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More than 50 years ago, Ontario recognized the importance of watershed planning and established conservation authorities whose functions were to promote water management on a watershed basis. Although flooding and erosion issues had dominated water management for many decades in Canada, we have now recognized that water management has many other objectives such as water quality, ecological health, terrestrial and aquatic resources, etc. In order to manage our water resources effectively, we should apply an ecosystem approach in water management. The logical sequence of water management planning should be watershed plans, subwatershed plans, and site plans and these plans should be integrated with municipal land use planning process. This chapter introduces the concept and framework of water management planning and presents two water management studies.



Before we discuss about water management planning, we have to understand the importance of ecosystem in water management planning. An ecosystem comprises both biological (e.g., bugs, fish, animals, etc.) and physical components (e.g., air, water, soil, etc.) and their interactions characterize the ecosystem. Ideally, an ecosystem should be almost self-contained. In reality, all ecosystems interact with the surrounding environment. In order to study an ecosystem, we try to delineate ecosystem so interactions with outside environment are minimized.

A water ecosystem is all water and living organisms and their interaction and relationship. However, the land adjacent to water also plays an importance role in a water ecosystem. For instance, trees along a watercourse provide shade and food to aquatic organisms in the watercourse. Additionally, whatever happens on the land eventually enter the water ecosystem through surface runoff. Thus, watershed planning encompasses both land and water ecosystems.

An ecosystem approach to water management should protect the linkages among biological and physical components of the ecosystem and allow for sustainable development within a watershed. This approach is superior to the traditional river basin planning which focuses on water utilization and water damage reduction. Although we cannot quantify every ecological process in an ecosystem, some qualitative evaluation of cause and effect may allow us to impute the potential impacts due to urbanization.



A watershed is defined as the land area drained by a river and its tributaries. It is used to define the surface water drainage boundary. The concept of watershed originates from surface hydrology where a river is assumed to be affected primarily by its surface drainage area. In fact, both surface and subsurface hydrology define a river and the importance of subsurface hydrology should not be overlooked. For instance, river baseflow is supplied primarily by ground water. However, it is generally assumed that the subsurface watershed be similar to the surface watershed. The following diagram demonstrates an example of watershed, subwatershed, and site boundaries.
The main process in a watershed is the hydrologic cycle which summarizes the movement of water among surface water, air, land, and ground water. This process governs the physical, chemical, and biological characteristics of water ecosystems in a watershed.


Land Use Change

One of the driving forces for water management planning is development pressure. In the Greater Toronto Area, we have seen un-sustainable developments which emphasize maximum economic return rather than sustainable environment. The end result is that residents are faced with degraded natural and social environment. In order to allow sustainable growth in any municipalities, it is important to develop water management plans so future urban development can be allowed without significant harm to the environment. In assessing ecosystem system response to urbanization, the most logical planning boundary is the watershed.

Natural Watershed

Urbanized Watershed


Urban Rehabilitation

Fully urbanized municipalities also may be interested in water management planning which focuses on rehabilitation of degraded urban environment and sustainable re-development. In urban retrofit planning, the primary planning boundary should also be watershed. Sometimes, natural watershed boundary in fully urbanized area may be altered and a watershed may be delineated with respect to sewershed boundary.



Water plans use an integrated approach to minimize impacts associated with human land use and enhance the natural environment wherever possible. Ultimately, this approach protects the resource, allows for more informed planning decisions, involves stakeholders, speeds up approvals, and saves money to all involved.


Watershed Management Plan

It is essential that water management plan be prepared on a watershed basis. The logical sequence of water management plan should be watershed plan, subwatershed plan, and site plan. The relationships between these planning levels are illustrated in the following diagram.

A watershed plan is:

  • A document for the management of water, land/water interactions, aquatic and terrestrial life and resources. It is often initiated either by local municipalities or conservation authorities who recognize either an existing or potential deterioration of the environment due to existing and future urban development. Funding may be shared between municipalities, conservation authorities, provincial ministries, and developers.
  • Its goal is to protect, enhance, and rehabilitate water resources in relation to existing or changing land use.
  • The fundamental process for water management is the hydrologic cycle that integrates physical, chemical, and biological processes of the ecosystem in the watershed.
  • This plan provides management goals, objectives, control targets, and environmental constraints and this information should be integrated with either land use or rehabilitation planning and decisions.
  • One of key components of watershed planning is public involvement and consultation.

The first step of watershed planning process is to develop water management goals and objectives. The differences between goals and objectives are sometimes confusing. My opinion is that there should be only one watershed goal and a number of water management objectives. The water management goal for a watershed may be to protect and sustain whatever is essential to the watershed health and rehabilitate whatever is degraded.

In order to reach the water management goal, we may need to achieve a number of objectives relating to water quantity and quality, ecological health, sustainable development, and socio-economic enhancement. Some of these objectives may be complementary or competitive. Thus, some compromises and tradeoffs may be necessary to find the best water management policies and strategies. For instance, conservation of green space is competing with urban residential development. A compromise may be that the essential green space is preserved while urban residential development may be allowed in less significant green space areas.

Achievement of water management objectives should be measured with respect to indicators and/or parameters. For instance, the Toronto Wet Weather Study has 12 objectives and each objective is measured by its respective indicators and/or parameters. Table 1 shows some examples of the criteria/indicators in the Toronto Study.

Healthy Aquatic Communities Representative aquatic communities Indicator species/communities
Reduction of fish advisories Contaminant guidelines Sportfish tissue contaminants
Reduction of erosion impacts on habitats and property In-stream erosion potential In-stream erosion index
Rehabilitation of natural hydrologic cycle Water budget Total runoff volume
Re-establishment and rehabilitation of natural features In-stream corridors Barriers (structures, velocity/depth, chemical)
Virtual elimination of toxics through pollution prevention Spill prevention/emergency response Number of reported spills
Meeting Federal, provincial, municipal sediment and water quality guidelines E. Coli guidelines 5 day geometric mean
Elimination of Sanitary Sewer Discharges CSO/SSO overflows Number of overflows
Improved water quality for body contact recreation Beach closures Number of days closed
Improved aesthetics Algae, turbidity, odour, fish kills Number of complaints
Reduction of basement flooding Reported incidents Number of complaints
Reduction of infiltration/inflow Sewer flows Dry weather flow (sanitary/storm)
Protection of life/property from flooding Protection of life/property Ratio of site protected/site identified
Table 1: Examples of the objectives, indicators and parameters of the Toronto study

Assessment of existing watershed conditions requires ecological mapping of the watershed features (e.g., geology, ESA, topography, land use, rivers and lakes, fishery, etc.). Such a task can be handled efficiently with the use of Geographic Information System. However, if sufficient and compatible digital data of the watershed features are not readily available, this may be the most expensive and time-consuming task of the whole planning process. Nevertheless, these maps will assist the identification of sensitive areas for protection and less sensitive areas for development.

Watershed wide policy (Fig. 1) can be developed by analyzing the ecological impacts of various development scenarios and evaluate their achievement of watershed objectives. Comparison of alternative development scenarios requires that relative weights be assigned to watershed objectives and a consistent rating system for various levels of achievement be adopted. The final development scenario and the associated watershed wide policy (which maximizes the overall achievement of watershed objectives) will be recommended.

  • Will take a broad ecosystem approach to water, water related natural features, terrestiral resources, fisheries, water dependencies/linkages and valley/open space systems.
  • Will provide watershed wide policy and direction for:
    1. Ecological integrity and carrying capacity
    2. The protection of valley system and green space planning
    3. The management of water quantity and quality
    4. Acquifer and ground water management
    5. Fisheries management
    6. Rehabilitation/enhancement programs
    7. A framework for implementation of watershed policies and programs
    8. Regional opportunities and constraints
    9. Document servicing needs/availability of water/sewage
  • Will delineate subwatershed planning areas
  • Present target, goal and objectives for subwatershed
Plan recommendations to be input to official plans

The watershed planning process will also delineate subwatershed planning areas, set the associated control target, goal and objectives, and the priority of subwatershed planning study.

The whole watershed planning process should involve publics and stakeholders in every step so the final watershed plan can be acceptable to most people in the watershed. As discussed before, compromises and tradeoffs are necessary to maximize the overall achievement of watershed objectives.

Where a watershed plan has been prepared, all land use planning decisions should be carried out in accordance with the recommendations of the watershed management plan. In Ontario, the primary planning document in the municipal land use planning process is the official plan. It sets the municipality's goals and objectives for land uses within its jurisdiction and provides specific policy direction which guides land development in accordance with provincial policies and guidelines. An official plan can reflect the broad directions, goals and targets established in the water management plan. The relationship between water management planning and land use process is illustrated in the following flow diagram.

Municipal Land Use Process


Stormwater Management | Watershed Management
Municipal Stormwater Management | Hydrologic Systems | Erosion / Sediment Control