Groundwater Use in Nova Scotia
Groundwater is an important source of water for private wells, public water supplies, agricultural supplies, industrial supplies and commercial supplies throughout the province. Of the 82 municipal water supplies in Nova Scotia, approximately 34% obtain their water from groundwater sources and 12% use a combination of groundwater and surface water. In addition, groundwater supplies are used by most of the small registered public water systems in Nova Scotia, which provide water to facilities such as rural schools, day cares, nursing homes, restaurants and campgrounds.
Groundwater Occurrence in Nova Scotia
Groundwater is formed when rain or snowmelt seeps into the ground where it is stored in the pore spaces of soil or in the cracks or pores of rock. It is always moving underground, however, unlike surface water it moves very slowly. Typically, groundwater may travel between a few meters per year and 100's of metres per year. It usually flows toward surface water bodies, travelling downslope from highland areas to lowland areas. Eventually, groundwater is either pumped out of the ground by a water well or it discharges to a surface water body.
In Nova Scotia, groundwater is found in bedrock aquifers and in overburden aquifers (i.e. loose soil and rock located above the bedrock). An aquifer is a water-bearing formation that will yield water in a usable quantity to a well. The water table in Nova Scotia is usually found within about 5 m (15 feet) of ground surface, but can be deeper in areas with higher topography, such as the Cape Breton Highlands.
Bedrock aquifers generally consists of three main rock types:
- igneous and metamorphic rocks such as slate, quartzite and granite, which yield water mainly from fractures;
- sedimentary rocks such as sandstone, shale and conglomerate, which yield water from spaces between the grains and from fractures; and
- carbonate and evaporite rocks such as limestone and gypsum, which yield water mainly from fractures and cavities.
Figure 1 (below) shows where these rock types are located in Nova Scotia.
Figure 1: Groundwater Regions of Nova Scotia.
Bedrock aquifers are the most commonly used aquifers in Nova Scotia. Water is drawn from bedrock aquifers with drilled wells. Drilled wells are installed by boring a hole into the aquifer with a drill rig. The upper part of the borehole is lined with casing, usually made of steel with a minimum six inch diameter. The casing prevents the borehole walls from collapsing and, along with a drive shoe or grout seal, helps prevent contaminants from entering the well. Drilled wells in Nova Scotia are typically less than about 90 m (300 feet) depth, but may be deeper in some areas. How much water a drilled well yields depends on the type of bedrock, depth to groundwater, well depth, and the number of fractures (cracks) or permeable layers encountered during drilling.
In most places in Nova Scotia, the overburden aquifer above the bedrock is made up of glacial till, which consists of a mixture of clay, silt, sand, and rock. The thickness of the overburden aquifer varies widely with location, but generally ranges from 0 to 10 m (0 to 33 feet) and averages 6 m (20 feet). Dug wells are often used to obtain water from the overburden aquifer. A dug well consists of an excavation into the aquifer, usually made with a backhoe or excavator, that is lined with concrete crocks. The crocks prevent the collapse of the excavated walls and, along with an apron and seal, exclude surface contaminants from entering the well. Because till generally does not yield much water, dug wells are usually constructed of 90 cm (3 foot) diameter crocks that can store large amounts of water. Dug wells are usually less than 10 m (30 feet) deep.
In some places, the overburden aquifer consists of permeable sand and gravel deposits that are saturated with water. Here, dug wells or screened drilled wells may produce relatively good yields. Such deposits occur along some of the major river systems, the most extensive on the mainland being in the Annapolis and Musquodoboit Valleys.
Groundwater Quality in Nova Scotia
Naturally-occurring water quality problems in Nova Scotia include arsenic, chloride, hardness, iron, manganese, radionuclides, radon, sulphate and uranium. Most of these problems are related to the natural chemistry of the soil and rock where the well is located. Chloride problems may also come from seawater, and is a common problem in wells that are located close to the ocean. Visit our page on drinking water quality and treatment to find out more about these types of natural contaminants.
The main human-made water quality problems include bacteria and nitrate from septic fields and fertilizers; chlorides from road salt; hydrocarbons from leaking gas and oil tanks; solvents, such as perchlorethylene (used at drycleaners and other industrial facilities); methane, sulphates and chlorides from landfill sites; and pesticides.
Some of the common water quality problems that can occur in Nova Scotia, such as arsenic, pose a potential health hazard, while others are merely aesthetically displeasing (i.e., they may stain laundry or cause bad taste or odour). The most common parameters that exceed health-related drinking water guidelines include arsenic, bacteria, nitrate and uranium. The most common parameters exceeding aesthetic drinking water guidelines include chloride, hardness, iron and manganese.
Table 1 (below) provides information about common water quality problems and possible causes. Maps are available that show which areas are more likely to have arsenic and uranium problems, however, water quality can vary greatly from well to well, and the only way to know if your water is safe to drink is to test it regularly. See our page on private wells to find out more about water testing.
|Coliform bacteria||Health problems|
|Hardness||Hard scaly deposits in kettles and piping, bathtub ring, soap scum, high soap consumption|
|Iron||Red or orange stains on laundry or fixtures, metallic taste, rust particles after water sits|
|Manganese||Black stains on laundry or fixtures, metallic/bitter taste in coffee and tea|
|Iron bacteria||Red to brown slime in toilet tank, iron staining, unpleasant taste or odour|
|Low alkalinity||May cause corrosion of piping (green stains due to copper corrosion)|
|Hydrogen sulphide and/or sulphate-reducing bacteria||Rotten egg odour and flavour, silverware may turn black, worse in hot water|
|Turbidity||Cloudy, dirty or muddy appearance|
|Sodium||High blood pressure|
|Chloride||Salty taste, corrosive|
|Gasoline and/or oil||Oily smell or film on water|
|Nitrate||'Blue babies' in formula-fed infants under 6 months|