the improvement of fish habitats.
28 It is recommended that municipalities and government agencies encourage and enforce careful construction practices during drainage ditch installations and other construction activities in and along watercourses.
29 It is recommended that development in areas of sand and gravel not be permitted to hinder infiltration or to degrade the quality of infiltrating water. This is particularly true of areas of municipal water supply, such as the Woodstock well field. In addition, areas providing significant baseflow such as the Harrington-Lakeside moraine should be protected.


Thames River Implementation Committee (TRIC)

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Last Updated: Thursday, January 14, 2010 08:57:56 PM