Government of Nova Scotia
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Environment

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Groundwater

Groundwater Management

In order to manage and protect groundwater, it is necessary to: evaluate the quality and quantity of groundwater that is available in the province's aquifers; allocate the available groundwater amongst the various users; protect the quality of groundwater by minimizing contamination from human activities; and, monitor groundwater to track long-term trends in its quality and quantity and to assess the effectiveness of our groundwater management programs.

Some of the department's key groundwater management initiatives used to meet these objectives include (details below):

The department also manages and reports on the status of groundwater by developing and maintaining publications, databases and maps.

Groundwater Resource Evaluation

The goal of groundwater resource evaluation is to provide an inventory of groundwater resources. This includes assessing both the quality and quantity of groundwater in the province's aquifers. The information gathered during groundwater resource evaluations is used to answer questions such as "How much groundwater is available?" and "What is the quality of the groundwater?". Groundwater resource evaluation is a key step in groundwater management because groundwater resources are not unlimited and, therefore, knowing how much groundwater is available helps to prevent over-exploitation and promotes sustainable development.

Groundwater resource evaluation studies began in Nova Scotia in the 1960's and reports have been completed for approximately half of the province. View the list of available groundwater resource reports and maps.

Recently, the Earth Science Sector of Natural Resources Canada (NRCan), in partnership with Nova Scotia Environment and Labour, has carried out groundwater resource evaluations in two areas of Nova Scotia: Cumberland County and the Annapolis Cornwallis Valley. The first project, which was called the Maritimes Groundwater Initiative (MGWI) project, covered areas in Cumberland County, NS, as well as areas in New Brunswick and PEI. The MGWI reports are available for download at the NRCan publications page. The second project, which is called the Annapolis Cornwallis Valley Aquifer Study (ACVAS), is currently in progress. View the preliminary results from the ACVAS project.

Sustainable Groundwater Development

The goal of sustainable groundwater development is to ensure that groundwater use does not exceed the sustainable yield of the province's aquifers. The sustainable yield of an aquifer is defined as the total groundwater withdrawals that can be maintained indefinitely without causing unacceptable environmental, economic or social consequences. The sustainable aquifer yield is assumed to be no greater than 50% of the annual aquifer recharge, unless it can be demonstrated that additional withdrawals will not cause unacceptable effects. The 50% unallocated portion is retained to maintain base flow for surface water bodies.

Sustainable groundwater development is promoted in the province by requiring groundwater withdrawal approvals if a groundwater withdrawal exceeds 23,000 litres per day (5,000 gallons per day), and through the Water Resources Protection Act which controls large scale removals of water from the province.

Groundwater withdrawal approvals allow the department to assess the potential effects of each proposed groundwater withdrawal on a case-by-case basis and track how much groundwater has been allocated in the province. For each groundwater withdrawal approval application, a hydrogeological study must be completed to evaluate the potential effects of the proposed withdrawal on existing groundwater users and the environment. The evaluation includes an assessment of the following: sustainable yield of the aquifer, well interference effects, water quality effects, the potential for sea water intrusion and groundwater-surface water interaction.

The department uses the following guiding principles to allocate groundwater withdrawals:

  1. Withdrawals from the aquifer must be sustainable (i.e., can be maintained indefinitely without causing unacceptable environmental, economic or social consequences);
  2. New groundwater withdrawals should not cause any significant adverse effects to existing groundwater users or the environment;
  3. Groundwater allocations are based on a "first-come, first-served basis" with priority given to drinking water applications; and
  4. Groundwater allocations are based on the applicant's current water needs and the applicant cannot typically reserve water for future use beyond the expiry date of the approval (i.e., 10 years).

Visit our page on water withdrawal approvals for information on how to apply for a groundwater withdrawal approval.

Groundwater Protection

The goal of groundwater protection is to protect the quality of groundwater by minimizing contamination from human activities. Groundwater quantity is also protected, however, these initiatives are described above in the "Sustainable Groundwater Development" section. The department promotes the protection of groundwater quality in several ways, including: requiring wells to be properly constructed; requiring old abandoned wells to be properly sealed so they cannot act as pathways for contamination; and, by requiring approvals for activities or facilities that have the potential to contaminate groundwater, such as septic systems and landfills.

The department is also working with municipalities and stakeholders to protect municipal drinking water supplies, including both surface water and groundwater supplies. The five step process used to develop a source water protection plan in Nova Scotia is similar for groundwater and surface water supplies. The main difference occurs during Step 2 (PDF: 2.2mb) of the process, which involves delineating the wellhead protection area.

Wellhead Protection Areas in Nova Scotia

To protect a groundwater supply, you must delineate the area that contributes water to the well so that potential sources of contamination can be identified and managed. The source water protection area surrounding the well or well field is called the Wellhead Protection Area (WHPA).

The Wellhead Protection Area (WHPA) includes all or part of the of the area that contributes groundwater to the well field and is typically divided into several smaller zones that are used to manage different types of contaminants. The different zones in the WHPA are based on the time it takes groundwater to travel to the well. Zones that are closer to the well require a higher level of protection because there is a shorter distance to travel before groundwater reaches the well. In Nova Scotia, a minimum of three WHPA zones are recommended, as follows:

  • Zone 1 - (0 to 2 year travel time). This zone is used to protect against microbial contaminants (e.g., bacteria and viruses) and all chemical contaminants.
  • Zone 2 - (2 to 5 year travel time). This zone is used to protect against all chemical contaminants, including persistent chemical contaminants (e.g., chlorinated solvents, nitrates, road salt, etc.) and non-persistent chemical contaminants (e.g., petroleum hydrocarbons).
  • Zone 3 - (5 to 25 year travel time). This zone is used to protect against persistent chemical contaminants (e.g., chlorinated solvents, nitrates, road salt, etc.).

In addition to the zones defined above, it is also recommended that a "well site control zone" be established to protect the area immediately surrounding the well. This area, which is considered to be the wellhead itself, is used to protect against the day-to-day activities of the water utility and any other potential sources of contamination, including vandalism. The well site control zone can be determined based on a simple fixed radius, which should be a minimum of 30 m.

For wells that have been classified as Groundwater Under the Direct Influence of surface water (PDF: 141k) (GUDI), there is potential for contaminants within the watershed to be rapidly carried to the well field by surface water, even if the contaminant sources are outside the 2-, 5-, or 25-year groundwater travel times. Therefore, for GUDI wells, the land area within the watershed boundaries should also be included within the WHPA. This approach ensures that the potential risk of contaminants migrating in surface water adjacent to a well field will be considered in the source water protection plan. Because groundwater outside the watershed may also contribute water to the well field, the WHPA zones should still be delineated for GUDI wells.

Methods to Delineate the Wellhead Protection Area

There are several methods available to delineate the WHPA. The preferred method in Nova Scotia is numerical modelling using a computer model. When properly set up and calibrated with adequate field data, computed models provide the best method to accurately delineate the WHPA.

Groundwater Monitoring

The department's groundwater monitoring programs are used to track long-term trends in groundwater quality and quantity and to assess the effectiveness of groundwater management programs. Monitoring programs are an essential tool for checking on the status of the province's groundwater, assessing the impact of human activities on groundwater, and evaluating long-term groundwater trends associated with issues such as climate change.

Two of the department's key groundwater monitoring programs are: the Nova Scotia Groundwater Observation Well Network, which tracks groundwater levels and groundwater chemistry through a network of wells across the province; and, the Well Water Nitrate Monitoring Program, which monitors nitrate levels in approximately 150 private wells in Kings County.