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##   USGS EROS Helps Assess OpenET Accuracy

### OpenET found to work especially well in cropland and water-scarce areas

      By Earth Resources Observation and Science (EROS) Center       February 20, 2024    

A new study addresses a question that resource managers have been wondering: Just how accurate is OpenET? The online mapping tool, based on Landsat and other satellite data, helps track and manage water use such as irrigation in the western United States.

The tool is pretty accurate, as it turns out—especially for annual crops and in arid areas where the demand for water can exceed the supply and sustainable water management is crucial.

OpenET was developed by a broad team of federal agency, university and other collaborators, including several USGS Earth Resources Observation and Science (EROS) Center scientists. They contributed an EROS evapotranspiration (ET) model, SSEBop, for the OpenET ensemble of six models that generally represents the average. ET is the amount of water lost to the atmosphere through soil evaporation and plant transpiration and can be estimated by ground-based methods in specific spots or by using satellite data over broad areas, as the OpenET models do. 

Recently released in Nature Water, the study compared OpenET data with data from 152 point-based flux tower stations that provide reliable estimates for ET in a variety of landscapes. The study found “high accuracy” of OpenET use for cropland, according to the article.

View Media Details

USGS EROS Research Physical Scientist Gabriel Senay created the SSEBop model, helped develop OpenET and helped design and co-author the comparison study. EROS contractors Mac Friedrichs and Gabriel Parrish were also a part of developing OpenET and co-authors of the study. “The study results strengthen and justify the continued use of remote sensing techniques for estimating evapotranspiration and its application for agricultural water management,” Senay said.

Study co-author Justin Huntington, a research professor at the Desert Research Institute (DRI), reinforced that sentiment. “Evapotranspiration is one of the hardest hydrologic fluxes to measure, and to think we are estimating this flux from space with comparable or better accuracy to ground-based weather stations and meter data for agricultural lands is really remarkable,” he said in a DRI news release. 

“The combined use of the Landsat satellite archive with new Google Earth Engine cloud computing resources has been key, as has our collaboration across different research groups and use of multiple models to better understand model strength and weaknesses and identify areas for improvement,” Huntington added.

### **Accuracy and Usage Examples of OpenET**

For annual crops, the study found that the OpenET average error rate fell within the targeted range set by partners such as farmers and water management agencies. And for crops growing in Mediterranean and desert climates such as California and portions of the Southwest, certain error rates were even lower. Accuracy in natural landscapes such as forests and wetlands varied.

OpenET is intended to provide easy access to information at a field scale to help land and water managers monitor water usage and make informed decisions. The ensemble aims for estimates that are at least as accurate, if not more accurate, than an individual ET model. In addition to the ensemble model, the study also compared individual model data to ground-based data.

“One of the main strengths of this study is to reinforce the fact that remote sensing ET is relatively accurate and consistent across models, indicating the maturity of the models, particularly over croplands. Water managers can effectively use either the ensemble or any of the models to quantify field-scale crop water use over large areas and time periods to understand and characterize water use trends and water budgets,” Senay said. The archive of Landsat thermal data, publicly available through EROS, allows for ET comparisons spanning four decades.

OpenET has been used for a variety of purposes since launching in 2021. For example, OpenET helps Sacramento-San Joaquin Delta farmers comply with California law to measure and report accurate water use. In Diamond Valley, Nevada, OpenET helps hay farmers understand the historical and current implications of irrigation as groundwater levels decline. And OpenET helps an Arizona water and power utility understand how forest restoration activities are changing water balances in the Salt and Verde River watersheds.  

An OpenET conference in late February 2024 will bring together OpenET users to highlight and provide feedback on ways OpenET has been used and encourage collaboration. Senay, Friedrichs and Parrish from EROS will attend, with Senay giving a presentation.   

## Related Content

                -              Multimedia           
                -              News           

Listen to Eyes on Earth podcast episodes to learn more about OpenET and evapotranspiration.

October 5, 2020

####   Eyes on Earth Episode 35 – Watching the Water Supply with OpenET

Evapotranspiration is the process by which water transpires from the leaves and stems of plants and evaporates from the Earth’s surface. ET is an important metric for managing water use, but data availability has long been an issue.

Core Science Systems Mission Area, National Land Imaging Program, Earth Resources Observation and Science (EROS) Center 

Eyes on Earth - Gabriel Senay

Eyes on Earth Episode 17 - Evapotranspiration

Eyes on Earth - Gabriel SenayEyes on Earth - Gabriel Senay

February 24, 2020

#### Eyes on Earth Episode 17 - Evapotranspiration

link

It’s easy enough to measure rainfall, and nearly as easy to measure streamflow. Calculating the efficiency of water use through the metric of evapotranspiration (ET) – evaporation off the Earth’s surface and transpiration from the leaves of plants – is a far trickier proposal.

Earth Resources Observation and Science (EROS) Center , Landsat Missions

Eyes on Earth - Gabriel SenayEyes on Earth - Gabriel Senay

February 24, 2020

#### Eyes on Earth Episode 17 - Evapotranspiration

link

#### Eyes on Earth Episode 17 - Evapotranspiration

link

It’s easy enough to measure rainfall, and nearly as easy to measure streamflow. Calculating the efficiency of water use through the metric of evapotranspiration (ET) – evaporation off the Earth’s surface and transpiration from the leaves of plants – is a far trickier proposal.

Earth Resources Observation and Science (EROS) Center , Landsat Missions

link

October 21, 2021

####                 OpenET Launch Gives EROS Scientists—and Water Managers—Reason to Celebrate              

The Landsat 9 satellite’s launch September 27 will ensure the continuity of thermal imaging for the work of the evapotranspiration (ET) team at the USGS Earth Resources Observation and Science (EROS) Center.

Core Science Systems Mission Area, Earth Resources Observation and Science (EROS) Center , Landsat Legacy

EROS Scientists Publish Accuracy, Guidance for Global Evapotranspiration Data

May 12, 2020

####   EROS Scientists Publish Accuracy, Guidance for Global Evapotranspiration Data

Evapotranspiration (ET) presents a difficult problem.

Evaporation from the Earth’s surface and transpiration from the leaves of plants accounts for...

Read Article

EROS Evapotranspiration Model Key Part of Upper Rio Grande Basin Study

June 27, 2018

####   EROS Evapotranspiration Model Key Part of Upper Rio Grande Basin Study

Kyle Douglas-Mankin wants to know where the raindrops go when they fall on the arid and semi-arid landscapes of the Upper Rio Grande Basin.

Read Article

## Related Content

Listen to Eyes on Earth podcast episodes to learn more about OpenET and evapotranspiration.

October 5, 2020

####   Eyes on Earth Episode 35 – Watching the Water Supply with OpenET

Evapotranspiration is the process by which water transpires from the leaves and stems of plants and evaporates from the Earth’s surface. ET is an important metric for managing water use, but data availability has long been an issue.

Core Science Systems Mission Area, National Land Imaging Program, Earth Resources Observation and Science (EROS) Center 

Eyes on Earth - Gabriel Senay

Eyes on Earth Episode 17 - Evapotranspiration

Eyes on Earth - Gabriel SenayEyes on Earth - Gabriel Senay

February 24, 2020

#### Eyes on Earth Episode 17 - Evapotranspiration

link

It’s easy enough to measure rainfall, and nearly as easy to measure streamflow. Calculating the efficiency of water use through the metric of evapotranspiration (ET) – evaporation off the Earth’s surface and transpiration from the leaves of plants – is a far trickier proposal.

Earth Resources Observation and Science (EROS) Center , Landsat Missions

Eyes on Earth - Gabriel SenayEyes on Earth - Gabriel Senay

February 24, 2020

#### Eyes on Earth Episode 17 - Evapotranspiration

link

#### Eyes on Earth Episode 17 - Evapotranspiration

link

It’s easy enough to measure rainfall, and nearly as easy to measure streamflow. Calculating the efficiency of water use through the metric of evapotranspiration (ET) – evaporation off the Earth’s surface and transpiration from the leaves of plants – is a far trickier proposal.

Earth Resources Observation and Science (EROS) Center , Landsat Missions

link

October 21, 2021

####                 OpenET Launch Gives EROS Scientists—and Water Managers—Reason to Celebrate              

The Landsat 9 satellite’s launch September 27 will ensure the continuity of thermal imaging for the work of the evapotranspiration (ET) team at the USGS Earth Resources Observation and Science (EROS) Center.

Core Science Systems Mission Area, Earth Resources Observation and Science (EROS) Center , Landsat Legacy

EROS Scientists Publish Accuracy, Guidance for Global Evapotranspiration Data

May 12, 2020

####   EROS Scientists Publish Accuracy, Guidance for Global Evapotranspiration Data

Evapotranspiration (ET) presents a difficult problem.

Evaporation from the Earth’s surface and transpiration from the leaves of plants accounts for...

Read Article

EROS Evapotranspiration Model Key Part of Upper Rio Grande Basin Study

June 27, 2018

####   EROS Evapotranspiration Model Key Part of Upper Rio Grande Basin Study

Kyle Douglas-Mankin wants to know where the raindrops go when they fall on the arid and semi-arid landscapes of the Upper Rio Grande Basin.

Read Article

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