The Coliforms Indicator (official name: Indicator of the Risk of Water Contamination by Coliforms) evaluates the relative risk of surface water contamination by pathogens from manure such as viruses, bacteria and protozoa, across agricultural areas in Canada. This indicator has tracked coliform risk associated with Canadian agricultural activities from 1981 to 2016.
Overall state and trend
Coliform risk has been fairly stable on agricultural lands in Canada, with the majority of agricultural land considered to be at low or very low risk. From 1981 to 2016, the level of risk has essentially remained unchanged, though the risk has shifted from regions where livestock production has decreased to regions where it has intensified.
Use the interactive map below to zoom in and explore different regions. Note that in the Central Prairies, risk is considered to be very low, while southwestern Alberta and the British Columbia interior have regions of high to very high risk. Small pockets of high or very high risk are found in other livestock regions of the country as well.
|Very Low||Low||Moderate||High||Very High|
Use the interactive map in Figure 2 to explore the change in coliform risk between 1981 and 2016. Risk is determined by both source (livestock pasturing or manure spreading) and transport (runoff from snowmelt or rainfall). Generally speaking, increases in risk observed between 1981 and 2016 were caused by an intensification of livestock production in parts of Alberta and southern Manitoba. Decreases were caused by a shift from livestock (notably cattle and swine) to annual crop production in Ontario, Quebec and the Maritimes, which has lowered the risk of coliform contamination.
|Large decrease||Decrease||Little or no change||Increase||Large increase|
Risk of Water Contamination by Coliforms performance index
The state and trend of the Coliforms Indicator can also be seen in the performance index below.
Description - Figure 3
In 2016, the state of the environment rating, as it relates to coliforms risk resulting from farming activities in Canada, had returned just into the “Desired” category, after a period of about 20 years in the “Good” category.
What is reflected here is that, though total coliform loads have increased with growing livestock numbers over time, which decreases this rating, the coliform risks have also been concentrated into smaller regions, which improves this rating. The index combines the total risk with the degree to which the risk is concentrated into specific areas.
- Trend 1 – Livestock numbers declining nationally, but intensification of production leads to increasing risk
- Trend 2 – Wet weather increases risk of contamination
This section highlights a few other trends of interest. In some cases, these are occurring in certain regions and in others they are affecting certain sectors, such as the beef or dairy industries. This is not an exhaustive list; additional findings can be found in the full publication: Environmental Sustainability of Canadian Agriculture, Agri-Environmental Indicator Report Series - Report #4
Trend 1 – Risk varies with both livestock numbers and the intensification of production
In Canada, livestock production has been concentrated onto fewer farms, though the total livestock production has increased over time. Both cattle and pig production decreased significantly between 2006 and 2011, and poultry production plateaued during that time. Poultry and pig production have been increasing again since 2009, but cattle production has continued to decline. These animals are now concentrated onto one-third the number of farms as in 1981. (Figure 4).
(Note that lines represent animal populations and bars represent number of livestock farms.)
Description - Figure 4
|Cattle (beef and dairy)||12,765,000||11,372,000||12,066,000||14,227,000||14,516,350||15,327,000||12,850,000||12,070,000|
|Poultry (chickens and turkeys) × 10||10,142,250||9,564,075||10,294,968||11,084,134||13,260,947||13,145,295||13,380,652||14,538,024|
|Number of farms reporting||327,535||248,883||218,000||191,502||164,022||144,110||113,906||107,619|
Consequences of intensifying animal production
In addition to a tendency for higher animal densities in pastures, another potential consequence of intensification is that on-farm manure volumes may grow to exceed the capacity of the surrounding land to receive it, resulting in manure being applied at higher rates on the same or a smaller land base. This concentrates higher risk into smaller regions.
Trend 2 – Risk of contamination varies with weather conditions and timing of rainfall events
Weather conditions have a significant impact on the risk of water contamination by coliforms in any particular year. Colder weather reduces the number of coliforms in the soil. The risk to water is strongly dependent on the intensity of rainfall events, and their timing relative to manure spreading events. This weather-induced variability was largely removed from the model by using climate data normalized over 1981 to 2016. Figure 5 shows the impact on annual risk if we use annual weather data in the model instead of climate normals. Both soil coliform loads and risk to water vary dramatically year by year depending on what the weather is like.
Description - Figure 5
|Year||Load-Weather||Load-Climate Normal||Risk-Weather||Risk-Climate Normal|
Timing of runoff is also a major factor for coliform risk. In the western provinces, some animals remain outside during winter, keeping the amount of coliforms available for transport at its highest throughout the year (Figure 6).
Description - Figure 6
(British Columbia, Alberta, Saskatchewan, Manitoba) pasture
(Ontario, Quebec, New Brunswick, Nova Scotia, Prince Edward Island, Newfoundland and Labrador) pasture
|January||3.161 CFU × 1010||2.442 CFU × 1010|
|February||2.633 CFU × 1010||2.025 CFU × 1010|
|March||2.063 CFU × 1010||1.655 CFU × 1010|
|April||3.366 CFU × 1010||3.181 CFU × 1010|
|May||2.960 CFU × 1010||2.830 CFU × 1010|
|June||3.197 CFU × 1010||3.076 CFU × 1010|
|July||2.903 CFU × 1010||2.796 CFU × 1010|
|August||2.943 CFU × 1010||2.823 CFU × 1010|
|September||3.669 CFU × 1010||3.404 CFU × 1010|
|October||5.238 CFU × 1010||4.829 CFU × 1010|
|November||7.966 CFU × 1010||7.166 CFU × 1010|
|December||5.292 CFU × 1010||4.418 CFU × 1010|
In Eastern Canada, the risk is more variable across the seasons. Most animals are confined during winter months and the manure is stored for spreading during the warmer season. Across Canada, manure is spread at four times throughout the season: before planting, after planting but before emergence, after forage harvest, and after grain harvest (Figure 7). The timing between the period of spreading and the weather conditions during or following these periods has a critical impact on the risk value.
Description - Figure 7
(British Columbia, Alberta, Saskatchewan, Manitoba) cropland
(Ontario, Quebec, New Brunswick, Nova Scotia, Prince Edward Island, Newfoundland and Labrador) cropland
|January||0.0017 CFU × 1010||0.0064 CFU × 1010|
|February||0.0018 CFU × 1010||0.0016 CFU × 1010|
|March||0.0316 CFU × 1010||0.0706 CFU × 1010|
|April||0.1199 CFU × 1010||0.1168 CFU × 1010|
|May||0.5311 CFU × 1010||0.9018 CFU x 1010|
|June||0.0515 CFU × 1010||0.0514 CFU × 1010|
|July||0.0000 CFU × 1010||0.0000 CFU × 1010|
|August||0.0000 CFU × 1010||0.0000 CFU × 1010|
|September||0.1680 CFU × 1010||0.3576 CFU × 1010|
|October||0.2269 CFU × 1010||0.1760 CFU × 1010|
|November||0.8371 CFU × 1010||1.1803 CFU × 1010|
|December||0.0537 CFU × 1010||0.4455 CFU × 1010|
Why this indicator matters
Manure is a natural and valuable by-product of animal production, and can be used as a fertilizer to aid crop growth. However, animal manure may pose some risks to environmental and human health if bacteria from the manure end up in nearby surface water. The risk of contamination by coliforms is highest in areas with high manure production, dense water drainage networks and high susceptibility to surface runoff and soil erosion. Agriculture has the potential to mitigate risk from coliforms by implementing beneficial management practices (BMPs) that prevent or minimize livestock access to water or that reduce manure application rates or that prevent runoff contaminated with manure from reaching water bodies.
Beneficial management practices
Strategies for reducing the risk of water contamination by coliforms include reducing the risk of transport to surface water, decreasing the amount of manure used and managing livestock near surface water bodies.
At the national scale, manure from pastured animals was the largest source of coliforms potentially available for transport to surface water. Adding fencing along surface water bodies to prevent access by pastured animals, as well as discouraging access to streams by providing off-site watering facilities, will reduce this risk. Reducing livestock density on pastureland could also be considered where feasible.
For manure spreading, any practice that incorporates manure into the soil immediately or shortly after application will substantially reduce the risk of coliform transport to streams. Strict nutrient management will help ensure that the minimum amount of manure necessary (that is, the amount that can be used by the growing crop) is spread onto the receiving fields. Because surface runoff is an important coliform transport mechanism, it is critical that manure be spread in suitable weather conditions with the recommended application techniques. BMPs that reduce runoff or soil erosion or increase soil organic matter content help reduce coliform transport. Risk can be managed by establishing suitable spreading setback distances from water bodies or streams, and by establishing buffer strips around water bodies.
Farmers can also explore other strategies, such as reducing the amount of manure per animal through targeted feeding strategies. Retention ponds can be constructed directly downstream from feedlots or manure storage areas to capture and neutralize coliforms (through the effect of ultraviolet light from sunlight) before the water is used on-farm as irrigation water. Artificial wetland areas on farms can also perform this function. In cases where manure must be stored prior to spreading, storage facilities should be designed and maintained so as to prevent overflow and leakage. Lastly, where manure spreading is not an economically viable option (for example where manure production exceeds local demand and hauling costs are high for longer-distance transportation), farmers can explore options for advanced manure management techniques such as biogas digesters and slurry fractionation that stabilize manures and capture nutrients.
About the performance indices
The agri-environmental performance index shows environmental performance state and trends over time, based on weighting the percentage of agricultural land in each indicator class, such that the index ranges from 0 (all land in the most undesirable category) to 100 (all land in the most desirable category). An index value that is increasing over time suggests improving environmental performance, while a decreasing index value suggests deteriorating environmental performance over time.
- The Nitrogen Indicator tracks the risk of water contamination from nitrogen.
- The Phosphorus Indicator examines risk to water from phosphorus.
- The Pesticide Indicator examines risk to water from pesticides.
Additional resources and downloads
- For detailed information on this indicator please see the publication entitled Environmental Sustainability of Canadian Agriculture, Agri-Environmental Indicator Report Series - Report #4.
- Discover and download geospatial data related to this and other indicators.