Some Real Numbers

I thought it would be helpful to those considering a rain garden and whether it's really worth the effort, to tell you what impact our rain garden has.

Between the roof of our home, a small what I call brick 'cottage and the porch roof, we have 960 square feet of impervious surface. Since 1000 square feet of impervious surface generates 638 gallons of water during a 1-inch rain event, our roof generates 613 gallons of water (96%) in that 1-inch rain event. We fill 4 rain barrels for a total of 260 gallons of rain water retention. The remaining 353 gallons is filtered through our rain garden and returned to the water table. I checked the paper and on June 4th, the average year-to-date rainfall would be 18.47 inches. This means that we have filtered and returned to the water table 6520 gallons of clean water. I looked at my city water bill and that amounts to our water usage for a family of 3 for 2 months.

This doesn't take into account the fact that total water removed from the storm water system was 11,322 gallons that didn't dump into the creek across the street and erode it's banks. Now if just 10 homes out of our neighborhood of about 1200 had rain gardens, we'd eliminate 113,221 gallons of storm water run off and return that amount to the water table as clean water.

I think you begin to see the impact this type of gardening can have and how it can contribute to a regions goal of reducing the contamination going into reservoirs and lakes used for public water supplies.