Glossary, A – D

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Abandoned Well

A well that is deserted because it is dry, contains unpotable water, discontinued before completion, not being properly maintained, constructed poorly, or determined that natural gas may pose a hazard.


One or a series of related processes, natural or anthropogenic that occur within a geographical area and may be related to a particular land use.

Aggregate Risks

Multiple risks in a municipal water supply protection area that are considered together relative to the overall risk to drinking water sources.

Ambient water

Natural concentration of water quality constituents prior to mixing of either point or non-point source load of contaminants.


An underground saturated permeable geological formation that is capable of transmitting water in sufficient quantities under ordinary hydraulic gradients to serve as a source of groundwater supply.

Aquifer Vulnerability Index (AVI)

A numerical indicator of an aquifer’s intrinsic or inherent vulnerability susceptibility, to contamination expressed as a function of the thickness and permeability of overlying layers.

Bankfull stage

Stage at which a stream first overflows its natural banks.


Bogs are peat-covered areas or peat-filled depressions with a high water table and a surface carpet of mosses, chiefly Sphagnum. The water table is at or near the surface in the spring, and slightly below during the remainder of the year. The mosses often form raised hummocks, separated by low, wet interstices. The bog surface is often raised, or, if flat or level with the surrounding wetlands, it is virtually isolated from mineral soil waters. Hence, the surface bog waters and peat are strongly acid and upper peat layers are extremely deficient in mineral nutrients.

Broader Landscape

The watershed or Source Water Protection Study area. Applies to regional rather than local aquifer vulnerability assessments usually using an indices method of vulnerability assessment.


A substance used in conjunction with, or associated with, a land use activity or a particular entity, and with the potential to adversely affect water quality.

Conceptual Water Budget

A written description of the overall flow system dynamics for each watershed in the Source Protection Area taking into consideration surface water and groundwater features, land cover (e.g. proportion of urban vs. rural uses), human-made structures (e.g. dams, channel diversions, water crossings), and water takings.

Confined Aquifers

An aquifer that is bounded above and perhaps below by layers of geological material that do not transmit water readily.

Consumptive Water Demand

The net amount of water that is taken from a source, and not returned locally to the same source in a reasonable time.


Chemicals and pathogens.

Contaminant of Concern

A chemical or pathogen that is or may be discharged from a drinking water threat.

Cumulative (water quality) Effects

The consequence of multiple threats sources, in space and time, which affect the quality of drinking water sources.

Cumulative (water quantity) Effects

The consequence of multiple threats sources, in space and time, which affect the quantity of drinking water sources.

Dense Non-Aqueous Phase Liquids (DNAPL)

A dense non-aqueous phase liquid that is both denser than water and is immiscible in or does not dissolve in water.

The term DNAPL is used  to describe contaminants in groundwater, surface water and sediments. DNAPLs tends to sink below the water table when spilled in significant quantities and only stop when they reach impermeable bedrock. Their penetration into an aquifer makes them difficult to locate and remediate.

Data Gaps

The lack of raw information for a specific geological area and/or specific type of information.

Decommissioned Wells

Capped, plugged and sealed in compliance with regulatory requirements by the Ministry of the Environment.

Designated System

A drinking water system that is included in a terms of reference, pursuant to resolution passed by a municipal council under subsection 8(3) of the Clean Water Act, 2005.

Developed / Developable

Reference to the usable portion of a parcel of land that meets the regulatory zoning provisions, particularly those pertaining to defining the area of occupation for buildings, structures, facilities and infrastructure.

Drinking Water Concern

A purported drinking water issue that has not been substantiated by monitoring, or other verification methods; will be identified through consultations with the public, stakeholder groups, and technical experts (e.g. water treatment plant operators).

Drinking Water Issue

A substantiated (through scientific means) condition relating to the quality of water that interferes or is anticipated to soon interfere with the use of a drinking water source by a municipal residential system or designated system.

Drinking Water Threat

An existing activity, possible future activity or existing condition that results from a past activity, (a) that adversely affects or has the potential to adversely affect the quality or quantity of any water that is or may be used as a source of drinking water, or (b) that results in or has the potential to result in the raw water supply of an existing or planned drinking-water system failing to meet any standards prescribed by the regulations respecting the quality or quantity of water, and includes an activity or condition that is prescribed by the regulations as a drinking water threat.

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