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Colorado’s water supply is under threat from climate change and population growth. Limiting outdoor use is an increasingly popular approach to conserving water, yet to implement effective conservation policies, utilities managers need a better understanding of local outdoor water consumption.
That’s what led Colorado State University’s Melissa McHale, an associate professor in the Department of Ecosystem Science and Sustainability, to explore what drives outdoor water consumption in an area projected to undergo significant population growth in the years to come.
McHale teamed up with scientists from the U.S. Forest Service and Denver Urban Field Station – a research and practice unit of the USDA Forest Service Rocky Mountain Research Station – and a water conservation specialist from Fort Collins Utilities.
The team’s study, “When Small Is Not Beautiful: The Unexpected Impacts of Trees and Parcel Size on Metered Water-Use in a Semi-Arid City,” was recently published in Remote Sensing.
More trees can help conservation efforts
Among the findings, McHale said trees can provide long-term benefits even if they need to be watered directly when they are first planted.
“Other modeling analyses have highlighted the benefits of tree shade,” she said. “But very rarely do we have real data that help us specifically create management decisions and policies that support the world we live in, and the balance we need to achieve.”
The research team found that residential properties with a higher ratio of vegetation cover to lot size tended toward less water consumption. McHale said that discovery was surprising.
“In semi-arid cities, tree cover is directly linked to land surface temperature,” she explained. “It’s a real positive result for us along the Front Range, because mature tree canopy may mean that people use less water outdoors.”
McHale said it would be ideal if people could use less water while also cooling the landscape with tree cover.
“But I’m not sure so far, the way we’re developing the land, if we’re providing opportunities in the best way we can,” she said.
Wealthier households and properties with small lots use more water outside, according to the study. These conditions are prevalent in current development patterns along the Front Range in Colorado.
“We need to make sure we provide enough space, in the right locations, for mature tree canopy to grow in these new developments,” McHale said.
Additional research from other semi-arid cities, like Salt Lake City, has shown that planting non-native trees may be better for reducing water consumption in such areas.
Local policies may hinder conservation efforts
McHale also said that subdivision homeowner associations may be setting and enforcing guidelines that encourage more outdoor water use. Most newer neighborhoods with houses built in close proximity to each other are governed by HOAs, and the research team wants to delve deeper into this question in future research.
Shaunie Rasmussen, research associate in the CSU Department of Ecosystem Science and Sustainability and a co-author on the study, said with urbanization taking place so quickly, it’s imperative to get trees planted, to make sure they’re mature as people move into new houses along the Front Range.
“It’s important to establish this tree cover and to take advantage of the benefits of trees,” she said. “Based on our research, trees can be a water-saving resource.”
Rasmussen graduated from CSU in July 2020 with a master’s degree in ecosystem sustainability, a recently established program through the Warner College of Natural Resources, and is now based at the Denver Urban Field Station.
McHale said this research project aims to strengthen and expand upon the university’s land-grant mission.
“We’ve been really trying, as a university, to reinvent the way we engage with our communities,” she explained.
Teaming up with the U.S. Forest Service, which has played a central role in pushing the field of urban ecology nationally, was a natural fit. The City of Fort Collins has already made use of the research findings from other collaborative research projects with McHale’s lab, and included those results in planning documents and budget requests for city managers.
“That’s the essence of engaged research,” said McHale. “You learn something different by working together and the outcomes are more impactful. We’re all in this together.”
McHale was recently selected to be a member of Denver’s Sustainability Advisory Council, which was originally created in 2010 by Mayor John Hickenlooper, and continues today under Mayor Michael Hancock.