Coliforms Indicator

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 2011.

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 2011, the level of risk has increased slightly, primarily attributed to an intensification of animal production in some regions, whereby more animals are being raised in the same or less land area than in previous years.

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, with pockets of moderate to high risk in parts of western Alberta and southern Manitoba. The areas with the highest risk are in the Mixedwood Plains region of southern Ontario and Quebec, as well as parts of the Appalachian region of Quebec.

In addition to exploring the 2011 values, click the play button to view changes over time. From 1981 to 2011, there has been a very steady increase in risk across the Prairies, most significantly in parts of Alberta and southern Manitoba. With the exception of some parts of the Appalachian region of Quebec and parts of southern Ontario, Eastern Canada has seen a stable or improving trend.

Generally speaking, the increases in risk observed between 1981 and 2011 were caused by an intensification of livestock production in parts of Alberta and southern Manitoba, despite a decrease in production at a national level. In Eastern Canada and the Maritimes, the shift from livestock (notably cattle and swine) to annual crop production has lowered the risk of coliform contamination. It is important to note that 2011 was an extremely wet year in terms of snowmelt and rainfall on the Prairies and for rainfall in the Maritimes, which significantly increased runoff volumes and consequently transportation of coliforms to surface waters. Coliform risk would have been lower in all regions in a drier or average year.

Figure 1: Risk of water contamination by coliforms in agricultural watersheds under 2011 management practices

Legend: legend

Use the interactive map in Figure 2 to explore the change in coliform risk between 1981 and 2011. Risk is determined by both source (livestock pasturing or manure spreading) and transport (runoff from snowmelt or rainfall). It is apparent that the increase in risk is occurring across most of the Prairie Region.

Figure 2: Change in coliform risk between 1981 and 2011

Legend: legend

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.

Figure 3: Agricultural Ammonia Emissions performance index
Description of this image follows.
Description - Figure 3
Year Index Value
1981 91
1986 83
1991 84
1996 78
2001 89
2006 78
2011 82

In 2011, the state of the environment, as it relates to coliforms risk resulting from farming activities in Canada, was in the "Desired" category. The index illustrates a subtle downward trend, representing increased risk to water quality. The index levels improved from 2006 but are still below the 1981 baseline. It is important to note that risk is driven by runoff and is therefore much higher in wetter years.

The index tends to aggregate and generalize trends and so should be viewed as a policy tool to give a general overview of state and trend over time.

How performance indices are calculated

Specific trends

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 – Livestock numbers declining nationally, but intensification of production leads to increasing risk

In Canada, there has been a notable intensification of dairy, beef, swine and poultry production and concentration of these operations on fewer but larger farms (Figure 4). This trend of concentrating livestock on a smaller land base has continued between 2006 and 2011 despite the significant decreases in swine and cattle numbers at the national level. There has also been an increase in larger confined animal production facilities such as cattle feedlots, hog barns and poultry production facilities. The number of broiler and layer chickens has increased, while the number of farms raising these animals has decreased. Similarly, the average number of pigs per farm increased by 31.5% between 2006 and 2011 (Statistics Canada, 2013) and the number of dairy cows per farm has risen by about 13% since 2005 (Canadian Dairy Commission, 2012).

Figure 4: Concentration of livestock production in Canada from 1981 to 2011.
(Note that lines represent animal populations and bars represent number of livestock farms.)
Description of this image follows.
Description - Figure 4
1981 1986 1991 1996 2001 2006 2011
Cattle (beef and dairy) 13,501,904 11,997,608 12,972,038 14,893,034 15,551,449 15,773,527 12,789,965
Pigs 9,875,065 9,756,569 10,216,083 11,040,462 13,958,772 15,043,132 12,679,104
Poultry (chickens and turkeys) × 10 10,142,250 9,564,075 10,294,968 11,084,134 13,427,547 13,300,618 14,104,665
Number of farms reporting 327,535 248,883 218,000 191,502 164,022 144,110 113,906

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.

Trend 2 – Wet weather increases risk of contamination

The figures below show the importance that wet weather can have on this indicator. While the source of coliforms has increased in some areas (for example on pastures and as a result of spreading in the western Prairies), the second main factor affecting the risk of contamination is transportation—that is, how coliforms can be moved from the land to surface water. The primary means of transportation is water, through snowmelt runoff or rainfall, particularly storm events. Figure 5 shows the flows in the Assiniboine River at Headingley, Manitoba, illustrating the unusually wet conditions in the spring and summer of 2011.

Figure 5: Comparison of flow rates at the Headingley, Manitoba gauge station on the Assiniboine River in 2001 and 2011 (Environment Canada Water Office, 2015)
Description of this image follows.
Description - Figure 5
Average daily discharge in cubic metres by month, 2001
January 41 cubic metres
February 40 cubic metres
March 30 cubic metres
April 131 cubic metres
May 287 cubic metres
June 112 cubic metres
July 90 cubic metres
August 44 cubic metres
September 26 cubic metres
October 22 cubic metres
November 24 cubic metres
December 55 cubic metres
Average daily discharge in cubic metres by month, 2011
January 87 cubic metres
February 78 cubic metres
March 64 cubic metres
April 210 cubic metres
May 507 cubic metres
June 512 cubic metres
July 470 cubic metres
August 349 cubic metres
September 175 cubic metres
October 108 cubic metres
November 64 cubic metres
December 62 cubic metres

Consequences of wetter weather

In 2011, the amount of snowmelt in the Prairie Provinces was much greater than in 2006, and approximately double that of 2001, when the overall risk values were much lower. The record snowmelt coincided with above-average spring rainfall, leading to record runoff levels and significant flooding throughout the southern Prairies. This wet weather increased the coliform risk values for the Prairies that year and likely affected the national trend for this indicator. Conversely, the very low risk values in 2001 can be partially attributed to the exceptionally low amounts of runoff from both snowmelt and rainfall in the Prairies that year, which reduced the risk of water contamination.

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 a high level throughout the year (Figure 6). On the Prairies, spring snowmelt runoff represents almost the entire annual runoff and accounts for almost 90% of the risk value.

Figure 6: Daily mean coliform population intensity (measured in coliform forming units [CFU] per hectare [ha-1] times 10,000,000,000 [×1010]) on pasture, 2011
Description of this image follows.
Description - Figure 6
Month Western Canada
(British Columbia, Alberta, Saskatchewan, Manitoba) pasture
Eastern Canada
(Ontario, Quebec, New Brunswick, Nova Scotia, Prince Edward Island, Newfoundland and Labrador)
January 5.00451 CFU × 1010 0.78731 CFU × 1010
February 4.95069 CFU × 1010 0.79594 CFU × 1010
March 5.50654 CFU × 1010 0.56508 CFU × 1010
April 2.32292 CFU × 1010 0.33038 CFU × 1010
May 2.46485 CFU × 1010 6.16050 CFU × 1010
June 5.11137 CFU × 1010 10.28088 CFU × 1010
July 3.81253 CFU × 1010 7.04350 CFU × 1010
August 3.85001 CFU × 1010 8.11448 CFU × 1010
September 2.24561 CFU × 1010 7.89011 CFU × 1010
October 1.55513 CFU × 1010 0.22386 CFU × 1010
November 3.07827 CFU × 1010 0.30471 CFU × 1010
December 3.44495 CFU × 1010 0.46834 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. The largest volume of stored manure is spread in the spring before planting (March to April). Other major applications occur in June following forage harvest, as well as in the fall (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.

Figure 7: Daily mean coliform population intensity (measured in coliform forming units [CFU] per hectare [ha-1] times 10,000,000,000 [×1010]) on cropland, 2011
Description of this image follows.
Description - Figure 7
Month Western Canada
(British Columbia, Alberta, Saskatchewan, Manitoba) pasture
Eastern Canada
(Ontario, Quebec, New Brunswick, Nova Scotia, Prince Edward Island, Newfoundland and Labrador)
January 0.00002 CFU × 1010 0.01965 CFU × 1010
February 0.00000 CFU × 1010 0.00070 CFU × 1010
March 1.31806 CFU × 1010 2.61003 CFU × 1010
April 1.22346 CFU × 1010 2.17478 CFU × 1010
May 0.01745 CFU × 1010 0.26856 CFU x 1010
June 0.00000 CFU × 1010 0.00000 CFU × 1010
July 0.00000 CFU × 1010 0.00000 CFU × 1010
August 0.00026 CFU × 1010 0.00000 CFU × 1010
September 0.05321 CFU × 1010 0.03639 CFU × 1010
October 0.08204 CFU × 1010 0.18158 CFU × 1010
November 0.13552 CFU × 1010 0.00552 CFU × 1010
December 0.00127 CFU × 1010 0.11255 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.

How performance indices are calculated

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). The equation is simply "(% in poor class multiplied by .25) plus (% in moderate class multiplied by .5) plus (% in good class multiplied by .75) plus (% in desired class)." As the percentage of land in the "at risk" class is multiplied by zero, it is not included in the algorithm.

The table below shows the index classes. The index uses the same five-colour scheme as the indicator maps whereby dark green represents a desirable or healthy state and red represents least desirable or least healthy.

The index classes
Scale Colour scheme Class
80-100 Dark green Desired
60-79 Light green Good
40-59 Yellow Moderate
20-39 Orange Poor
0-19 Red At risk

The index tends to aggregate and generalize trends and so should be viewed as a policy tool to give a general overview of state and trend over time.

Related indicators

Additional resources and downloads