Measuring water from the sky
And the start of a new water year.
Hey there, and welcome back to Western Water Notes.
I mostly focus on regional issues here in the American West, but I’m starting out this edition with a note about Hurricane Helene: The videos and images coming out of the Southeast this week are crushing and heartbreaking to watch. In a matter of just days, enough water fell (40 trillion gallons) to fill up Lake Tahoe or 60 million Olympic-sized swimming pools, according to the Associated Press. Recovery will take years, and I wanted first to share some resources:
Ways to donate and help flood victims (Blue Ridge Public Radio)
Along with Blue Ridge Public Radio, news coverage from the Citizen-Times.
Finally, zooming out, Weather West’s Daniel Swain had a thoughtful, worthwhile thread about planning for the “worst-case scenario” in emergency management.
Today, I’m focusing on a topic I’ve wanted to write about for months: How a new satellite-driven data tool is helping us learn a lot about water use in the West, with applicability in many other places. The most important tool you’ve never heard of? I’ll let you decide that.
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This is a story about water on Earth that starts in space.
Look up at the night sky, and you might spot a satellite lighting the edges of darkness. They are used for all sorts of applications — communication, navigation and research.
But several are used to better understand Earth, and our human relationship to it. At ~400 miles above Earth, orbiting our planet 14 times a day, satellites like Landsat can even help answer questions about water use in places where there is not much data.
And a new(ish) online platform makes it easy to view the data, closing an important gap for water data that is otherwise inaccessible or cost-prohibitive for many. Built with Google Climate Engine as part of a project led by NASA, the Desert Research Institute and Environmental Defense Fund, OpenET launched its platform in 2021.
I have to admit, when I first heard (and wrote) about it, it was a little hard for me to wrap my head around the details. The OpenET platform relies on a large technical framework: satellite data, multiple models and hydrologic science. Once I dug a little more though, I started to see the application and value of having this data be so open and available to the public. In many ways, it democratizes a key piece of water data.
Wait, how can satellite data help us understand water use? My first question too.
It’s all in the name. ET stands for “evapotranspiration,” what might well be the most important word few people have never heard of as we grapple with a changing, drying regional climate. Evapotranspiration describes how water moves from land surface to the atmosphere through evaporation from soils and transpiration from vegetation.
On crop fields or even lawns in cities, evapotranspiration provides a measure of how much water is being used (i.e. consumed) by vegetation. That’s why it offers a key data point in understanding water use in regions like the West. And it fills a critical gap because getting this data can be a) costly, b) inaccessible and c) meters do not always provide field-level measurements. The lack of data leaves many people in the dark, from regulators and water managers to irrigators and communities. Not to mention the public, from journalists and researchers to activists and advocacy organizations.
There are all sorts of ways understanding ET from the sky can help us explore and better understand our relationship to water in the West. Researchers can apply ET to monitor and observe ecosystems, wetlands and groundwater-dependent vegetation.
And the amount of water our ecosystems breathe out through evapotranspiration is a critical (if often invisible and unaccounted) part of the water cycle — one that is not always considered in how water is managed. For example, a March paper about the Colorado River found that roughly one-fifth (19%) of the river’s water cycles through riparian and wetland vegetation, a determination made by looking at OpenET.
It’s pretty neat stuff. And worth playing around with the site.
I’m writing about it now because I talked a couple weeks ago with Thomas Ott and Sayantan Majumdar with the Desert Research Institute about a new paper they co-authored looking at how OpenET’s estimates compared to data from field meters at field in two Nevada and Oregon valleys where groundwater aquifers are overused.
And they found that OpenET can help with groundwater management.
The press release sums up their conclusions well:
“The results demonstrate that OpenET can be used to accurately estimate the amount of groundwater used for crop irrigation at the level of individual fields. This is the first research to follow water from a groundwater well to a single field of crops, assess how much of that water the crops consumed, and provide insights into irrigation efficiencies at the same time. The method can inform water use for groundwater management planning across the country.
Researchers plan to use OpenET in the Nevada Water Initiative, an effort to update the state’s knowledge of groundwater. Nevada currently relies on groundwater basin assessments made ~50 to 70 years ago with less precise tools. “We have more capable methods to assess actual water use, and that's what OpenET is looking to do,” Ott said.
One last paper: The OpenET team published in Nature Water this January showing a strong accuracy between OpenET data and field measurements in agricultural areas.
There’s lots to write about here, and I hope to dive into more OpenET use cases and field applications this year. Again, it’s worth spending some time with the data.
One last thing:
Oct. 1 (yesterday) was the start of the new water year. Here’s to all who celebrate!
We’ll watch what it brings…
Until next time,
Daniel
Great content, Daniel. This journalism is excellent and cruical - please keep it up!