A guide to how rain gardens reduce water pollution and how to build one
What's a rain garden? Well, we're glad you asked! Rain gardens are not very well known but they are becoming more and more popular for their ability to reduce water pollution. The basic premise of a rain garden is that a basin filled with native plants captures water as it flows through your yard and filters out pollutants through the soil and plant roots before reentering the groundwater. Rain gardens are incredible, not only for being a great way to clean our water runoff, but they are aesthetically beautiful and create habitats for so much wildlife!
Keep reading to learn more about how rain gardens can purify water in your local ecosystem and how you can build one of your very own!
How Your Home Causes water pollution
When we think of water pollution we usually think of culprits like landfills, farming runoff, and industrial chemical waste. As it turns out, the runoff from different places at our homes are also a big part of the problem! Everytime it rains, water runs off surfaces like driveways, roofs, patios, and even our lawns. A lot of the time these surfaces can carry dirt particulates, chemicals, oils, garbage, and different types of bacteria and all of this can end up in our water. The United States Environmental Protection Agency estimates that pollutants carried by rainwater runoff accounts for 70% of all water pollution (1).
It's also important to mention that this water runoff from our homes and other areas can make its way into nearby streams, lakes, oceans, and even our drinking water reservoirs (3). This is a major problem for the health of the surrounding wildlife and even us humans. A lot of the pollutants that are running off our driveways, roads, and roofs are toxic industrial chemicals and heavy metals from cars, as well as agricultural pesticides and waste. When these chemicals get into our water systems and the surrounding vegetation, animals eat the plants or drink the water and are exposed to many harmful chemicals that can cause a variety of health problems (7). When it comes to humans, the safety of our drinking water is a major concern. Thankfully we have water treatment plants to clean out the harmful chemicals and materials, however, there are still some chemicals and pesticides that are tricky to remove from our water sources. Water treatment plants do the best they can to remove most of the pollutants, but it is not a perfect process (8). Because of this, we can be exposed to these nasty pollutants through drinking contaminated water or when we play in our local lakes, streams, and beaches.
The good news is that we have the power to reduce the amount of water pollution that comes from our homes by planting a rain garden!
So what exactly are rain gardens?
A rain garden is a depressed area in the landscape filled with grasses and native plants that works to collect the runoff from all of the areas on your property. Not only does a rain garden collect all of the water runoff, it also helps filter out the pollutants collected along the way. This filtration process is done by using the plants and soil in the garden. As the water moves farther into the ground more of the contaminants are removed by the soil and plant roots and eventually the water will be able to recharge ground water aquifers. Sounds like a win win situation (1)!
Some of the other benefits of rain gardens include protection against floods and the habitat they provide. Water collects in the rain garden due to its lower elevation and acts as a drainage site for the diverted water. The water is then rapidly absorbed by the plants dramatically reducing the amount of water in your yard more efficiently after a storm (3)! This is where the plants in your rain gardens might differ slightly from your average garden plants. The most common plants used in rain gardens are able to tolerate long wet periods and long drought periods to be able to survive when there is rain and when there isn't (9). The plants have an added function as habitat for beneficial wildlife such as butterflies, bees, birds, and other small animals (4). Rain gardens protect our environment, our homes, our drinking water, and wildlife! Who wouldn't want that?
So... Do you want to build a rain garden?
We know this might seem a little daunting, but we promise it's easier than it looks and will be so worth it!
- Find a Location
The first step in creating the perfect rain garden is the planning phase. To pick a location for the rain garden many people conduct a rainy day survey. Is there a part of your yard that always collects water after a storm or where the soil stays extra wet for longer? That's a good place to start. You can also draw a rough map of your home and landmarks like trees, patios, and driveways, as well as how the water flows through your property when it rains. Typically areas with slight slopes or near gutter drain pipes are great places to plant a rain garden.Once you have picked a location that you believe will capture the most water runoff the next step is to determine the size you want your garden to be. Most rain gardens range from 150 - 480 sq ft and are at least 6 inches deep. Rain gardens can be really big or really small; design them to fit your needs and how much space you have available.
2. Pick Your Plants
The final step for planning is to pick your plants! When picking the plants for your rain garden you want to look for native perennial flowers, grasses, and shrubs that will survive in the amount of sunlight your rain garden is exposed to and the different weather patterns of where you live. The most common layout for plants in a rain garden is to have perennial flowers and natives that can tolerate lots of water in the center. Then around the center you want plants that can sometimes tolerate standing water but usually prefer to be dry like grasses, and finally around the edges use plants that prefer mostly dry soil (12). Talking with people from your local plant nurseries or just searching for native plants in your area can help you determine which plants will be best suited for your needs! (2) Some helpful online resources for native plants in your area and good plants for rain gardens are linked here!
3. Plant Your Rain Garden
Once you have completed all of the planning and preparation, the next step is to start digging. As we mentioned, a rain garden should be at least 6 inches deep for optimal water capture and drainage. Once you dig out your area make sure to create a gentle slope from the top to the center to help hold the water in. Once the area is prepared place your plants in the soil and pack them in. After planting, it is recommended that you place mulch over the top of the exposed soil to prevent weeds and to help with water drainage. This will save you a lot of time and energy down the line! The final step is to add any design elements like rocks and stones to the garden and water all of your plants in. Voila, you have a beautiful rain garden (5)!
If you need a slightly more in depth look at how to build your rain garden and different designs, we have added some links to help you out. Check out these links:
- Gaffield, S. J., Goo, R. L., Richards, L. A., & Jackson, R. J. (2003). Public Health Effects of Inadequately Managed Stormwater Runoff. American Journal of Public Health, 93(9), 1527–1533. https://doi.org/10.2105/AJPH.93.9.1527