Nitrate Levels in the Abbotsford Aquifer an indicator of groundwater contamination in the Lower Fraser Valley

What is Happening?

Contamination of the ground waters of the Abbotsford Aquifer by nitrates has been observed by Environment Canada and others since the early 1950s (Liebscher et al., 1992). A monitoring program for the area of the Aquifer south of Abbotsford, B.C., was developed by Environment Canada in the early 1970s and a number of sites in this study area have been sampled regularly. Since 1992, the average concentrations of nitrate (expressed as nitrogen or nitrate-N in this indicator) observed at these sites have frequently exceeded the 10 mg/L Guideline for Canadian Drinking Water Quality. Of 2,757 ground water samples collected from monitoring wells called piezometers, 71% of these study area samples have exceeded the 10 mg/L nitrate as nitrogen Guideline with individual values ranging from a low of 0.03 mg/L to a high of 91.9 mg/L (see Graph below).

Source: Environment Canada, Pacific and Yukon Region, Vancouver, B.C. 2004. Note: Nitrogen values are measured as nitrate+nitrite (NO₃ + NO₂), however, greater than 99% of the nitrogen in ground water is usually nitrate (NO₃). From May 1992 to Dec. 1994, 19 piezometers were used for sampling. This was increased to 22 from February 1995 to March 1998, and from April 1998 onwards, 23 were used. Since 1996, monitoring has been conducted on a monthly basis. Prior to 1996, monitoring was every 2 to 4 months. Most sites were intentionally chosen in areas of intense agricultural activities or down gradient from them. For details on piezometers and sampling depths consult Table.

GRAPH DATA

The large range in maximum and minimum nitrate concentrations reflects the different conditions observed at different piezometers. Nitrate concentrations in some piezometers fluctuated above and below the nitrate Guideline, while in others they were consistently below or above the Guideline. The maximum nitrate concentrations measured in 1996, 1997 and 1998 were from samples taken from one piezometer. Nitrate concentrations can be very site specific and  dependent on the local soil characteristics, topography and the land use activities near and up-gradient from the sampling site. Precipitation recharges or adds water to the aquifer, and the leaching of nitrogen compounds from the soil to the ground water as water percolates downward has an effect on nitrate values.

The study area includes the central, more agriculturally developed part of the aquifer and many of the sampling sites tend to be located near the international border. Consequently, some researchers do not consider these study area nitrate concentration data as being representative of the entire aquifer. A recent federal/provincial report on trends in water quality in B.C. reports that of ninteen monitoring wells sampled in the Abbotsford Aquifer, nine exceeded the nitrate drinking water guideline (Water Quality Trends in Selected British Columbia Waterbodies, March 2000). Other studies by Liebscher et al., 1992; Carmichael et al., 1995; Wassenaar, 1995; Zebarth et al., 1998 and Hii et al., 1999 have all shown elevated nitrate concentrations over a wide portion of the aquifer.

Why is it Happening?

The Abbotsford Aquifer is located in an extensive sand and gravel deposit and covers an area of approximately 100 km² in B.C. and a similar area in Washington State, USA.

The Aquifer is largely unconfined (not protected from land surface drainage by an impermeable clay layer) and, thus is highly vulnerable to contamination from land use practices.

The land area over the Abbotsford Aquifer in B.C. is undergoing large land use changes due to population growth and the accompanying industrial, commercial and agricultural development. This activity is producing multiple potential sources of nitrate contaminants from manure and chemical fertilizers, septic effluent discharges and airport de-icing urea. However, recent studies (Zebarth et al., 1998; Waasenaar, 1995) have shown that the elevated nitrate concentrations in the aquifer are primarily from agricultural sources such as animal manure.

Agriculture and Agri-Foods Canada reviewed agricultural census information for 1971, 1981 and 1991 and estimated that nitrogen additions from the various agricultural sources in the area of the Abbotsford Aquifer exceeded nitrogen use by crops by as much as 50%. This surplus nitrogen creates a high potential for nitrate leaching to ground water.  A 100 kg nitrate-N surplus per cropped ha in the soil root zone would have the potential to result in ground water with nitrate-N greater than 10 mg/L (Zebarth et al., 1998).

The increase in surplus nitrogen from 1971 to 1991 shown for the Abbotsford area is primarily due to a shift in farming activity. There have been major changes in animal and crop production with a resulting decrease by almost 20% in cropped land area (Zebarth et al., 1998). 

Animal production has shifted from dairy/beef production, which utilizes a local land base for crop production and grazing, to poultry production (especially for meat) which relies mainly on imported feed.

The type of crops grown has also changed from grass hay and pasture to small fruit (mainly raspberry) production. Small fruit crops have increased substantially from 16% of the cropped land in 1971 to 54% in 1991. Unlike grass hay and pasture, small fruit crops require much less nitrogen for crop production.

Manure from poultry operations has traditionally been applied to nearby raspberry fields as well as to other crops. A 1990 survey of the raspberry farms of the Fraser Valley conducted by the Sustainable Poultry Farming Group also reported an average application of 38 kg/ha of commercial inorganic nitrogen fertilizer. Raspberry production accounts for approximately 17 sq. km. of the agricultural land use over the entire aquifer area in B.C. and 80% of this raspberry production occurs within the approximately 25 sq. km. study area (Hii et al., 1999).

The increased poultry production, decline in dairy production and shift to crops which require much less nitrogen are responsible for the concentration of nitrogen within a relatively small geographical area. As a result, the local agricultural land base is unable to use the nitrogen surplus.

Why is it Significant?

The Abbotsford Aquifer is one of approximately 200 in the Lower Fraser Valley. It is the largest unconfined aquifer and the most extensively used in the Valley. It is a transboundary aquifer which currently provides ground water to over 100,000 people in the City of Abbotsford and in north central Whatcom County of Washington State, USA. It is an important source of water for domestic, municipal, agricultural and industrial uses on both sides of the border. The direction of ground water flow in the Canadian portion of the aquifer is generally southward to the USA. There has been concern raised by some counties in Washington State whose capture zones for their drinking water well fields extend into areas with high ground water nitrate levels on the Canadian side.

In terms of human health, toxicity of nitrate is thought to be due to its reduction to nitrite during digestion.  Nitrites can affect human health by reducing the ability of blood to carry oxygen.  Infants are particularly at risk from drinking water with high nitrate concentrations (i.e., 10 mg of nitrate-nitrogen per liter or more in drinking water ). For infants, a potentially fatal condition called "methaemoglobinaemia' or "blue baby syndrome" may result. There was one suspected case of this syndrome reported in the mid-70's in the Lower Fraser Valley (Dr. Guasparini, South Fraser Health Region, pers. comm., May 1999). There is also some concern from the human health standpoint of an increased risk of cancer from high nitrate levels in drinking water (for more details on nitrate effects on human health consult Health Canada's nitrate/nitrite guidelines. Note that Health Canada expresses the nitrate Guideline as 45 mg/L of nitrate, i.e., the whole nitrate molecule of NO₃ and this is equivalent to 10 mg/L of nitrate expressed as nitrogen, i.e., the nitrogen element of the nitrate molecule).

Nitrate is also a major nutrient for aquatic vegetation. For ground water fed streams and rivers, excessive amounts of nitrate and other nutrients in ground water can lead to prolific growth of algae, fungi and aquatic rooted, attached and floating plants. This can render waterways unsuitable for some other uses.

What is Being Done?

The federal government strongly supports the recent adoption by governments of the source to tap, multi-barrier approach to protecting drinking water for Canadians. The multi-barrier approach highlights the importance of protecting the lakes, rivers and aquifers which are the sources of drinking water, as well as ensuring effective treatment and distribution systems. The federal government is committed to enhancing its research to identify, understand and reduce the human and environmental impacts of micro-biological and chemical substances which contaminate water sources and aquatic ecosystems. The government is also working with all provinces and territories to ensure understanding and knowledge of threats to water quality are shared, and strategies to reduce or eliminate impacts can be put in place by individual jurisdictions. In addition, all governments are collaborating on accelerating drinking and source water quality guidelines development, linking monitoring networks to better share information on water quality issues and trends, and providing Canadians with information on the quality of their water.

The Abbotsford Aquifer is a transboundary aquifer whose water quality is threatened from land use activities on both sides of the Canada-USA border. Environment Canada (EC) conducts research on the aquifer's water quality and quantity including monitoring, mapping and modeling. Results are published by Environment Canada and made available as part of an ongoing collaboration with other government agencies and the private sector to improve management of the aquifer and protect ground water.

Under the Fraser River Action Plan (FRAP), financial support was  provided to assist the Sustainable Poultry Farming Group (SPFG) in its program to remove some of the excess manure to markets away from the aquifer. Working with other federal and provincial agencies, Environment Canada's FRAP also undertook several studies on ground water of the Lower Fraser Valley. These included identification of sources of aquifer contamination and agricultural nutrient management studies. FRAP supported the development of Environmental Guidelines for various agricultural commodity groups and studies on farm practices in areas other than the Abbotsford Aquifer.

Since 1996, EC has initiated new projects on ground water characterization and intensified the Abbotsford Aquifer monitoring effort by increasing sampling to consistent monthly intervals for 23 selected piezometers. This was increased to 24 in 1998. It also initiated and implemented, in partnership with other federal and provincial agencies, projects to educate the public on ground water stewardship. These include the production of a newsletter called Groundwater Keeper, a septic maintenance video and a ground water protection video. These activities, together with support for SPFG, continue to be funded under Environment Canada's Georgia Basin Action Plan.

Environment Canada with the BC Ministry of Water, Land and Air Protection and BC Ministry of Agriculture and Food have also recently entered into an agreement with the Fraser Basin Council to consult with Lower Fraser Valley agriculture stakeholders about manure management.

In 1992, British Columbia adopted an agricultural waste control regulation and associated code of practice under the provincial Waste Management Act. The code describes practices for using, storing and managing agricultural wastes in an environmentally sound manner. In 1995, the community of Abbotsford formed an aquifer stakeholder group to work on developing "home-grown" voluntary-type initiatives. Nearly 40 representatives from agriculture, the rural residential community, business and industry, provincial and federal government agencies, ENGOs, the City of Sumas Washington, and other interested parties have been promoting, supporting, facilitating and in some cases coordinating various initiatives. In 1998, the Ministries of Environment, Lands and Parks and Agriculture and Food and the BC Agriculture Council formed the Partnership Committee on Agriculture and the Environment. Its role is to establish a single-window approach for consultation on environmental issues that affect farmers and agriculture. Environment Canada is a member of this Committee. For more general information on provincial activities on ground water consult the BC Ministry of Water, Land and Air Protection'  indicator on groundwater and groundwater web site.

For more information contact: Basil Hii of Environment Canada for groundwater issues or Laurens van Vliet of Agriculture and Agri-Foods Canada for agricultural issues.

Check the following sites for additional information on this indicator:

• Environment Canada's general information series on Groundwater.
• Environment Canada's Groundwater quality site
• Canadian Environmental Quality Guidelines
• Health Canada - Guidelines for Canadian Drinking Water Quality - Nitrate/nitrite
• Environment Canada - Threats to Sources of Drinking Water and Aquatic Ecosystem Health in Canada

The following Web sites are not under the control of Environment Canada (EC) and they are provided solely for the convenience of users. Environment Canada is not responsible for the accuracy, currency or the reliability of the content. Environment Canada does not offer any guarantee in that regard and is not responsible for the information found through these links, nor does it endorse the sites and their content. Users should be aware that information offered by non Government of Canada sites that are not subject to the Official Languages Act, and to which Environment Canada links, may be available only in the language(s) used by the sites in question.

• Groundwater in British Columbia, detailed information on BC's groundwater
• BC Ministry of Water, Land & Air Protection environmental indicator series Groundwater in British Columbia,
• BC Ministry of Water, Land & Air Protection  Well Protection ToolKit
• A Canadian Groundwater Strategy - draft report on groundwater management approach
• US EPA Office of Ground Water and Drinking Water
• Ground Water in Washington State

For references used in this indicator click here.