By Laura Coup, Clean Water Institute Intern, Summer 2022
According to the EPCAMR, when one inch of rain falls on an acre of impervious surface, such as a parking lot, it results in 27,000 gallons of stormwater runoff. In comparison, when one inch of rain falls on one acre of forest or wetland, it produces only 750 gallons of runoff. Impervious surfaces like roads, roofs, sidewalks, and driveways can result in large amounts of stormwater runoff in residential areas. This runoff carries fertilizers, pet waste, oil, pesticides, viruses and bacteria, and other harmful pollutants down storm drains and then into streams and rivers. The EPA estimates that pollutants carried stormwater runoff makes up around 70% of all water pollution. These pollutants have negative impacts on both the drinking water supply and aquatic life.
Homeowners can help reduce the stormwater runoff from their property by installing rain barrels and/or rain gardens. Rain barrels are a fairly low cost and simple way to reduce your runoff. A rain barrel is typically made using a 50- to 80- gallon plastic barrel and should be installed on a sturdy base platform along your home with the down spout going into an opening on the top of the barrel. There should be a spigot near the bottom to drain water for use and an overflow hose near the top. The average rain barrel costs between 100 to 200 dollars; however, the cost can be reduced when homeowners construct their own barrel.
Rain barrels capture stormwater runoff from the roof of your home and temporarily store it for future use. This rainwater can be recycled and used to water gardens, lawns, or plants or used for outdoor cleaning, among other uses. According to Penn State Extension, lawn and garden care accounts for around 30 percent of our average daily water usage. Rain barrels decrease the amount of household water used for these purposes, and in turn can help reduce water bills. Using rain barrels also allows stormwater to slowly soak in and infiltrate the ground rather than quickly runoff and carry pollutants into storm drains.
Rain gardens are another way to reduce the amount of stormwater runoff flowing from your property. According to the Natural Resources Conservation Service, the size of a rain garden should ideally be between 5- and 10-percent of the area of the impervious surface it is receiving runoff from. Rain gardens are typically planted in depressions or low areas of the ground, and can be located near downspouts, driveways, sidewalks, in yards, or anywhere where they can receive runoff water from impervious surfaces. They should, however, not be placed within 10 feet of building foundations and/or basements. The Groundwater Foundation recommends that your rain garden be longer than it is wide, and positioned perpendicular to the slope of the land so that it is able to catch as much runoff as possible. The deepest part of a rain garden should only be around six inches in order to allow the rain garden to properly drain between rain events. The depth should vary throughout the rain garden to allow water to flow and slowly fill up the garden.
Rain gardens ideally contain native species of flowers, shrubs and other plants. Native plants tend to have root systems better adapted to utilizing the water and nutrients available in local soils. Native plants will also help your rain garden attract beneficial birds, butterflies, and insects. Penn State Extension offers an excellent resource for determining which native plants can be beneficial additions to your rain garden (https://extension.psu.edu/rain-gardens-the-plants). Self-installed rain gardens generally cost between $3 to $5 per square foot, while the cost may increase to near $10 to $15 when using a landscaping company.
Rain gardens collect runoff during rainfall events and allow that water to percolate and slowly infiltrate the ground, rather than entering storm drains. In this process, the rainwater runoff is filtered by the plants and soil and helps recharge groundwater aquifers. The Groundwater Foundation estimates that rain gardens are effective in removing upwards of 90% of chemicals and nutrients and 80% of sediments from stormwater runoff. These pollutants would otherwise enter storm drains and go into our streams and rivers. Rain gardens also allow much more water to soak into the ground than a typical lawn.
One inch of rain graphic by EPCAMR