Rain Gardens and Groundwater
What is a Rain Garden?
A rain garden is a garden that collects and filters water before it absorbs back into the ground. They are beneficial in areas that have larger surfaces that water cannot permeate through to get back into the ground. Rain gardens help conserve and recharge our groundwater.
How do Rain gardens affect ground water?
A study done at the University of Wisconsin- Madison shows that rain gardens are effective at replenishing our dwindling ground water supplies.
How? The rain garden is composed of two parts. The top layer is soil where the plants are planted and collect rainwater. The layer below that is a permeable layer of gravel and sand. This layer helps hold the water as it seeps into the subsoil beneath it.
Rain gardens are very effective in urban and suburban areas where most surfaces are water impermeable and rainwater flows into sewer and drainage systems rather than back into the land.
Surprisingly, rain gardens do not need to be large to be effective. The study concluded that to be most effective the rain garden only needs to make up about 10% of the covered area to effectively capture water and help it get back into the ground. The smaller area helps force rain into the ground faster rather than when spread out over a large lawn and most water is taken by grass, plants, and evaporation before reaching the subsoil.
Why is it important to care for ground water?
Our ground water is precious and limited. It is important to help rainwater get back into the earth to replenish our water supply.
How and where should I plant my Rain Garden?
When planning your rain garden it is important to place them at least 10 feet away from building or homes to avoid water seepage issues. You also want to make sure it is on a slightly sloped area where water does not puddle, this helps with increases absorption into the ground. Rain gardens also do well in sunny or partly sunny areas.
Make sure before you start digging to call Dig Safe to make sure you won’t hit any underground utility lines, 800-344-7233. It is also important not to place your garden over septic tanks or drain fields.
The best areas have sandy soil because it is easier for the water to permeate through. It will be more difficult and be more steps if you want to plant in a spot with clay soil.
The size of the rain garden can be big or small depending on the space. The University of Massachusetts Amherst has a chart of potential dimensions based on the size of area you want to drain.
What are good plants to add to Rain garden?
A few plants that are recommended by Purdue for a rain garden are;
Big Bluestem, Indiangrass, Little Bluestem, Various Sedges
Aster, Black-Eyed Susan, False Indigo, Flag Iris, Goldenrod, Great Blue Lobelia, Ironweed, Joe Pye Weed, Liatris, Penstemon, Swamp Milkweed
American Beautyberry, Arrowwood Viburnum, Bottlebrush Buckeye, Buttonbush, Oakleaf Hydrangea, Summersweet Clethra, Sweetspire
Bald Cypress, Fringetree, Ginkgo, Red Maple, River Birch, Sycamore
UMass also has a list of tress, perennials, and ground covering plants on their website that would work well in your rain garden. They have also noted where to best plant them, how much moisture they need, how large the plant tends to get, and a few other good to know facts you might like to note.