NOLA Rain Gardens Monitoring
by Zachary Batterman
I have been monitoring and observing two rain garden sites in New Orleans since December 2014. One site is located at 8641 Forshey St in Hollygrove, the other is located at 5301 Wildair Dr in Filmore. The first thing I noticed about these two sites is that although they are only located several miles away from each other, they both respond differently during rain events. I have observed that the Wildair rain garden generally accumulates more water during and after a rain event. This could be because the site receives more rain during events or has poor drainage compared to the Forshey site. I have been able to collect a water sample from the retention cell at Wildair up to 48 hours after a large rain event, whereas the Forshey site will be dry after the same amount of time. I believe this must be associated with the amount of rain each site receives because other factors such as erosion, vegetation coverage, condition of plants and the amount of unwanted vegetation have been very similar at each site over time.
As far as analyzing the water quality indicators, both sites have had very similar results. I have been testing dissolved oxygen (DO), temperature, nitrate-nitrogen, phosphorus, bacteria (fecal coliform), chlorine, copper, hardness, iron, and Ph. Both sites have tested consistently similar for the following; DO: 4-8ppm. Temperature: Varies per visit but has not seemed to impact other indicators significantly. Nitrate-nitrogen: 0-5ppm. Phosphorus: 1ppm. Bacteria (Fecal Coliform): Positive. Chlorine: 0ppm. Hardness: 40-120. Iron: 0ppm. Ph: 7 or 8. While these sites are located several miles apart, they are both located in residential neighborhoods and most likely have the same inputs of chemicals and bacteria, resulting in similar water quality results.
The rain garden project is working in partner with the Mosquito&Termite control board to monitor if these sites are creating ideal breeding grounds for termites and mosquito’s. Since I have been monitoring these sites from December through April I have not seen much activity because we have been in the winter months. However, in my most recent monitoring I have noticed an increase in insect activity. My only concern here would be the standing water (specifically at the Wildair site) after rain events. Standing water is a prime environmental condition for mosquito breeding. However the standing period may not be long enough to produce good conditions for breeding. From my observations so far I have been impressed with the rain gardens here in New Orleans. I think they are proving to be a good way to relieve drainage problems in the area and are given us valuable information into what the quality of the drainage water is in these neighborhoods.
Hopefully through the combined effort of Water Works, Bayou Land RC&D, and the Mosquito&Termite Control board we can continue to monitor these gardens long into the future and provide valuable data to help improve the communities we live in.