Two major sources of non-point source pollution are construction and yard chemicals. The average homeowner has little control over what the builder did to reduce runoff during the construction of their home, there are tips and tools used in the construction of large developments that every home owner can use to reduce their environmental impact.
Non-point source pollution is defined by the U.S. Environmental Protection Agency as:
Unlike pollution from industrial and sewage treatment plants, nonpoint source (NPS) pollution comes from many diffuse sources. NPS pollution is caused by rainfall or snowmelt moving over and through the ground. As the runoff moves, it picks up and carries away natural and human-made pollutants, finally depositing them into lakes, rivers, wetlands, coastal waters and ground waters. (EPA 1)
Read more about the affects of eutrophication on coastal waters at the World Resourses Institute. If the same excess amounts are from "Weed and Feed" containing Atrazine, the effects on shallow aquifers can be pronounced. If you want to know the health effects of atrazine, EPA has produced this factsheet on atrazine (EPA 2).
Reading the bag before applying fertilizer is important. It will tell you how much to apply, and when to apply it in relation to the next rain. Do not exceed the recommended application rate. But how often should a homeowner fertilize their lawn?
The fertilizer companies recommend multiple applications per year, with reapplication as early as every 30 days. Let the grass tell you when it needs more food. If it is a normal rainfall year, and your lawn is looking brown, an additional dose of fertilizer may be necessary, but most grasses will be fine with one or two applications each year.
Phosphorus is extremely prone to runoff, unless your grass looks like it needs water or is turning purple, try using a fertilizer that contains no phosphorus.
A bag of fertilizer will have three numbers separated by dashes. This is the percentage each of nitrogen - phosphorus - potassium (N-P-K) in that order. 13-13-13 fertilizer, contains 13 percent by weight of (N-P-K), while 23-0-4 contains 23 percent nitrogen, 4 percent potassium, and no phosphorus.
Homeowners who use "weed and feed" can use products that do not contain atrazine. Or if there are only a few weeds, try removing weeds by hand.
The type of grasses used for lawns can also have a major impact on the need for chemicals and watering, but that is a topic for a separate article.