Fixing "Impaired" water sources

From The News & Observer's June 25, 2009 Editorial section: Title - A cleaner Falls, faster. Falls Lake is the drinking water resource for 435,000 in Wake County, North Carolina. Unfortunately, under federal clean water standards, the lake is impaired. The editorial goes on to state that high levels of both nitrogen and phosphorus are causing increases in algae in the lake. You know what algae looks like, that sickly green stuff that clouds the water or if enough exists, floats like large clouds on the surface. This makes the water harder to clean for drinking purposes.

And of course, the source of this problem originates upstream, in this case, Durham County whose rivers and streams feed both Falls and Jordan lakes.

The editorial acknowledges the difficulty of the work necessary to reduce these levels, especially with a state budget crisis.

So are our lush green lawns causing problems? Well, in a word yes.

The importance of rain gardens becomes clearer now. We don't have to wait for our officials to take action, because we can start solving the problem right now by installing a rain garden in our yard. No, it won't be a total solution. Businesses large and small will also need to create mechanisms to catch their rain water and prevent it from entering our waterways.

But we can start. Think about it.

Visualize the volume

It's pretty hard to visualize how much space 6500 gallons of water would fill for the rain water we have diverted from the storm water system so far this year.

Out of curiosity, I checked out how many gallons of water it takes to fill a small swimming pool that is 12 X 24 with an average depth of 5.5 feet. Water capacity for that size pool is 12,420 gallons. So far this year, we could have filled half a swimming pool with the water that didn't go into the storm water system.

If you've ever watched America's Funniest Home Videos, you have seen what happens when the walls of an above ground pool collapse. Everything including people get swept away with the surge. Multiply that by 10 for impact. This gives you some idea of the benefits a rain garden provides for local streams that aren't being impacted by our run-off. Again, if 10 houses in our neighborhood did this, we would have prevented 4 or5 swimming pools worth of water from hitting the storm water system and the creek across the street. We would also have stopped the chemicals those waters contained from landing in our water sources.

Think about it.

seedling or weedling

In the Ongoing Care section of my book, I talk about differentiating tiny seedlings of the plants you want from the unwanted plants that sprout in your rain garden soil mix. Here is a tiny Baptisia australis (Blue Wild Indigo) growing among Sedums and Houttuynia. Although tiny, the leaves match exactly that of the parent plant. When in doubt, let it grow a season and then check it against the parent plant again. Baptisia australis will grow well in regular garden soil as well as your rain garden soil mix and this little one could be transplanted to another area of the yard in fall.

The Functioning Rain garden

Thirty six straight hours of rain gave us 2.9 inches of rainfall a few days ago. After filling the 4 rain barrels (260 gallons), an additional 1500 gallons were filtered through the rain garden and returned to the water table. The standing water only lasted an hour or two before it had all been absorbed.

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.

Value of rain gardens recognized

You probably noticed my mentioning The King's Daughters Inn rain garden in an earlier post. I am pleased to say that they have recently received both an environmental award from the Durham County Soil and Water District as well as a Sustainable Properties award from the Durham City/County Appearance Commission. The King's Daughters Inn is a 17 room bed & breakfast newly opened in a restored building built in 1925. Part of the restorations included incorporating as many 'green practices' as possible in the restoration. An underground cistern, grey water system, 'smart' thermostats and the large rain garden that comprises half of their front landscape all helped to bring them these honors.

As water quality issues become serious concerns for many municipalities, the humble little rain garden suddenly is being recognized as one of the solutions. And the beauty of this solution is that anyone can help improve water quality and prevent storm water runoff by installing a raingarden in their yard.