Watershed management provides for a rational and scientific approach to natural systems conservation, restoration and use. The information collected from years of monitoring coupled with community knowledge is used as the basis of watershed and fisheries management planning. These plans provide recommended actions that will guide watershed management for current and future generations.

Watershed management actions include tools and programs related to protecting people and property (flood forecasting and warning), improving watershed health and monitoring overall watershed conditions in terms of the following topics: groundwater quantity and quality, surface water quantity and quality, aquatic resources and terrestrial resources.

GRCA Watershed Monitoring Plan - 2014 

Flood Forecasting and Warning

The Ganaraska Region Conservation Authority maintains a flood forecasting and warning system. The purpose of the system is to reduce risk to life and damage to property by providing local agencies and the public with advanced notice, information and advice so that they can respond to potential flooding and flood emergencies.

A flood is defined as a situation where water levels in a watercourse exceed the channel banks. Flooding in Ontario is a fairly common occurrence. The greatest flood in recent memory hit the Port Hope area in March of 1980 when the Ganaraska River flowed over its banks as a result of heavy rainfall on a dense snow pack. Rain on snow is not the only type of event that can cause flooding. Hurricanes moving north from the tropics can carry heavy rainfall into Ontario commonly resulting in flooding, particularly in larger watersheds. High local rainfall associated with severe thunderstorms can cause flooding usually associated with smaller watersheds. Winter ice jams associated with spring break up have also resulted in severe flooding situations. High water levels and/or storm surges on Lake Ontario can also result in flooding along the lakeshore.


The Ganaraska Region Conservation Authority operates its daily planning cycle to monitor, on an ongoing basis, weather forecasts, radar and watershed conditions at locations across the watershed. Water level and related information is remotely collected through an extensive network of stream gauges, rain gauges, snow course sites and staff gauges (monitoring network). Our extensive knowledge and historic data on the watershed's responses to extreme weather and conditions in our watersheds is used to develop a flood forecast. 

When conditions warrant, GRCA will communicate with local agencies (municipalities, emergency services, local media, school boards and government agencies) issuing flood messages following a standard format used by all Conservation Authorities. During spring snowmelt or severe storms, the Conservation Authority estimates the severity, location, and timing of possible flooding, and provides these forecasts to local agencies using one of the following message formats:

Watershed Conditions Statement - Water Safety
- High flows, unsafe banks, melting ice or other factors that could be dangerous for recreational users such as anglers, canoeists, hikers, children, pets, etc. Flooding is not expected.

Watershed Conditions Statement - Flood Outlook - Early notice of the potential for flooding based on weather forecasts calling for heavy rain, snow melt, high wind or other conditions that could lead to high runoff, cause ice jams, lakeshore flooding or erosion.

Flood Watch – Flooding is possible in specific watercourses or municipalities. Municipalities, emergency services and individual landowners in flood-prone areas should prepare.

Flood Warning – Flooding is imminent or already occurring in specific watercourses or municipalities.


A flood event may be defined as a sudden increase in watercourse levels resulting from the occurrence of precipitation, snowmelt, or a combination of the two. The severity of flood events can range from minor increases in creek levels (resulting in “hazardous creek conditions”), to extreme flood conditions (posing a risk to life and property). These various types of events, and the corresponding flood response activities, are described in the Ganaraska Region Conservation Authority’s Flood Contingency Plan.


To find out if a flood message has been issued please consult the following:

  • Radio, television and daily media will air flood messages
  • Go to the GRCA website at www.grca.on.ca
  • Call the GRCA directly at 905-885-8173
  • Contact your local municipality

If you have an urgent flooding concern, please contact your local municipality. In case of a flood emergency, please contact our Flood Duty Officer at 289-251-2094 or 289-251-1010.


Wilmot Creek (3rd Concession, Clarington) Water Level, Rainfall
Wilmot Creek (7th Concession, Clarington) Water Level, Water and Air Temperature
Graham Creek (Newcastle) Water Level and Water Temperature
Ganaraska River (Sylvan Glen) Water Level
Ganaraska River (Osaca) Water Level
Northwest Ganaraska River (Osaca) Water Level, Water and Air Temperature
Cobourg Creek (Cobourg) Water Level, Rainfall, Water and Air Temperature
Cobourg Creek West Branch (Telephone Rd.) Water Level, Water and Air Temperature
Baltimore Creek (Baltimore) Water Level, Rainfall, Wind Speed and Direction, Water and Air Temperature
Ganaraska Forest Centre Rainfall, Snowfall, Wind Speed and Direction, Air Temperature
GRCA Main Office Rainfall, Relative Humidity, Wind Speed and Direction, Air Temperature

Groundwater Monitoring
The Ganaraska Region Conservation Authority (GRCA) has developed and currently implements a comprehensive groundwater program. The program consists of several projects and initiatives aimed at enhancing the understanding, protection, and management of groundwater resources within the authority’s watersheds. These projects include groundwater monitoring, modeling, surface water and groundwater interaction, as well as data collection and technical support activities. Data collected and analyzed through the groundwater programs is used in local planning initiatives including drinking water source protection, watershed plans and fisheries management plans.

As part of the GRCA watershed wide integrated monitoring program, the main objective of the groundwater monitoring project is to quantify groundwater level fluctuations, groundwater flow directions and gradients, monitor groundwater quality at selected locations, and record changes over time. The groundwater monitoring project includes the following:

Provincial Groundwater Monitoring Network (PGMN) Wells

A number of recent studies conducted in Ontario have suggested that groundwater resources are under increasing stress from factors that affect both water quality and quantity. Long-term integrated groundwater monitoring programs are needed to address these issues. In 2001, the Ontario’s Ministry of the Environment (MOE) initiated the development of a Provincial Groundwater Monitoring Network (PGMN) in partnership with conservation authorities and a number of municipalities across the province. The PGMN program focuses on monitoring of water level and water quality in selected and instrumented monitoring wells within each conservation authority. Data generated from this network provides supporting background information for groundwater resource management areas such as drought response, scientific modeling, water policy development, and land use planning.

The GRCA has been actively involved with the PGMN program since September 2001. PGMN monitoring wells were selected to monitor ambient conditions in shallow and deep aquifer systems. To date, 17 wells across the GRCA watersheds have been incorporated into the network, 15 of which are instrumented with automated water level monitoring and telemetry equipment, and 2 with manual download stations. Dedicated water quality sampling pumps were installed in 11 wells. Five annual rounds of groundwater samples were also collected from the majority of the wells and analyzed for water quality parameters. The PGMN wells provide necessary baseline data and aid the GRCA in making informed land use planning and sustainable groundwater management strategies. 

Base Flow Monitoring

The groundwater system supports aquatic species and their habitats by providing baseflow to the rivers and creeks. Baseflow is defined as that portion of the total flow within a stream section that is derived exclusively from groundwater discharge. Following a period of little or no precipitation, essentially all flow within a river system can be baseflow, notwithstanding possible anthropogenic inputs (e.g. such as the release of water from various sources of surface storage, ponds, and storm water sewers). Baseflow contributes to habitat conditions that support a healthy aquatic ecosystem. Changes to the quantity and quality of groundwater discharge can affect the aquatic ecosystem. Monitoring of low flow in local streams is particularly important for the management of water resources since demand for water usually increases during dry weather. As a result, streamflow may approach the minimum requirements to sustain ecological or water quality functions. Groundwater discharge is often concentrated in particular areas as a result of changes in topography, geology, and the nature of the groundwater flow regime.

GRCA technical staff and students monitor baseflow during summer seasons when precipitation is expected to be low. Suitable sites selected for the spotflow monitoring are intended to be generally representative of entire watershed or smaller catchments in a subwatershed.

Streambed Piezometers

To assess surface water and groundwater interactions within the GRCA watersheds, a streambed monitoring and data collection program was initiated during the 2005 monitoring season. This program focused on monitoring surface water and groundwater vertical hydraulic gradients using streambed piezometers installed in selected locations of high water table elevation and potential groundwater discharge. Several steps have been taken by GRCA staff to select proper locations for piezometers installation and monitoring. These included review of surficial geology maps, temperature monitoring data, fish communities’ distribution, and thermography survey maps.

Data collected from 16 streambed piezometers as well as analysis of climate data, baseflow data, fish communities, and temperature data allow GRCA staff to quantify surface water and groundwater interaction.

Low Water Response

Fresh water is a natural resource crucial to the economic and environmental well being of Ontario. Water supports almost all aspects of human activity including health, industrial development, and recreation. Because water is critical to so much of our activity, it is managed from several perspectives and by many jurisdictions, groups and individuals.

The Ontario Low Water Response program is intended to ensure provincial preparedness, to assist in coordination and to support local response in the event of a drought.

The GRCA monitors precipitation and stream flows throughout the year using the hydrometric network to make comparisons with historic data in support of the Ontario Low Water Response Program. This comparison allows the GRCA to clearly identify when local watersheds enter drought conditions.  

The GRCA administers the Ganaraska Low Water Response Team, which has been created to coordinate the activities of water management agencies with respect to dissemination of information, analysis, and response to water events including drought. 

August 2016: Drought conditions are affecting much of Southern Ontario this summer including the Ganaraska Region where only 45% of the normal rainfall has fallen since April 1st. With the lack of rainfall, farmers and homeowners need to use water to sustain crops and gardens. However, over-consumption of this precious resource can lead to more severe impacts should the dry conditions continue. Reduced crop yields and suffering vegetable gardens are just some of the possible impacts. With greater demand from surface water and groundwater sources, water levels are declining below normal. As this happens, organisms that live in the streams experience warmer temperatures, reduced flow and habitat area, and increased concentrations of nutrients and contamination are possible. Shallow groundwater wells can become dry or fail to supply enough water to homes and businesses. This is the time to review how we use water and what conservation practises we can implement to reduce demand for water. This short term initiative will help to conserve our water resources and reduce the overall impact to the ecosystem until more consistent rainfall returns.

Follow these guidelines to conserve and use water wisely:

  • Leave lawns to go dormant, they will recover in the late summer as the sun's intensity diminishes
  • Use drought tolerant plants in gardens as much as possible
  • When watering gardens, soak the soil deeply to increase soil moisture and promote deep root growth
  • Water up to 1" or 25mm per week including rainfall
  • Try to avoid watering during the day when evaporation is highest, early morning or at night is the best time
  • Water on alternate days and use alternate sources (wherever possible) to spread out the impact of water takings
  • Make use of water storage (e.g. rain barrels, cisterns, off-line ponds)
  • Observe water conservation by-laws and encourage neighbors to comply 

Groundwater Indicator for Low Water Response Program

The Ontario Low Water Response (OLWR) program relies on precipitation and stream flow indicators to evaluate low water conditions in watersheds across the province. These indicators provide water managers with objective information on the severity of low water conditions that may require a response to reduce water demand. Low water conditions are characterized as one of three levels of increasing intensity: Level I (Conservation), Level II (Conservation, Restriction) and Level III (Conservation, Restriction, and Regulation).

The OLWR program has identified the need for a groundwater indicator to be added to the program and used in conjunction with the rainfall and stream flow indicators.

7 PGMN wells have been selected and tested for their suitability to the OLWR program.

YPDT- CAMC Groundwater Management Study and Modeling

The Oak Ridges Moraine (ORM) is an extensive stratified sediment complex (60 km long and 5 to 20 km wide) stretching across southern Ontario from the vicinity of Trent River in the east to the Niagara Escarpment in the west. It is recognized as a regional groundwater recharge area, providing a source of groundwater to numerous aquifers and to the streams having headwaters on the flanks of the moraine including the Ganaraska River, Wilmot Creek, and Cobourg Creek watersheds within the GRCA. The York, Peel, Durham, Toronto – Conservation Authorities Moraine Coalition (YPDT – CAMC) Group was formed through the recognition of the natural, social, and economic importance of this feature.

The YPDT –CAMC Groundwater Management Study is being conducted to provide a hydrogeological analysis suitable for water resources management encompassing the watersheds emanating from the ORM. The project reflects the interests of four municipalities and nine conservation authorities that are working together to better understand groundwater issues across the ORM area. It is the goal of the partnered agencies that the project is maintained as a long term initiative in order to continually build on the early development, encompass new data, and foster constructive improvements to the existing work. The five key strategic components of the YPDT – CAMC are:

1.    Policy framework development.
2.    Data collection and management.
3.    Technical analysis/studies.
4.    Implementation framework.
5.    Monitoring and evaluation.

As part of the YPDT – CAMC work, a regional-scale three dimensional geologic model and several MODFLOW groundwater flow models have been developed that span the entire Oak Ridges Moraine (ORM) and the surrounding area. The primary objective of these modeling efforts is to develop tools to help understand the geology and hydrogeology of the ORM and to support the many land use decisions being made in the area. The most extensive of these models is the regional MODFLOW model which was built on a SiteFX / ViewLog platform. The regional model is based on 5 hydrostratigraphic layers with a nominal cell size of 240 by 240 meters and covers an area encompassing all watersheds that originate on the Oak Ridges Moraine including the GRCA 5 major and 4 groups of watersheds. The model layers represent the major aquifer and aquitard units in the overburden and upper bedrock formations.

The YPDT – CAMC program continues to update the geological and hydrogeological understanding of the region and subsequently to refine the groundwater flow models. The GRCA staff work with the YPDT – CAMC team to refine and build on the existing understanding of the geological layers and groundwater flow system within the GRCA watersheds. The YPDT-CAMC geology and groundwater work currently in progress and includes the following tasks:

1.    Maintaining and enhancing the database (e.g. adding new high quality wells, conversion from Access to SQL... etc).
2.    Refining the geological layers based on new drilling information that is being collected by the partners from various projects.
3.    Ensuring more effective access by partner agencies to the database.
4.    Assisting with the application of numerical groundwater flow models to local site problems and investigations.
5.    Liaising with the consulting community to ensure broader utilization of the program's data, interpretive geological layers, and modeling files.

The updated and verified database, hydrostratigraphic model layers (geologic model), and groundwater flow model represents significant technical products for the GRCA groundwater program. These products, together with surface water modeling, are used as the technical foundations in many areas including management and protection of water resources, watershed planning studies, other studies and initiatives.

Water Quality Monitoring

The GRCA operates a number of surface water quality monitoring programs designed to understand the water quality of our watersheds, determination of trends in water quality, and provide long term monitoring of watershed health. The data collected from these programs is analyzed and used in watershed management through planning, fisheries management planning, source water protection planning and water quality reporting.

The Ministry of the Environment (MOE) operates the Provincial Water Quality Monitoring Network (PWQMN). Conservation Authorities such as the GRCA and other agencies are partners in the PWQMN by collecting samples and sending them to the MOE lab.

The GRCA has completed sampling throughout its jurisdiction to characterize surface water quality for all of its watersheds.  Current programs are focusing on characterizing water quality during low flow periods when watershed health is experiencing the most stress and during high flows when the water quality is typically degraded.

Typical parameters that are measured in these water quality programs include temperature, pH, conductivity, turbidity, suspended solids, major ions, nutrients, metals and bacteria

Wetland Monitoring

Water Quality Monitoring

Wetlands provide environmental functions that are important to both humans and wildlife.  These functions may vary among wetlands depending on the size of the wetland, its soils, plant community, and position in the landscape.  For example, wetlands found in upper watersheds are very important as areas of groundwater recharge, flood retention, and maintenance of base flow in streams.

The GRCA is a partner in the Durham Region Coastal Wetland Monitoring Project, which is designed to utilize standardized monitoring protocols to assess the long term health of the wetland systems.  Monitoring efforts are focused on all aspects of wetland health, including water level, water quality, sediments, plants, and macroinvertebrate, amphibian and bird communities.

Coastal wetlands have unique functions that are performed naturally:

Interception and slowing of watershed run-off before it enters the lake allowing:

-  Settlementation and retention of sediments and contaminants (such as heavy metals and PCBs).
-  Reductions of excess nutrients as wetland plants absorb nitrogen and phosphorus and use them for growth.
-  Provision of habitat for microbe and invertebrate species, thereby providing the foundation for a complex food web.  These food sources, along with the wetland plants, in turn support a wide variety of fish, reptile, amphibian, mammal, and bird species.

These natural wetland functions translate into important societal values:

-  Opportunities for recreational activities including canoeing, fishing, hunting, wildlife viewing, and photography.
-  Protection of shoreline properties from the potentially destructive forces of erosion.
-  Improvement of water quality for the millions of people in Canada and the United States who rely on the Great Lakes for their drinking water.

Watershed Planning

A watershed is an area of land that drains water to a particular point, which in the Ganaraska Region Conservation Authority watersheds is Lake Ontario.  The purpose of watershed planning is to develop locally driven plans that will create a framework to guide the conservation, management, rehabilitation, and enhancement of the watersheds and their resources.  This process is needed for sound land use planning and is required under the provincial Oak Ridges Moraine Conservation Plan.  The topics covered within a watershed plan include groundwater quantity and quality, surface water quantity and quality, terrestrial natural heritage, acquatic habitat and species, public health and well being, and community heritage.

In 2009, the Cobourg Creek Watershed Plan was finalized.  The Cobourg Creek Technical Review Committee and Community Advisory Committee have provided valuable review and input into the watershed plan. Two key documents have been created through this initiative, the Cobourg Creek Background Document: Abiotic, Biotic and Cultural Features and the Cobourg Creek Watershed Plan.

In 2010, the Ganaraska River Watershed Plan, Wilmot Creek Watershed Plan, Graham Creek Watershed Plan, and the Lovekin Creek, Bouchette Point Creek and Port Granby Creek Watershed Plan were all finalized.  Each of these watersheds also engaged a Technical Review Committee and Community Advisory Committee that provided valuable reviews and inputs into the watershed plans.

Each of these initiatives is supported by a Background Document: Abiotic, Biotic and Cultural Features.
Wilmot Creek Background Report
Graham Creek Background Report
Lovekin Creek, Bouchette Point Creek and Port Granby Creek Background Report

The next step after the development of the watershed plans is plan implementation. This step is seeing the recommended mangement actions realized throughout the watersheds. Plan implementation occurs through the many partnerships between the Ganaraska Region Conservation Authority, local municipalities, agencies, stakeholders and residents.

To learn more about watershed planning , or to become involved in plan implementation please contact the Ganaraska Region Conservation Authority at 905.885.8173 or

Private Wells and Permit To Take Water (PTTW)

Local Private Water Supply Wells

The majority of the water supplies in the GRCA watersheds are private wells used as domestic water sources. These domestic wells are located throughout the area, except where municipal water systems are available. Many of these wells supply water to permanent residents, cottages, and summer homes in rural areas.  Some wells are also used for agricultural purposes including livestock watering and irrigation, and others are also used for commercial and industrial purposes.

The GRCA Watershed Hydrogeologist provides technical support to the watersheds residents in caring and maintaining their wells in a good working order. This is done by conducting site visits, answering well owner’s questions, referring water sampling to Health Units and Departments, providing educational materials and conducting safe groundwater seminars across the GRCA.

Safe Groundwater Seminars

The GRCA, in partnership with the local municipalities and local Health Units/Departments, organizes Safe Groundwater Seminars across its jurisdictions from time to time. The seminars are designed to provide information and educational materials to home owners who rely on private wells as water supply systems, who have septic systems.  The seminars are presented in partnership with public agencies and are aimed to assist and educate residents of rural areas within GRCA watersheds. GRCA also invites licensed local water well contactors and consultants to participate in these seminars with displays showing equipment and services available to local area residents.

PTTW Applications and Planning Reviews

Part of the Watershed Hydrogeologist responsibilities includes the review of planning, development, and land use change applications within the GRCA watersheds as they relate to the groundwater regime. It also includes review of technical reports and evaluates potential hydrogeological and groundwater resources impacts of proposed and existing water taking permits. The GRCA has a technical team organized to respond to the Ministry of the Environment (MOE) on all of the submitted Permit To Take Water (PTTW) applications (new applications and renewal), which are located within the authority’s jurisdictions. Technical responses to MOE are normally done in consultation with the local municipalities.

Township of Alnwick Haldimand Township of Cavan Monaghan Clarington Town of Cobourg Region of Durham Hamilton Township Port Hope City of Kawartha Lakes Conservation Ontario
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