Building Basins and Filling Them—With Water, Plants, and Birds!

By Kari Hackney

 
After a complete bust of a monsoon season in 2020, I held my breath in anticipation of what summer 2021 would bring. Rainwater harvesting is a key component in many of our restoration projects. Digging in Tucson can require some serious muscle, so these rainwater basins are a labor of love and the results are well worth it. While many desert plants are known to be a bit slow growing, if planted in a basin they become established fairly quickly. As this year’s monsoon season approached, I hoped for anything but a repeat of last year. Luckily, Tucson’s 2021 monsoon ended as the 3rd wettest on record. The plants, and all those who dug those caliche-lined basins, gave a sigh of relief as our basins filled with water and demonstrated the benefits of creating systems that work with nature rather than against.

After: The new Hacienda del Rio basins performed perfectly during a 1.5" rain event.

One of the greatest examples of these systems is green stormwater infrastructure (GSI). GSI often takes the form of constructed features that capture stormwater runoff from paved areas, using vegetation to help rainwater infiltration. GSI provides an incredible opportunity to create sustainable urban habitat while also addressing some of Tucson’s greatest environmental vulnerabilities. Re-envisioning stormwater as an asset that can be managed through GSI increases ground water recharge, supports native vegetation that provides habitat and cools public areas, filters pollutants, and reduces flooding.

For Tucson Audubon, GSI presents an opportunity to create urban habitat that replicates one of the region’s most productive habitats: desert washes. Tucson Audubon restoration crews have installed multiple GSI projects around Tucson that were put to the test during the 2021 monsoon season. A great example of these structures can be found right outside our Nature Shop at University & 5th Ave.

Basins outside of the Historic Y

Installing new GSI or repairing poorly implemented stormwater infrastructure is a win-win for people and wildlife. Our most recent GSI project at the Hacienda del Rio neighborhood began with removing the riprap-filled channel that is common in non-functioning landscape designs. Many existing stormwater structures lack the most essential component for them to function: plants! Plants are necessary to draw water down into the soil, improving infiltration. Without plants, the result is water standing for days on end, becoming breeding grounds for mosquitos. Excavating basins of varying sizes and depths allowed us to manipulate how water flowed throughout the area, while also allowing us to include a healthy variety of native plants found in a variety of environments. We planted our deepest basins with xeroriparian (infrequently flowing waterways or washes) vegetation, but the berms and shallower basins allowed us to include a broader suite of plants found in other habitats. Native trees such as velvet mesquite (Prosopis velutina) and netleaf hackberry (Celtis reticulata) significantly improved the habitat value while also providing shade for the residents. A year and one lovely monsoon season later, the habitat was thriving and the residents (I guess you could count the people too!) couldn’t be happier.

Before: Removing non-functioning riprap

Before: Potential erosion hazard and water has a speedy exit and no habitat.

Operating an excavator was a bonus, one that made me grateful I had spent countless hours in “training” as a kid on a toy excavator in my sandbox.

After: The new Hacienda del Rio basins performed perfectly during a 1.5" rain event.

Homeowners and HOAs are able to include GSI on their properties and in their neighborhoods at any scale. Tucson Audubon offers restoration services that include consults and installations. Contact Kari Hackney (khackney@tucsonaudubon.org) if you’re interested in any of our services or have questions. We’d love to help you create sustainable urban habitat that benefits people and birds.

Kari Hackney is the Urban Habitat Restoration Manager at Tucson Audubon.