OpenET: Filling the Biggest Gap in Water Data for the Western United States (Invited Presentation)

Drought and water scarcity are becoming a chronic challenge across the western United States (U.S.). Ensuring adequate water supplies for food production while sustaining water supplies for towns, cities, rivers and wildlife requires careful management of water resources. ET data can be valuable in guiding irrigation management and scheduling to maximize crop production, supporting water trading programs, developing accurate water budgets, and enhancing water management strategies to sustain water supplies for agriculture, people and ecosystems. Developing innovative and effective water management strategies is difficult without accurate, consistent information about evapotranspiration (ET) from agricultural lands, the largest beneficial use of water by people in the western U.S.

Recent advances in remote sensing of ET have led to the development of multiple approaches for ET mapping that are advancing towards operational use by U.S. state and federal agencies. The OpenET project aims to integrate many of these advances 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.

OpenET is a collaborative effort involving six ET modeling teams from the U.S. and Europe, the Environmental Defense Fund, Google, NASA and key partners from the agriculture and water resource management communities. The project is implementing multiple satellite-based ET models (ALEXI/DisALEXI, METRIC, PT-JPL, SEBAL, SIMS and SSEBop) on Google Earth Engine. The OpenET platform uses data from Landsat to produce field-scale estimates of ET, and integrates data from multiple other satellites to produce ET data at a range of spatial and temporal scales. The ensemble approach used by OpenET is designed to ensure data continuity, and help to refine the strengths and accuracy of the different ET mapping methods over time. In addition, OpenET is developing a shared application programming interface (API) to provide consistent data access and a shared web-based user interface.

The OpenET platform will also facilitate intercomparison studies across different ET modeling approaches to increase understanding of the uncertainty associated with ET data from individual models, as well ensemble-based estimates. A key objective of the OpenET project is to increase understanding of the strengths and weakness of different approaches to ET mapping, and to identify and minimize errors and biases in all ET mapping approaches used within the OpenET framework.