Study to measure rain garden water quality impacts

Gardens provide many benefits to both owners and communities: cleaner air, increased wildlife and produce, if food is planted.

But what about rain gardens? Rain gardens are generally landscape areas that collect water and have a lower elevation than the surrounding area. Berms are part of the rain garden design and are earthen walls usually up to a foot tall that surround the lower part of the garden and help keep water in it.

“The composition of a rain garden is a little different from a regular garden in the sense that we need to make sure the infiltration to the bottom layers of soil and plants capture the nutrients from rainwater runoff and that there is enough time for that to happen,” said Bardia Heidari, Ph.D., Texas Water Resources Institute (TWRI) research scientist.

Rain gardens are part of green infrastructure, which includes measures that can be used in urban and suburban environments to help manage stormwater, reduce heat, improve air quality and more. Rain gardens in particular, Heidari explains, improve stormwater quality and quantity.

Headquartered at the Texas A&M AgriLife Research and Extension Center in Dallas, Heidari and his collaborators have created two rain gardens at two community gardens in the Dallas area. They will study the water quality at both sites and will use a third community garden without a rain garden as a control site.

“We want to see what the concentration of pollutants and nutrients coming out of the community gardens is and then make a comparative analysis to see, with these implementations, how much of the load from pollutants and nutrients we can expect to be reduced,” Heidari said.

This project idea formed around the idea of best management practices for community gardens, he said, but the team decided to experiment with structural best management practices, focusing on green infrastructure and rain gardens.

“We wanted to see, if we don’t apply these techniques, what the water quality from these community gardens is, and then assess the level of stormwater quality improvement using such rain gardens,” Heidari said.

The plants chosen for the garden are native to Texas, said Dean Minchillo, a program specialist at TWRI.

“The choice of plants was decided based on plants that could handle extreme fluctuations and weather,” Minchillo explains. “A rain garden should exist on its own without any extra inputs other than what nature provides.”

Green infrastructure successfully impacting the environment requires widespread implementation, Heidari said. To see improvements in water quality and ecosystem health, these practices need to be widely adopted.

“We are hoping that by executing these demonstration projects, for the long term, we have a portfolio of success stories that we can present to a wide range of stakeholders,” Heidari said.

Public education is key to this project for Heidari. The team is working to help residents understand how their actions can affect not just themselves, but their watershed and community.

“The watershed needs to be taken care of as a whole unit,” Heidari said. “It’s something that everyone is contributing to, and to allow the watershed to survive through generations, we need to understand that we have to invest in a way that allows environmental sustainability. These practices are one solution towards that bigger goal.”