Prevention of Water Contamination by Pesticides

Bob Buchanan, Regional Engineering Technologist, Alberta Agriculture, Barrhead

The hydrologic cycle.

Pesticides can enter groundwater by infiltration through the soil or by accidental discharge into wells. They can enter surface water (lakes, streams and ponds) by runoff, soil erosion, spray drift, misapplication and spillage (as illustrated in the accompanying diagram). Pesticide users should take special care to prevent contamination of water supplies.

Preventative Measures to Protect Water Sources from Pesticide Contamination

1. Use pesticides only when required. Follow the label closely and keep spray equipment maintained and calibrated.
2. Learn about soil mobility and persistence of available pesticides. Consult Agriculture or Environment specialists and check the label for precautionary statements.
3. Assess the susceptibility of the soil to erosion and pesticide leaking. Soil texture, organic matter and site characteristics should be considered.
4. Consider the location of the water table, used or abandoned wells and surface waters. Create a spray free zone of 10 feet (30 metres) from these sources. Provincial government approval is required for spraying within 100 feet of open water bodies.
5. Check weather predictions prior to spraying. Avoid spraying for one day prior to predicted rain. Do not irrigate sprayed areas to avoid runoff.
6. Use application procedures which reduce spray drift.
7. Do not fill spray tanks directly from any water source. Use a nurse tank and do not wash or transport spray equipment in or through a water body.
8. Store pesticides in a separate room away from water supplies. The floor should be impermeable with no floor drain.
9. Triple or pressure rinse all pesticide containers and add to spray tank. Dispose of containers at an approved collection site in your area.
10. Use common sense to plan pesticide use and handling procedures so as to prevent the contamination of water.

Further information is contained in a fact sheet from Alberta Environment. The fact sheet was prepared by Robert Burland, an Aquatic Specialist in Lethbridge, Alberta.