Controlling Runoff from Confined Livestock Areas

Manitoba is very fortunate to have an ample supply of good-quality surface water. Many communities rely upon surface water for their drinking water supply, as well as for recreational purposes such as swimming and boating. Agricultural uses include watering livestock, irrigating crops and processing food. And, equally important, water is used by wildlife and is home to many aquatic organisms. However, often these same users cause surface water quality problems. Several agricultural practices can harm surface water quality. Allowing contaminated runoff to flow into surface watercourses is one of them.

 

What is a "confined livestock area"?

A confined livestock area, as defined by the Livestock Manure and Mortalities Management Regulation, is "an outdoor, non-grazing area where livestock are confined by means of fences or other structures, and includes a feedlot, paddock, corral, exercise yard, holding area and hooped structure."

 

Why worry about runoff?

Runoff from a confined livestock area could harm water quality if it is allowed to enter a surface watercourse. Excessive amounts of plant nutrients, such as nitrogen and phosphorus, will increase aquatic plant growth if they enter a surface watercourse. Nitrogen, in the form of ammonia, is toxic to aquatic life. The organic matter in runoff acts as a "fuel" for microscopic aquatic organisms. The breakdown of this organic material results in a reduction of the amount of dissolved oxygen, sometimes killing fish. Sediment carried in the runoff may contribute to silting, interfering with fish habitat by smothering spawning areas. Runoff may also contain pathogenic (disease-causing) organisms, which if present in sufficient numbers, create a health hazard. For these reasons, contaminated runoff must not be permitted to enter a surface watercourse.

 

How runoff can be prevented from entering a surface watercourse

The first step in runoff control is to prevent off-site or uncontaminated runoff from flowing into the confined livestock area. It may be necessary to construct diversion ditches or berms to direct clean water away from the area.

The next step is to ensure that all livestock pens are graded, so that the on-site runoff is channelled to a central collection or holding pond. Depending on the site, it may be necessary to provide more than one collection basin. Recommended pen slopes are from two to four per cent. Diagonal pen slopes are often provided to ensure proper pen drainage, as well as adequate ditch slope.

The collection basin's minimum capacity must not be less than 7.5 cm (3 in) of runoff from the confined livestock area. Its maximum capacity must not be greater than 15 cm (6 in) of runoff from the confined livestock area.  In addition, a freeboard of 30 cm (12 in) must be provided.  Allowing clean water from outside the facility into the confined livestock area will mean that a larger than necessary collection basin will be required.  The collection basin must be emptied as soon as possible after spring snowmelt or heavy rainfall to be ready for the next runoff event.

Larger facilities should consider using a two-stage collection basin. The first stage is a settling basin, which allows most of the solids in the runoff to be separated from the liquid. The settling basin should be relatively shallow, from 0.6 to 1.2 m (2 to 4 ft) deep. It should have an area of at least 2.5 per cent of the total collection area. The second stage is then the main collection basin.

A runoff collection basin must only be used if it will not result in groundwater contamination. It must be constructed and operated in accordance with the Livestock Manure and Mortalities Management Regulation. Construction details are available on Manitoba Conservation's web site.

 

Disposing of runoff

The most practical method of runoff disposal at this time is to spread it onto cropland. The crops will use the water and plant nutrients in the runoff. The organic material will add to the soil organic matter, helping to improve the soil. Any pathogenic organisms will be destroyed: by drying out, by exposure to sunlight or by other organisms in the soil.

A basic irrigation system should be adequate for most smaller operations. Larger facilities, such as commercial feedlots, may wish to hire a custom applicator to dispose of their collected runoff.

In order to prevent surface runoff, the rate of application should not exceed the rate of soil infiltration. In addition, the application rate must not exceed the annual crop fertilizer needs. On average, runoff from confined livestock areas contains 0.4 per cent nitrogen and 0.1 per cent phosphorus. In all cases, it is important to prevent contaminated runoff from entering any surface watercourse when spreading it onto cropland.

Other methods of runoff disposal

Constructed Wetlands

It has long been known that natural wetlands have the ability, by way of both physical and biological processes, to filter and cleanse contaminated water. A constructed wetland is a man-made wetland built to treat contaminated wastewater or storm water runoff. Two wetlands were constructed by the Prairie Farm Rehabilitation Administration (PFRA) in 1996 and 1997 to test their effectiveness in treating runoff from beef cattle operations. Results in PFRA's extensive evaluation are available here. Producers interested in setting up constructed wetlands to treat runoff from their operations should obtain technical assistance before beginning construction. In addition, permission to discharge the treated effluent must be obtained from Manitoba Conservation.

Vegetated Filter Strips

Another way of treating contaminated runoff is to use a vegetated filter strip (VFS). Ontario has evaluated the use of vegetated filter strips to treat runoff from confined livestock areas and solid manure storage areas. A VFS is "a system in which a vegetative area is used for treating runoff by infiltration, dilution, filtration and absorption of pollutants". The size of the VFS depends on the volume of runoff to be treated. The vegetated area should be sloped from 0.5 to 4 percent. Widths start at 9 m (30 ft), with lengths from 90 m (300 ft) to 275 m (900 ft. Crops grown in the treatment area must be able to tolerate both wet and dry conditions - examples are reed canary grass, brome grass and orchard grass.

Copies of Ontario's Vegetated Filter Strip Design Manual are available here.  Vegetated filter strips have not been evaluated under Manitoba conditions, so producers considering using a VFS to dispose of runoff form a confined livestock area are encouraged to "do their homework" before establishing a vegetated filter strip.

 

Runoff Control Information

• Farm Practices Guidelines for Beef Producers in Manitoba
• Farm Practices Guidelines for Dairy Producers in Manitoba
• Consulting Engineering Firms (Look in the Yellow Pages under Engineers – Consulting)
• Protecting Your Shorelands for Better Farming and Ranching, and Healthier Fish Habitat (available from Fisheries and Oceans Canada)
• Troubled Waters: Threats to Fish Habitat in the Prairie Provinces (available from Fisheries and Oceans Canada)

 

For further information, contact your GO Representative.