South Platte River (14123 bytes)

The Water You Contaminate Could Be Your Own

By Bonnie Ennis, Colorado State University Cooperative Extension Agent, horticulture

What comes around goes around, and nothing applies to this theory more clearly than the water we use and drink.

Overwatering and mis-use of chemicals contaminate water supplies. Home gardeners can play a key role in protecting water quality by making wise decisions about fertilizer and pesticide use, as well as about watering practices.

Why home gardeners? Recent studies show that homeowners use more pesticides per acre than farmers use on their fields. One study indicates that 27% of all pesticide use is in urban areas. Such studies de-bunk the notion that agriculture is the only culprit in the war of words about chemicals and the environment.

The concept is simple: Water falls as rain and snow. It seeps into the groundwater or flows directly into streams, taking chemicals with it. Ultimately, it is withdrawn, treated and used for drinking or landscape irrigation. Wise management in the home landscape can reduce potential water quality problems and create safer supplies.


Plants need water for moisture and to dilute and carry fertilizers and pesticides into root zones.

Overwatering carries fertilizers and pesticides beyond root zones into ground water stored in alluvial or bedrock aquifers below the soil surface. Water in these aquifers can interact, sharing chemical contaminants. Aquifer water also interacts with stream water.

Overwatering also results in storm drain run-off. This run-off flows untreated through underground pipes to the nearest creek or river, again carrying pesticides and fertilizers.

Down the Home Drain

Pesticides and fertilizers flushed down indoor drains flow to the nearest sewage treatment plants.Sewage treatment plants do not remove pesticide or fertilizers. DO NOT DUMP PESTICIDES OR FERTILIZERS DOWN INDOOR DRAINS.

Nitrate nitrogen is a common component of landscape fertilizers which, in concentrations greater than l0 milligrams per liter of water, is toxic to pregnant women and small children. Treated household waste effluents in the South Platte River already create levels of 20-30 milligrams of nitrates per liter of water. Nitrate fertilizers flushed down home drains will only increase these high nitrate levels.

Who Uses Groundwater and Open Channel Water?

The answer is almost everyone. Glendale depends l00 percent on wells that tap into the Cherry Creek alluvial aquifer. Thornton, Northglenn and Arvada supplement their water supply from wells drilled into other aquifers. Chemicals, that leach through the soil, can contaminate these wells.

Arvada, Northglenn, Thornton and Golden also take water from Standley Lake. The lake is fed by Clear Creek, a stream that receives both untreated storm drainage and direct soil run-off that contains pesticides and fertilizers.

What Can We Do to Help?

As home gardeners gear up for the summer growing season, we can think twice about use and disposal of fertilizers and pesticides. To prevent chemical contamination, water lawns following ET recommendations from the Denver Water Department. Or water only when soil is dry and then just until root zones are moistened. Turn off water before run-off occurs. Allow water to soak into soil before re-applying. To reduce run-off, aerate heavy soils, especially on slopes.

Use great caution as you dispose of chemicals. For a safer environment:

  • Use chemicals according to label directions.

  • Water only as needed.

  • Do NOT dump chemicals down the drain, in the garbage or onto the ground.

Photograph courtesy of Judy Sedbrook.

Back to Gardening

Back to Home



Ask a Colorado Master Gardener | Calendar | Children | Container GardeningCSU Fact Sheets
Credits | Diseases | FAQ | Flowers | Fruits | Gardening | GlossaryHouseplants | Insects & Pests
Lawn & Grasses | Links | New to Colorado | PHC/IPM | Soil | Shrubs | Trees
Vegetables | Water Gardening | Weeds | What's New | Who We Are | Xeriscape


line4.gif (1411 bytes)

Contact Us | Disclaimer | Equal Opportunity

CSU/Denver County  Extension Master Gardener 2010
888 E. Iliff Avenue,  Denver, CO 80210
(720) 913-5278


Date last revised: 01/05/2010