Source Water Protection

Image of the 19 Source Protection Regions (SPRs) and Source Protection Areas (SPAs) in Ontario (Conservation Ontario, 2022). Visit the Map link here for a higher resolution image.

Overview

Spurred mainly by the Walkerton Tragedy in May of 2000, where 2,500 residents of the town fell ill due to ingesting high levels of E.coli bacteria and 7 individuals died due to poor monitoring and maintenance of the drinking water system, the province (Scarfone, 2020) took major overhauling actions to ensure Ontarians drinking water was adequately protected.

Following an inquiry into the Walkerton event, Justice, O'Connor at the time made over 120 recommendations to better protect the province's drinking water, which have now been implemented and are the foundation of the province's drinking water protection framework. The first of these recommendations was that drinking water should be protected by developing watershed-based source water protection plans, which have been in place since 2006 with the adoption of the Clean Water Act (Government of Ontario, 2021)

Source Water Protection in Ontario

Since the Clean Water Act, 2006 was adopted within the province the original recommendations of the "Walkerton Inquiry" were able to begin to be implemented. The legislation required municipalities protect their drinking water sources and supplies through prevention by developing collaborative large-scale watershed-based source protection plans or source water protection (SWPP) based on monitoring results and the latest science. When the Clean Water Act was first established the province paid for the cost of developing the preliminary SWPPs.

Under the Clean Water Act the legislation describes newly developed source water protection areas and source water protection regions.

• Source Protection Region (SPR): Encompass one or more source protection areas (ex. Credit Valley-Toronto and Region-Central Lake or simply the CTC Region).
• Source Protection Area (SPA): Smaller geographic areas generally based on the watershed boundaries of Ontario's 36 Conservation Authorities

Ontario’s Clean Water Act, 2006 is the primary piece of legislation within the province to ensure that there is a multi-barrier approach to ensure not only clean and safe drinking water, but by ensuring usage is sustainable and protects lakes, rivers, wells and other major sources of freshwater for ~14.5 million residents (Photo Source: Conservation Ontario, 2016)

Under the Clean Water Act local multi-stakeholder source protection committees were developed for each region. Each committee is comprised on the region's leading researchers, professionals and technical personnel that help identify significant current and potential future threats to their local municipal drinking water sources. Their job is to regularly meet and develop preventative plans to address identified and theorized threats (Lake Erie Source Protection Region, 2022)

Source Protection Plans (SPP)

Source protection plans (SPPs) contain a number of policies that are locally developed by their local technical committees aimed at protecting existing and future spruces of adequate drinking water sources for impacted municipalities.

The associations who are reporting and implementing SPP policies and progress annually include:

• Conservation Authorities;
• Municipalities;
• Source protection authorities;
• Local health boards;
• Indigenous groups, committees and governments;
• Local businesses
• The Province of Ontario; and,
• Others (Government of Ontario, 2021)

The Source Protection Committee generally uses varied approaches to protect drinking water sources within each SPR/SPA, which can include:

• Prescribed policy instruments (existing provincial approvals such as Environmental Compliance Approvals and Permits To Take Water);
• Requiring any owners/developers present a formalized risk management plan (negotiated individually);
• Specified land use planning;
• Prohibition of activities that may prove detrimental to SPZs; and/or,
• Current outreach and education activities (webinars, town meetings, pamphlets, online education hubs) (CTC SPR, 2019)

Under the Clean Water Act, 2006 a total of 19 SPRs and SPA's have been established across the province. Each of these 19 SPRs/SPAs contain their own local multi-stakeholder source protection committees across the province which have developed 38 local source protection plans. These specialized plans identify various actions to protect over 450 affected municipal drinking water systems (covering 95% of Ontario's population) (Government of Ontario, 2021).

Ultimately, SPPs are plans to help reduce or eliminate significant drinking water threats within its associated zone/area. These drinking water threats are listed in the following and the SPPS have policies place which must also be enforced. These policies when implemented help to both manage and/or prohibit significant threats as a result of various activities to ensure that they cannot pollute or deplete necessary sources of municipal drinking water within the zone/area.

A road sign to alert motorists that they are entering a provincially protected Drinking Water Protection Zone (SWPZ) to help raise awareness (Photo Source: Conservation Ontario, 2018)

SPRs & SPAs in Ontario

Listed below are 19 different SPRs and SPAs in Ontario, where you can visit each Region's/Area's dedicated Sourcewater protection website for information on their committee members, recent reports, helpful documents, informational videos and the like:

1. Ausable Bayfield Maitland Valley Source Protection Region
2. Cataraqui Source Protection Area
3. CTC Source Protection Region
4. Essex Region Source Protection Area
5. Greater Sudbury Source Protection Area
6. Halton-Hamilton Source Protection Region
7. Lake Erie Source Protection Region
8. Lakehead Source Protection Area
9. Mattagami Region Source Protection Area
10. Mississippi-Rideau Source protection Region
11. Niagara Peninsula Source Protection Area
12. North Bay-Mattawa Source Protection Area
13. Quinte Region Source Protection Area
14. Raisin-South Nation Source Protection Region
15. Saugeen, Grey Sauble, Northern Bruce Peninsula Source Protection Region
16. Sault Ste. Marie Region Source Protection Area
17. South Georgian Bay Lake Simcoe Source Protection Region
18. Thames-Sydenham Source Protection Region
19. Trent Conservation Coalition Source Protection Region

Source Protection Assessment Reports

Each of the 19 aforementioned SPRs & SPAs has an Assessment Report that acts as a 'living technical document' for that given region. The Assessment report includes:

• Recent research findings and scientific information regarding source water protection;
• A brief overview of each impacted watershed within the SPR/SPA;
• Provides a water budget (which is a way to measure the amount of freshwater water enters, is stored, and leaves a watershed);
• Identifies vulnerable areas near key freshwater sources (municipal wells and intakes);
• Identifies the number of significant threats (agricultural practices, sewage sources, fertilizers, etc.) to water quality near wells and intakes; and,
• Identifies areas that could have varied threat levels (low, moderate, high) (CTC SPR, 2019)

Planning Considerations

Inclusion of the tools and atlas

• Recommendations - refer to SPP (pull from B.C's recommended practices)
• Top lessons and maintenance (setback distances / replacing media)

Talk about pretreatment - filtration before being sent directly to groundwater source (bioretention/swale -> infiltration trench) Online vaults from minor system flows (filter and target specific pollutants) - before infiltration.

When planning any new development within a SPR/SPA its important to follow the following four (4) major Steps before moving forward.

1) Identify and Map Vulnerable Areas

The two major areas of significance that are vulnerable to water/groundwater pollution threats are called Wellhead Protection Areas (WHPAs) and Intake Protection Zones (IPZs). New development must note if any of their proposed activities or future actions will cause potential negative impacts on these important municipal sources of freshwater.

Wellhead Protection Areas (WHPAs)

A Wellhead Protection Area (WHPA) is an area located on the ground surface that denotes a specific zone within a known aquifer where fresh groundwater flows to a pumping well. Any detrimental activities/actions that take place in this zone may contribute to pollutions that can infiltrate into the underlying soil below and in turn contaminate said groundwater source for private and municipal wells alike - hence undertaken in this area may release pollutants that could seep into the soil and contaminate the groundwater used by both domestic and municipals wells. As a result, these areas require high levels of monitoring, protection and enforcement. Accordingly, this area warrants greater protection.

The risk to groundwater quality at the well site is determined by the rate at which a specific pollutant/contaminant can infiltrate and travel to the well and the time it would take to remediate the contaminant from the water supply by trained municipal water operators. If a chemical/contaminant spill were to happen a far distance away from a known well, a follow up assessment will be required, this assessment includes:

• Determining whether the contaminant could reach the well in question and the duration of time it may take to reach it.
• Is the contaminant a human, biological or environmental risk or is it simply an aesthetic nuisance?
• Will the concentration of said contaminant exceed the Canadian Water Quality Guidelines (CWQG) for drinking water standard or the Provincial Water Quality Network's (PWQMN) standard (i.e. chloride levels)?
• Will the current mitigation/treatment protocols currently used be sufficient enough to mitigate/remove the harmful concentration levels of said contaminant from reaching the well?
  • If said mitigation/treatment protocol needs to be amended and time allows a mitigation system can be installed to limit the movement of said chemical to the well or the water treatment process at the receiving Water Treatment Plant (WTP) can be modified to sufficiently decrease the concentrations being received

When it comes to WHPAs once size does not fit all, there are multiple zones that extend in an irregular radius around a well to ensure adequate protection of the source water protection area, which is divided into five (5) zones based upon contaminant travel time within groundwater sources:

1. WHPA-A – an area of 100 metre radius around the wellhead
2. WHPA-B – the zone through which it takes groundwater to travel between two years and the 100 metre distance
3. WHPA-C – the zone through which it takes groundwater to travel between five and two years
4. WHPA-D – the zone through which it takes groundwater to travel between 25 and five years
5. WHPA-E – the area on ground surface through which surface water flows in two hours to a point close to the well. This wellhead protection area is only delineated when studies have shown that surface water can relatively easily seep through the soil and impact the quality of the water at the well. This situation is known as groundwater under the direct influence of surface water, or a GUDI well
   (Halton-Hamilton Source Protection Region, 2010;CTC SPR, 2019)

Vulnerability
As mentioned, WHPAs identify an area on the surface that reflects a zone within the underlying aquifer below where groundwater flows to a well. That said, this area is generally not equal to the total contributing water area that drains towards the well over a given duration of time. This contributing area is the location seen on the surface where water can infiltrate into the soil and still reach the well far away. Due to its distance there may be more urbanization within this expanded area and other contributing contaminants that can pollute the groundwater as it flows to the well. This area generally requires the most protection by the associated SPR/SPA, Conservation Authorities located within the area and subsequent municipalities as it is the area/zone most prone to surface contamination (Halton-Hamilton Source Protection Region, 2010).

Vulnerability for source water is simply calculated by:

1. Determining the amount of time it takes for water to travel through the "unsaturated zone" above the water table; and,
2. Adding that number to the modelled time it takes for groundwater to flow from the water table to the well based on the WHPA zone (EarthFx Incorporated, 2010).

As a result, these surface to well duration periods are categorized as "low" for over 25 years, "medium" for 5 - 25 years, and "high" for 0 - 5 years. These surface to well advection times are categorized as low for over 25 years, medium for 5 to 25 years, and high for 0 to 5 years of travel. After this mapped groundwater vulnerability areas are then overlain on top of current WHPAs A - D to then assign vulnerability scoring between 2 - 10 (lowest - highest vulnerability scores). The location of a potential development site within the WHPA and its vulnerability score are then used to assign the significance of proposed or future potential actions/activities that have been labelled as potential threats to local drinking water sources. These 22 potential threats as laid out by the province can be seen in the table below in this section (Halton-Hamilton Source Protection Region, 2010).

Intake Protection Zones (IPZs)

An Intake Protection Zone (IPZ) is an area that includes both land and surface water around municipalities' intake pipes that lead to a water treatment plant (WTP) and contributes to the municipalities drinking water system and sources. An IPZ on a map delineates where surface water is originating from and how it end up in the municipal water supply. These zones are determined by how far away they are from the intake location and the time it would take to reach it. The resulting size and shape of each of the three (3) zones of a typical IPZ represents either this set distance around the intake or simply the length of time it would take water and potential contaminants from overland flow to reach the intake.

The 3 zones of IPZ are as follows:

1. IPZ‐1: This is the area closest to a municipality's intake pipe and is a set distance which extends one kilometre (Km) upstream and 120 metres onto the shore. IPZ-1 is the most vulnerable to contamination as it is the closest to the intake and allows limited time for dilution to occur to help reduce the concentration of a contaminant released within the zone, this lack of time also doesn't allow municipal water system operators much time to react to this released contamination that is headed towards the municipal intake.
2. IPZ‐2: This area is developed by utilizing both hydrodynamic modelling and a time-of-travel calculation within overland pathways (natural and human-made - i.e. rivers, creeks, swales, storm sewers, etc.) that ultimately lead to and discharge near the municipalities intake(s). Includes both the on and offshore areas where overland flowing water that may be polluted with a concentration of a given number of contaminants would be able to reach the municipal intake within approximately two (2) hours. The 2 hour mark is set as the minimum amount of time to allow municipal water system operators to address a potential contamination concern.
3. IPZ‐3: This area lies outside of IPZ-1 and IPZ-2 and as such contaminants likely could only reach the intake pipe during and/or after a major rainfall/storm event. The size and shape of an IPZ-3 zone is based on associated lakes, streams and other humanmade conveyances that could contribute excess overland flow during an event.
   

(Halton-Hamilton Source Protection Region, 2010; Cataraqui Source Protection Area, 2022)

Vulnerability
The vulnerability of the three IPZs are assigned scores that reflect their susceptibility to allowing contaminants to reach the municipal intake zone and is determined by local knowledge and technical inptu from industry experts, as well as judgment from the SPA/SPZ committee members.

The source vulnerability scores for IPZ-1 and IPZ-2 is based on multiplying the following factors:

• Distance of the intake from shore/boundary
• the depth of the intake from surface water interaction
• historical water quality conditions and previous incidents/concerns at the intake in questions

hydrological and hydrogeological conditions of the surrounding area

• IPZ-1, due to its close proximity to the intake is set at the maximum vulnerability score value
• IPZ-2, considers the above characteristics along with the percentage of its area that is landcover
  • It also considers land characteristics of this land area (soil permeability, slope and direction, [Soil groups|soil types], vegetation coverage, etc.
• IPZ-3 is not provided a vulnerability score due to its setback distance away from intakes. It's perimeter is designated based on nearby lakes and streams that contribute overland flow to the intake
  

(Halton-Hamilton Source Protection Region, 2010; Cataraqui Source Protection Area, 2022)

2) Identify Threats

There are currently 22 listed "threats" that are outlined in the Clean Water Act, 2006. Please see the table below for further details (Government of Ontario, 2021):

Drinking Water Threats

Threat Type	Threat Number & Description
Agricultural
	1. The application of agricultural source material to land
	2. The storage of agricultural source material.
	3. The management of agricultural source material.
	4. The use of land as livestock grazing or pasturing land, an outdoor confinement area or a farm-animal yard.
Residential/Commercial
	5. The application of non-agricultural source material to land.
	6. The handling and storage of non-agricultural source material.
Sewage & Waste
	7. The establishment, operation or maintenance of a waste disposal site within the meaning of Part V of the Environmental Protection Act.
	8. The establishment, operation or maintenance of a system that collects, stores, transmits, treats or disposes of sewage.
Fertilizer & Pesticides
	9. The application of commercial fertilizer to land.
	10. The handling and storage of commercial fertilizer.
	11. The application of pesticide to land.
	12. The handling and storage of pesticide.
Winter Maintenance / [Salt]
	13. The application of road salt.
	14. The handling and storage of road salt.
	15. The storage of snow.
Fuel & Chemicals
	16. The handling and storage of fuel.
	17. The handling and storage of a dense non-aqueous phase liquid.
	18. The handling and storage of an organic solvent.
	19. The management of runoff that contains chemicals used in the de-icing of aircraft
	20. The establishment and operation of a liquid hydrocarbon pipeline. O. Reg. 385/08, s. 3; O. Reg. 206/18, s. 1.
Water Extraction
	21. An activity that takes water from an aquifer or a surface water body without returning the water taken to the same aquifer or surface water body.
	22. An activity that reduces the recharge of an aquifer.

3) Calculate Threat Level

To calculate your threat level before commencing work there are several steps to take to determine how you can mitigate your impact on the local water supply.

1. Find out if you are in a "Vulnerable Area" as listed under the lean Water Act, 2006. To do this use the Source Water Protection Map Atlas Tool that shows based on your location vulnerability mapping and scores within already established and mapped source protection areas in your area.
2. If your development site is in a known vulnerable area, look at the threats table provided above in this section and ensure that you are not conducting any of the 22 listed activities as outlined under Ontario Regulation 287/07 Section 1.1 (1), "Prescribed drinking water threats".
3. After referencing the table if you discover that you will (or may) be conducting one or more of the listed activities then continue forward by contacting your local SPR/SPA (their emails and contact information are listed on their associated websites).

• Your SPR/SPA will be able to determine whether the work you are looking to conduct is deemed either a:
  • Low
  • Medium
  • High
  • Significant threat for your vulnerable area under their jurisdiction. Your SPR/SPA will have listed policies of which you will legally be required to follow based upon your vulnerability scoring which they will be able to point you to (TRCA, 2018; MECP, 2022

You can go into further details learning about the potential risks your work may pose by visiting the MECP's Best practices for source water protection. This webpage set up by the province allows users to still protect freshwater sources and drinking water systems that are not included within an SPP or regulated under the Clean Water Act, 2006. It provides additional information and approaches prospective developers and users can take based upon local soil infiltration rates, groundwater sources in the area, highly vulnerably aquifers, nearby surface water sources, and other potential factors affecting vulnerability.

Below is a table "risk factors" prospective developers (commercial, residential, municipal) should employ that asks eleven (11) questions and a user can rank to determine how at risk a local drinking water source may be given the work they are considering. Anything listed as "High" warrants further information and action to protect the water source (Table adopted from MECP's Best practices for source water protection (MECP, 2022).

Risk Factors - Self Evaluation

Risk questions	Low Risk	Medium Risk	High Risk
How many wells or intakes are located in your area?	None to "a few"	Several	Many
How deep are the wells and are they drilled or dug?	Deep, drilled	Intermediate	Shallow, dug
How deep is the intake and how far is it located from shore?	Deep, far	Intermediate	Shallow, nearshore
What is the vulnerability of your area?	Low vulnerability setting	Moderate vulnerability setting	High vulnerability setting
How sensitive is the population?	Healthy adults only	Typical family or mixed range of ages	Vulnerable populations like the elderly, youth or infants
How many people does the system serve?	A few	Some	Many
How often is the system used?	Occasionally	Seasonally or part time (work hours)	Every day and/or is the only source nearby
What types of activities are located nearby?	Residential	Agricultural	Industrial or Commercial
Any water quality issues? (i.e. algal booms or a boil water advisories, etc.)?	Confirmed none	Possible or Unknown	Confirmed and Present
Are you located in an area where there is pressure for growth? Or are there other water supply and demand issues?	No	Maybe / Unknown	Yes
Is there oversight of the well(s) or intake(s)? For example, licencing, inspections, testing, compliance, and qualified operators.	Yes	Some	None

4) Apply Appropriate Policies

Policies that must be adhered to are based on several factors:

1. The activity itself
2. The are in which the activity will be taking place
3. The vulnerability of the area in question
4. The risks associated with the activity (does the activity result in one of the listed 22 risks occurring or potentially occurring)
5. Other local factors that can increase the vulnerability to a nearby IPZs or WHPAs

For example, as of December of 2021 the CTC SPR that comprises the regions of Peel, Toronto, and Durham had nearly 130 Source Protection Policies in place within their SPP. These policies address 21 of the 22 types of threats prescribed in O.Reg 287 along with two types of local drinking water threats, and include other actions that are considered by the CTC committee as necessary to protect drinking water sources, along with requirements for the need of monitoring being implemented. The CTC SPP also contain policies which require the need for Risk Management Plans (RMPs) dependent on the vulnerability of proposed actions/activities to better manage some drinking water threats (CTC Source Protection Region, 2021)

Site Considerations

Installation type	Depth to high water or bedrock (m)i	Ratio of impervious drainage area to permeable facility footprint area	Native soil infiltration rate (mm/hr)ii	Head (m)iii	Space %iv	Slope %v	Applicable in pollution hotspotsvi	Set backs	Karstvii	Drinking Water Source Protection wellhead protection area time of travel
Rain barrels	Not a constraint	Not applicable	Not a constraint	1	0	NA	Yes	None	Yes	None
Cisterns	Not a constraint	Not applicable	Not a constraint	0	0	0	Yes	None	Yes	None
Roof downspout disconnection	Not a constraint	4:1 or less	Decompaction if < 15 mm/hr	0.5	5 to 20	1 to 5	Yes	Building Foundation	Yes	None
Infiltration trenches or Infiltration chambers	1	5:1 to 20:1	Not a constraint	1 to 2	0 to 1	<15 %	Noix	4m- Building Foundation Underground Utilities, Trees, Drinking Water Wellhead Protection Areas	No	2 yr
Bioretention	1 (infiltrating); Not a constraint (non-infiltrating)	5:1 to 15:1	Decompaction and underdrain recommended if < 15 mm/hr (infiltrating)	1 to 2	5 to 10	0 to 2	No (infiltrating)ix; Yes (non-infiltrating)	4m- Building Foundation Underground Utilities, Trees, Drinking Water Wellhead Protection Areas	No (infiltrating); Yes (non-infiltrating)	2 yr (infiltrating); None (non-infiltrating)
Stormwater planters	Not a constraint	5:1	Not a constraint	1 to 2	2 to 5	0 to 2	No (infiltrating)ix; Yes (non-infiltrating)	Building Foundation, Trees	No (infiltrating); Yes (non-infiltrating)	2 Yr (infiltrating); None (non-infiltrating)
Vegetated filter strips	Not a constraint	4:1 or less	Decompaction if < 15 mm/hr	0 to 1	15 to 20	1 to 5	Noix	None	Yes	None
Permeable pavements	1 (infiltrating); Not applicable (non-infiltrating)	0 to 1:1	Underdrain recommended if < 15 mm/hr (infiltrating)	0.5 to 1	0	1 to 5	No (infiltrating)ix; Yes (non-infiltrating)	4m-Underground Utilities Drinking Water Wellhead Protection Areas	No (infiltrating); Yes (non-infiltrating)	2 Yr (infiltrating); None (non-infiltrating)
Enhanced swales (featuring check dams)	1	5:1 to 10:1	Decompaction if < 15 mm/hr	1 to 3	5 to 15	0.5 to 6	Noix	4m- Building Foundation Underground Utilities	No	2 Yr
Bioswales (Dry swales)	1 (infiltrating); Not applicable (non-infiltrating)	5:1 to 15:1	Decompaction and underdrain recommended if < 15 mm/hr (infiltrating)	1 to 3	5 to 10	0.5 to 6	No (infiltrating)ix; Yes (non-infiltrating)	4m (3m if impermeable liner is used) Building foundation, Underground utilities, Drinking Water Wellhead Protection Areas	No (infiltrating); Yes (non-infiltrating)	2 Yr (infiltrating); None (non-infiltrating)
Exfiltration trenches	1	5:1 to 10:1	Not a constraint	1 to 3	0	< 15%	Noix	4m- Building Foundation Underground Utilities, Trees, Drinking Water Wellhead Protection Areas	No	2 Yr
Stormwater tree trenches	1	5:1 to 15:1	Underdrain recommended if < 15 mm/hr	1 to 2	5 to 10	0 to 2	Noix	4m- Building Foundation Underground Utilities, Drinking Water Wellhead Protection Areas	No	2 yr

Notes
i Minimum depth between the base of the facility and the elevation of the seasonally high water table or top of bedrock
ii Infiltration rate estimates based on measurements of hydraulic conductivity under field saturated conditions at the proposed location and depth of the practice
iii Vertical distance between the inlet and outlet of the LID practice
iv Percent of open pervious land on the site that is required for the LID practice
v Slope at the LID practice location
vi Suitable in pollution hot spots or runoff source areas where land uses or activities have the potential to generate highly contaminated runoff
vii Suitability in areas of karst geologic formations
viii Drinking Water Source Protection wellhead protection area time of travel
ix May be allowed under special circumstances and if appropriate mitigation actions are taken - please contact your local Source Protection Region (SPR) or Source Protection Area (SPA) for further information. You can find your associated SPR/SPA based on your location here and then visit their site here

Design Features

LID BMPs

The drainage area of a river.

An area of land that drains into a river or a lake. The boundary of a watershed is based on the elevation (natural contours) of a landscape.

Any person, agency or group who has a direct interest in the purpose of a proposed undertaking.

The mathematical expression of the water balance.

The liquid waste from domestic, commercial and industrial establishments. City of Toronto Wet Weather Flow Management Guidelines November 2006 49

Initial capturing and removal of unwanted contaminants, such as debris, sediment, leaves and pollutants, from stormwater before reaching a best management practice; Examples include, settling forebays, vegetated filter strips and gravel diaphragms.

The technique of removing pollutants from runoff as it infiltrates through the soil.

A shallow excavated surface depression containing prepared filter media, mulch, and planted with selected vegetation.

A shallow constructed channel, often grass-lined, which is used as an alternative to curb and channel, or as a pretreatment to other measures. Swales are generally characterized by a broad top width to depth ratio and gentle grades.

That storm drainage system which is frequently used for collecting, transporting, and disposing of snowmelt, miscellaneous minor flows, and storm runoff up to the capacity of the system. The capacity should be equal to the maximum rate of runoff to be expected from the minor design storm which may have a frequency of occurrence of one in 2, or 5 years. The minor system may include many features ranging from curbs and gutters to storm sewer pipes and open drainage ways.

The slow movement of water into or through a soil or drainage system.

Penetration of water through the ground surface.

Layer of rock or soil that holds or transmits water.

(1) Something that pollutes, especially a waste material that contaminate air, soil, or water. (2) Any solute or cause of change in physical, chemical or biological properties that render water unfit for a given use.

The changing of land cover and land uses from rural to urban; the growth of urban settlements.

The upper surface of the zone of saturation, except where the surface is formed by an impermeable body.

Subsurface water level which is defined by the level below which all the spaces in the soil are filled with water; The entire region below the water table is called the saturated zone.

Open space floodway channels, road reserves, pavement expanses and other flow paths that convey flows typically in excess of the capacity of the Minor Drainage System.

A shallow constructed channel, often grass-lined, which is used as an alternative to curb and channel, or as a pretreatment to other measures. Swales are generally characterized by a broad top width to depth ratio and gentle grades.

Relating to the properties, distribution and effects of water on and below the earth’s surface, and in the atmosphere.

The liquid waste from domestic, commercial and industrial establishments. City of Toronto Wet Weather Flow Management Guidelines November 2006 49

The portion of water precipitated onto a catchment area, which then flows as surface discharge from the catchment area past a specified point.

Water from rain, snow melt, or irrigation that flows over the land surface.

The addition of water to ground water by natural or artificial processes.

The infiltration and movement of surface water into the soil, past the vegetation root zone, to the zone of saturation or water table.

Toronto and Region Conservation Authority

Layer of rock or soil that holds or transmits water.

A hard surface area (e.g., road, parking area or rooftop) that prevents or retards the infiltration of water into the soil.

The total surface area upstream of a point on a stream that drains toward that point. Not to be confused with watershed. The drainage area may include one or more watersheds.

The natural ground material characteristic of or existing by virtue of geographic origin.

The rate at which stormwater percolates into the subsoil measured in inches per hour.

Structures constructed of a non-erosive material, such as suitably sized aggregate, wood, gabions, riprap, or concrete; used to slow runoff water. Can be employed in practices such as bioswales and enhanced grass swales.

Linear bioretention cell designed to convey, treat and attenuate stormwater runoff. The engineered filter media soil mixture and vegetation slows the runoff water to allow sedimentation, filtration through the root zone, evapotranspiration, and infiltration into the underlying native soil.

The rate at which stormwater percolates into the subsoil measured in inches per hour.

A parameter that describes the capability of a medium to transmit water.

Low Impact Development. A stormwater management strategy that seeks to mitigate the impacts of increased urban runoff and stormwater pollution by managing it as close to its source as possible. It comprises a set of site design approaches and small scale stormwater management practices that promote the use of natural systems for infiltration and evapotranspiration, and rainwater harvesting.

Initial capturing and removal of unwanted contaminants, such as debris, sediment, leaves and pollutants, from stormwater before reaching a best management practice; Examples include, settling forebays, vegetated filter strips and gravel diaphragms.

Refers to the conditions in which an organism lives and survives or the conditions in which an organism resides. These conditions can be described as aspects of a “physical”, “social” or an “economic” environment, depending on the perspective perceived by the observer.