Way back in January, I talked about the treatment wetlands that San Dieguito River Park put in to capture and clean the storm water runoff before it enters the San Dieguito Lagoon. We have some more data to share with you, now that the wetlands have matured a bit.
Fecal Indicator Bacteria: Affecting your surf days
Once the wetlands somewhat established themselves, the wetlands dropped the concentrations of fecal indicator. Fecal indicator bacteria coming from urban runoff from the storm drain system is the reason why our beaches are closed or under advisories for most of the winter. If we can clean the water before it gets to the ocean, it means more safe winter surfing days.
Nutrients and Oxygen: Affecting the health of the lagoon
As you can see by the graphs showing nitrate and ammonia, the treatment wetlands continue to do an amazing job filtering out nitrogen based nutrients. 100% of the samples from the storm drain pipe have ammonia values well above the basin plan standards. In contrast, all of the water coming out of the treatment ponds has ammonia concentrations below the water quality standards. In a process known as eutrophication, high levels of nutrients cause algal blooms which can choke up the natural flow of the lagoon and cause a shift in plant communities that habitat the lagoon.
The treatment ponds also raise the levels of dissolved oxygen of the water entering the lagoon. Low levels of oxygen in the water will stress the fish and invertebrates that live in the lagoon, potentially causing them to suffocate.
All in all, it looks like the treatment wetlands that San Dieguito River Park installed work really, really well. Read more about the awesome work San Dieguito River Park does. I recoment going to the park and hiking the trails, they really are quite beautiful. For those of us who like to get our hands dirty, they have a lot of hands-on volunteer opportunities doing things like trail and habitat restoration. You can check out the rest of the San Dieguito River Park on our watersheds Wiki (the sites are SGT-040 and SGT-050). While you’re at the wiki, check out the water quality monitoring results at the other sampling locations we have throughout San Diego.