OpenET: Filling the biggest data gap in water management for the Western United States

Authors: MELTON, F. - California State University; HUNTINGTON, J. - Desert Research Institute; GRIMM, R. - Environmental Defense; HERRING, J. - Habitat Seven; HALL, M. - Environmental Defense; ROLLISON, D. - Environmental Defense; ALLEN, R. - University Of Idaho; Anderson, Martha; BLANKENAU, P. - Idaho Department Of Water Resources; BROMLEY, M. - Desert Research Institute; DAUDERT, B. - Desert Research Institute; DOHERTY, C. - Stanford University; DUNKERLY, C. - Desert Research Institute; FISHER, J. - National Aeronautics And Space Administration (NASA); FRIEDRICHS, M. - Us Geological Survey (USGS); GUZMAN, A. - California State University; HAIN, C. - Nasa Marshall Space Flight Center; HALVERSON, G. - National Aeronautics And Space Administration (NASA); HANSEN, J. - Desert Research Institute; HARDING, J. - Habitat Seven; JOHNSON, L. - California State University; KANG, Y. - University Of Wisconsin; KILIC, A. - University Of Nebraska; MINOR, B. - Desert Research Institute; MORTON, C. - California State University; ORTEGA-SALAZAR, S. - University Of Nebraska; OTT, T. - Desert Research Institute; OZDOGAN, M. - University Of Wisconsin; REVELLE, P. - University Of Nebraska; RUHOFF, A. - Universidade Federal Do Rio Grande Do Norte; SCHULL, M. - University Of Maryland; SENAY, G. - Us Geological Survey (USGS); VOLK, J. - Desert Research Institute; WANG, C. - California State University; YANG, Y. - University Of Maryland; Anderson, Raymond - Ray

Submitted to: Journal of the American Water Resources Association
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/4/2021
Publication Date: 11/2/2021
Citation: Melton, F., Huntington, J., Grimm, R., Herring, J., Hall, M., Rollison, D., Allen, R.G., Anderson, M.C., Blankenau, P., Bromley, M., Daudert, B., Doherty, C., Dunkerly, C., Fisher, J., Friedrichs, M., Guzman, A., Hain, C., Halverson, G., Hansen, J., Harding, J., Johnson, L., Kang, Y., Kilic, A., Minor, B., Morton, C., Ortega-Salazar, S., Ott, T., Ozdogan, M., Revelle, P., Ruhoff, A., Schull, M., Senay, G., Volk, J., Wang, C., Yang, Y., Anderson, R.G. 2021. OpenET: Filling the biggest data gap in water management for the Western United States. Journal of the American Water Resources Association. https://doi.org/10.1111/1752-1688.12956.
DOI: https://doi.org/10.1111/1752-1688.12956

Interpretive Summary: Competing water demands from agriculture, urban/industry and ecosystem use, along with increasingly variable supply in the form of rainfall and snowpack, are placing growing pressures on our limited global freshwater resources. To ensure sustainable agricultural production into the future, we need means for accurate measurement of consumptive water use (evapotranspiration, ET) at the scale of human management – the field scale. The OpenET project was developed to provide free and ready access to realtime ET information at 30-m spatial resolution developed from satellite remote sensing data. Prototype implementation is over the western United States, with potential for expansion U.S.-wide and ultimately full global coverage. OpenET is a collaborative effort between multiple ET modeling teams from NASA, USGS, USDA, academic institutions and non-profit organizations, and the tools are hosted on the Google Earth Engine (GEE) platform. This paper describes the OpenET system architecture as well as several use cases and partners that are currently testing data from OpenET in the West. The collaborative, user-driven approach used by OpenET may also serve as a reference in the future for teams working to develop analogous systems for remotely sensed measures of soil moisture and groundwater, or to implement operational forecasts of precipitation.

Technical Abstract: The lack of consistent, accurate information on evapotranspiration (ET) and consumptive use of water by irrigated agriculture is one of the most important data gaps for water managers in the western United States (US) and other arid agricultural regions globally. The ability to easily access information on ET is central to improving water budgets across the West, advancing the use of data-driven irrigation management strategies, expanding incentive-driven conservation programs, providing proper credit for investments in agricultural water conservation, and reducing transaction costs for water markets. ET data that can be easily accessed and that is seen as broadly accepted can also support adoption of innovative water management practices at scale, supporting meaningful progress toward increasing the reliability and sustainability of water supplies for agriculture. Recent advances in remote sensing of evapotranspiration (ET) have led to the development of multiple approaches for ET mapping at field scales (30m x 30m or 0.22 acres per pixel) that have been used for water resources management applications by US state and federal agencies. The OpenET project is building upon these advances to develop an operational system for ET mapping and to support further improvements in water management by increasing access to remotely sensed ET data. The OpenET project is developing a shared platform for data processing and distribution to provide automated and widely accessible ET data at user-defined scales and timeframes across the western US. OpenET is a collaborative effort involving six ET modeling teams from the US and Brazil, the Environmental Defense Fund, NASA, USGS, USDA, the Desert Research Institute, Habitat Seven, Google, six universities and key partners from the agriculture, water resource management, and conservation communities. The project is implementing an ensemble of satellite-based ET models on Google Earth Engine, which provides a shared computing platform where teams can collaborate on pre-processing of satellite, land cover and meteorological inputs to increase the consistency of data processing and reduce the range of estimates across the ensemble of models. The OpenET framework also includes reporting and data analysis tools, as well as open data services and an Application Programming Interface (API) to facilitate automated data retrieval and integration with other applications. The project is conducting an extensive intercomparison and accuracy assessment for the ensemble of ET models using ground measurements of ET from more than 130 flux tower sites instrumented with open path eddy covariance systems. OpenET is currently being tested by agricultural, water management and conservation partners and will be released to the public after incorporation of feedback from project partners.