How Lawns and Gardens Can Affect Payette Lake

Homeowners commonly over-apply fertilizer, adding much more nitrogen and phosphorus
to lawns and gardens than can actually be absorbed by plants and soil. Many residential
lawns along Payette Lake go right up to the lake shore with no natural vegetation or beach
space to serve as a buffer. Over-watering acts in tandem with over-fertilizing to add excess
nutrients to the lake. Pesticides, herbicides, and other chemicals on lawns and gardens can
also leach into the lake by traveling through the soil and into the shallow water table along
the shore. All of these actions can threaten recreational and drinking water uses in the lake.

Lawns and gardens near Payette Lake or any of its tributaries must be carefully planned
and maintained to prevent contamination of surface water and groundwater. Native
vegetation should always be considered as a quality alternative to cultivated lawns and

Improving Lawn & Garden Management

Before starting any landscaping activity, stop and think about potential risks to water quality
in Payette Lake and its tributaries. Please stay aware of potential problems caused by
pollution from lawn and garden chemicals and soil erosion. The conditions described below
make it more likely that pollution is entering the lake from your property. When the following
conditions are present, you need to take extra care.

If there are areas of exposed soil on your property, soil erosion is a risk. Coarse-textured
soils such as sand or sandy loam increase erosion risk; areas of your property that slope
toward surface water also increase that risk. Impermeable surfaces such as sidewalks and
driveways may increase stormwater runoff to the lake. Lawns and gardens near the shore
are more likely to contribute pollutants directly to the lake.

Risks from Pesticide and Herbicide Use on Lawns and Gardens

Pesticides and herbicides can harm or kill beneficial insects and earthworms in your lawn
and garden. Humans, pets, and wildlife coming into contact with treated plants and soils
can also be harmed. Pest resistance to applied chemicals increases over time, making pest
control much more difficult in the future. Runoff from areas treated with herbicides or
pesticides, during rainfall or from over-watering, can damage aquatic ecosystems and
residential drinking water sources. Pesticides and herbicides can cause chronic health
problems in humans.

Take Action

  • Minimize use of pesticides and herbicides; follow label directions and instructions for use.
  • Consider natural alternatives to pesticide/herbicide use; call the Valley County University of Idaho Extension for information (208-372-7190;
  • Identify whether the problem in the lawn or garden is being caused by an insect, fungus, disease, or other source.
  • Determine whether the problem causes environmental harm or plant damage or is merely aesthetic.
  • Have a diversity of plants in your gardens for a balanced ecosystem and natural pest control. (Mix up the flowers and vegetables, for example.)
  • Rotate garden crops each year to reduce pest damage and minimize disease.
  • Maximize conditions for healthy plant growth by choosing climate-appropriate plants with pest and disease resistance.
  • Protect and attract beneficial insects by providing diverse garden habitat and by recognizing their larvae and eggs in order to not harm them.
  • Use nontoxic biodegradable pesticides or herbicides.
  • Do not apply chemical treatment in windy conditions or prior to irrigation or predicted rain.
  • Do not pour surplus chemicals down a drain, on ground or in surface waters. Instead, hold toxic and hazardous materials for disposal during the Valley County hazardous material collection program each year, typically in August. Call 208-634-7712 for current information.

Risks from Fertilizer Use on Lawns and Gardens

Nitrates and phosphorus, the two main ingredients in most fertilizers, can contaminate surface water and groundwater when overapplied or when your landscape is overwatered. Nitrates and phosphorus can leach into groundwater wells used for drinking water (even concentrations of 10 parts per million are hazardous to pregnant women and can be fatal to infants.) Over-application of fertilizers can cause disease in lawns and can also promote weed growth. Nitrates and phosphorus that enter the lake from lawns and gardens cause excessive aquatic weed growth, which is particularly harmful to the lake’s ecosystem and to water quality.

Take Action

  • Landscape with native plants which do not require applications of fertilizer.
  • Have your soil tested to determine how much fertilizer is needed. Use alternative forms of fertilizer, such as grass cuttings, compost, or composted manure.
  • If chemical fertilizer is used, select slow-release (water insoluble) forms.
  • Apply fertilizer according to label instructions and follow precautions; purchase only as much as needed and dispose of containers properly.
  • Water your lawn and garden lightly after fertilizing, but do not allow excess water to run off.
  • Do not apply greater than 3 pounds of actual nitrogen per 1,000 square feet of lawn per year; make several applications over the growing season rather than one single application.
  • Never apply any fertilizer within 100 feet of Payette Lake or its tributaries.

Risks from Irrigating Lawns and Gardens

Use water wisely on lawns. Over-watering may cause pesticides, fertilizers, and sediment to either runoff into surface waters or leach into groundwater, potentially contaminating drinking water sources.

Take Action

  • Retaining native vegetation on your property is the recommended strategy; this will greatly reduce the need for irrigation.
  • Plant lawns with drought-tolerant grass varieties; an excellent mixture for around Payette Lake is bluegrass, creeping red fescue, and perennial rye.
  • Don’t over-water. Over-watering can significantly contribute to the transport of unwanted nutrients and sediments into Payette Lake.
  • Consider that established lawns only need 1-2 inches of water per week.
  • Leaving grass clippings on the lawn provides natural fertilizer as well as shading the soil surface and retaining moisture, thus reducing the amount of watering needed.
  • If your runoff from irrigation crosses impermeable surfaces and is not controlled, sediment and road chemicals may be transported into surface water.

Risks from Erosion

Surface waters can be contaminated by soil particles that are washed or blown into the water. In addition to pollution from sediment, phosphorus and other chemicals washed off of roadways, driveways, and lawns can be carried by soil particles into the lake and its tributaries.

Take Action

  • Minimize areas of exposed soil by maintaining native vegetation or dense turf.
  • Minimize impermeable surfaces such as roads, driveways, roofs and parking lots.

Construct a swale or an earth berm (a small mound of earth) near the lake shore to minimize the possibility of runoff entering the lake. The berm should run parallel to the shore in order to block runoff effectively, and it should be solidly compacted so that it does not disintegrate during rainfall, snowmelt or irrigation. In winter, preserve ice ridges to serve 3 the same function.

Additional Strategies

The most efficient strategy for protecting surface water from contamination due to lawn and garden activities is to create or enhance a buffer zone of native trees, shrubs, and grasses between the lake and your lawn. The most effective buffer zone is 50-100 feet wide. This single action will help preserve water quality by filtering rain, snow, and irrigation runoff, as well as by absorbing nutrients from shallow groundwater.

Take Action

  • Rake dead leaves and brush away from the water; compost vegetation in a sturdy structure away from the shoreline. Avoid leaf blower use near the shoreline to keep debris from entering the lake.
  • Never dump leaves or vegetative debris into the lake or any stream. Dumping organic material into the water releases nutrients and organic acids that use up valuable oxygen needed by fish.
  • Avoid burning on the beach or near the shore because the remaining ash is highly alkaline and contains soluble nutrients. If it washes or blows into the lake, it can change the pH of the water and promote growth of undesirable plants and algae.
  • Never use pesticides, herbicides, insecticides, or fertilizers within 100 feet of the lake or its tributaries.