Urban watershed study proposes new concepts of urban ecosystems

A study co-authored by Dr. Sujay Kaushal, assistant professor at ESSIC and the Department of Geology at the University of Maryland, and hydrologist Ken Belt proposes an expanded view on urban watersheds.

The study, entitled “The urban watershed continuum: evolving spatial and temporal dimensions,” mainly considers a new part of urban ecosystems, infrastructure. With watersheds expanding and cities and urban environments changing over time, the study presents a new concept for the effects of urban areas on urban ecosystems.

“There’s studies of urban infrastructure – such as storm drains – but [storm drains aren’t] really considered as part of the ecosystems. So there are these emerging ecosystems all around us and this paper basically incorporates infrastructure as part of ecosystems,” Kaushal said.

Human-made headwaters – like storm pipes for example – are all around us, and because there’s so many of them now, they need to be a part of watersheds,” Kaushal said.

The framework used to address characteristics of watersheds is four-dimensional eco-hydrologic entities across space and time, according to Kaushal. The entities, vertical, longitudinal, lateral, and temporal, were used to better understand the inner-workings of the complicated underground system that has vast implications for above-ground stream ecosystems, along with the people who depend on them, according to the study.

Based off of different management activities or restoration sources, he said, stream systems change over time and present different trajectories.

Kaushal said, with over half of the world’s population living in urban areas, people depend on streams and rivers on a daily basis, and as a result, there are plenty of practical applications that rely on urban water ecosystems.

“By thinking about how watersheds are put together, we can get a better handle on transportation, on pollutants and how to manage [watersheds] better and have more effective water restoration strategies,” he said.

He said he and co-author Ken Belt of the Forest Service’s Northern Research Station developed the study from various observations made while working with urban streams.

“It was a good partnership because Ken’s training is in engineering and I’m in the geosciences so it worked out nice,” Kaushal said. “After working on different projects over time, we wanted to come up with a concept about how watersheds expanded, so that kind of led to this concept paper.”

He said a focus of the study was to vastly expand the view and role of stream networks in watersheds.

“Just from looking around, we saw gutters and storm drains and all of this infrastructure all around us and we basically realized how it is all connected to streams,” Kaushal said.

A way the study can be applied, he said, would be to incorporate human-made structures into the concept of what a watershed is in order to better understand where pollutants come from. This improved understanding could also open up the door to target restoration activities in urban areas.

Kaushal said actions taken today may affect how ecosystems will function over time, and what transpires from these actions will affect future generations in terms of water resources.

But looking into the near future, he said the next steps will be to test out the study’s concept and developing management applications in cities like Baltimore.