Too precious to use once

New Mexico is facing a new weather normal – longer drought punctuated by briefer, stronger storms – but communities are responding with a low-tech solution: green stormwater infrastructure. These projects help mitigate flooding, capture precious water, irrigate urban trees and filter runoff before it returns to aquifers and waterways. With drought predicted to persist, capturing every drop of precipitation – no matter how fast or furious it comes – could make the difference in keeping communities livable. 

The heralding of a  super El Niño  this summer excited many New Mexicans for the prospect of an abundantly rainy monsoon. Amid historic megadrought, and on the heels of the  lowest snowpack on record , this forecast rolled in much like an afternoon storm: a welcome relief.

But in Ruidoso or Las Vegas, where catastrophic wildfire has altered landscapes, a super monsoon brings a different mood. Even in a standard one-tenth inch rain event, hydrophobic burned soils repel water. Summer rains can quickly become a second wave of disaster. Even outside burned areas, New Mexico’s cities still see dangerous floods, like those that hit in  Zuni Pueblo  last month.

One low-tech tool is helping cities adapt: Green stormwater infrastructure is beginning to hit its stride in New Mexico.

In June, the City of Albuquerque, the state’s stormwater leader, approved an  ordinance  to permanently fund green stormwater infrastructure across the city. The City of Santa Fe recently updated their five-year stormwater management plan. In Las Vegas, green stormwater infrastructure will help mitigate flooding from the Hermit’s Peak-Calf Canyon Fire and  harness floodwater to grow the city’s urban forest .

“The stars are sort of aligning, and there’s this new breadth of interest in green stormwater infrastructure,” said Zoe Isaacson, river and watershed manager for the City of Santa Fe. “People are beginning to realize that green stormwater infrastructure offers a multi-beneficial approach to addressing climate change.”

Ranging from regional flood control projects to humble curb cuts and rain gardens, green stormwater infrastructure is a versatile umbrella for a wide suite of water retention and treatment methods. These projects divert and capture rainfall in permeable basins made to mimic natural depressions. Moisture seeps slowly into the soil; plants and soil filter pollutants while runoff waters greenery and recharges shallow aquifers or returns to rivers.

These seemingly small changes reconnect key links in the water cycle that urban development has historically disrupted. Moreover, they respond to a problem arid communities face across the Southwest: too much water arriving too quickly.

“This whole concept is to not only hold water where it falls, but to then use it to build shaded oases and wildlife habitat, recharge our water systems, cool the spaces people use and increase our quality of life,” said Sarah Hurteau, resilient cities program director for SIG-NAL, the nonprofit that helped develop Albuquerque’s recent ordinance.

As New Mexico’s climate changes, this green tech can help cities adapt to new weather patterns: longer dry spells punctuated by briefer, stronger storms.

“We need to be able to capture the water that comes in these quick thunderstorms that bring a lot of water all at once, rather than the slow-moving monsoons we used to have where water could slowly penetrate into the ground,” said Kristen Sanders, Las Vegas urban and community forester with the Forestry Division. “In the Southwest, green stormwater infrastructure is the solution to keeping our urban forest alive.”

By harnessing the built environment, water managers can conserve every drop during peak pulse moments. With as little as one-tenth of rainfall – a standard storm in New Mexico – Las Vegas’ impervious surfaces like roads and buildings could harness  up to 3.23 million gallons of water,  according to the city’s new Urban Forestry Management Plan.

By capturing water and irrigating trees, these urban projects usher in a host of “co-benefits,” such as cooling shade, habitat for wildlife and better access to nature in cities, which is linked to better health, mental and socioeconomic outcomes.

In Las Vegas, this green tech is addressing both post-fire recovery and climate adaptation.  Even before post-fire floods, the city’s trees were aging out. Las Vegas needed a plan to retain its characteristic urban forest into the future. But now, green stormwater infrastructure is a critical post-fire restoration tool to assuage the worst of floods and reduce strain on the municipal water system – while supporting a new generation of trees in the arid city.

“A colleague of mine once said, ‘Water in the desert is too precious to use once,’” Hurteau recalled. “But what we were doing: changing the paradigm from seeing water as a liability and removing it as fast as we could out of the streets and into the river, and with it, tons of pollution, to viewing stormwater as a resource to increase climate resilience and water conservation.”

All these pollutants can stress water treatment centers or otherwise flow untreated through arroyos and waterways into rivers.

Albuquerque and Santa Fe are permitted by the EPA to discharge stormwater before it returns to the Rio Grande. Downstream users along the state’s mainstem river rely on decisions made upstream. Riparian ecosystems also depend on water managers’ decisions. This is critical in Santa Fe, one of few communities in the world that recognizes  their river’s right to water. 

“We’re very focused on improving water quality,” Isaacson said, “but we’re definitely trying to stack all these benefits green stormwater infrastructure provides.”

By capturing water and irrigating trees, these urban projects usher in a host of “co-benefits,” such as cooling shade, habitat for wildlife and better access to nature in cities, which is linked to better health, mental and socioeconomic outcomes.

The pre-planning and design that goes into green stormwater infrastructure decentralizes water treatment and relies on the most low-tech filtering method: nature.

“Trees are the filtration system,” Sanders said. “We choose trees specifically tolerant to tough conditions, ranging from pollutants to salts from de-icing the roads in the winter.”

Pollutants aren’t the only factor in selecting urban trees. Urban foresters like Sanders must increasingly account for an unstable climate. These days, it’s not uncommon for a 75-degree day to snap into a 15-degree polar vortex night, as Sanders recalled from her time working in Denver. These swings  stress trees out  by confusing internal dormancy triggers, causing premature bud bursts, and increasing vulnerability to frost damage.

“Our established forests are really going to struggle with these wild temperature variants,” Sanders said. “Yes, it’s warming, but you’re still going to get those hard freezes and those crazy snowstorms – so how do you account for that?”

New Mexico’s  plant hardiness zones  are  predicted to inch northward : Albuquerque’s vegetation will come to resemble that of Las Cruces, and Las Cruces will become more akin to Tucson. In Las Vegas, the climate is anticipated to shift classification from  a 6a to a 7a or even an 8a  – causing it to resemble the current climate of Truth or Consequences.

 Climate-ready trees  – trees that can withstand both current conditions and anticipated climate changes – dovetail with green stormwater infrastructure.

Sanders and Hurteau work as members of the New Mexico Tree Alliance to develop the list of trees suited to the task. Some promising frontrunners include Osage orange, Kentucky coffee and, of course, junipers. Different elm varieties – beyond the notoriously invasive Siberian elm – also show promise.

“I know everyone isn’t a huge fan, but elms are tough as nails,” Sanders said.

With drought predicted to persist in the Southwest, capturing every drop of precipitation – no matter how fast or furious it comes – could make the difference in keeping communities comfortable and livable.

“In Albuquerque, there isn’t a tree that doesn’t need irrigation,” Hurteau said. “GSI provides supplemental irrigation without drawing on potable water.

“But we have to put the right tree in right place and under the right conditions,” Hurteau continued. “No amount of green stormwater infrastructure will help the wrong tree survive the heat.”

But these interdependent methods may help communities thread the needle of climate adaptation.

“We’re working diligently to find solutions,” Sanders said. “The two solutions are green stormwater infrastructure and choosing the right tree.”