THE QUANTIFICATION OF EVAPOTRANSPIRATION (ET) FOR SPECIFIC CROPS AND REGIONS IS REQUIRED FOR BASIN WATER BALANCE ESTIMATES FOR ESTIMATING STREAMFLOW AND GROUNDWATER DEPLETION STEMMING FROM IRRIGATION ACTIVITIES FOR IRRIGATION WATER MANAGEMENT FOR WATER USE REPORTING AND FOR REVIEW AND LITIGATION OF WATER RIGHTS APPLICATIONS TRANSFERS AND DISPUTES. THE USE OF SATELLITE IMAGERY IS THE ONLY WAY TO ACCURATELY ESTIMATE CROP ET UNDER ACTUAL FIELD CONDITIONS OVER LARGE AREAS IN A SPATIALLY EXPLICIT FASHION. BASED ON OUR TEAM S EXPERIENCE AND INTERACTIONS WITH WESTERN STATE WATER RESOURCE AGENCIES THERE IS A GREAT NEED FOR ACCURATE DEFENSIBLE AND TIMELY MAPS OF ET THAT ARE SUMMARIZED ON A FIELD-BY-FIELD BASIS THE SPATIAL SCALE AT WHICH WATER RIGHTS ARE MANAGED. THE MAIN GOAL OF THIS PROJECT IS TO DEVELOP AN OPEN-SOURCE OPEN-PLATFORM ET FRAMEWORK (OPEN-ET) THAT CAN BE USED BY WATER MANAGEMENT AGENCIES AND OTHER STAKEHOLDERS TO DEVELOP FIELD SCALE HISTORICAL AND OPERATIONAL ET AND CONSUMPTIVE USE (CU; ET MINUS PRECIPITATION) ESTIMATES FOR DECISION-SUPPORT OVER RELEVANT TIME PERIODS AND AREAS OF INTEREST. IN PARTNERSHIP WITH SEVERAL STATE AGENCIES WE WILL PROTOTYPE OPEN-ET AND DEVELOP A 10 YEAR ARCHIVE OF CROP ET AND CU ESTIMATES FOR PRIORITY AREAS OF INTEREST USING THE NASA EARTH EXCHANGE (NEX) AND MIGRATE OPEN-ET TO THE GOOGLE EARTH ENGINE CLOUD COMPUTING PLATFORM FOR OPERATIONAL STORAGE AND COMPUTE RESOURCES WEB-MAPPING VISUALIZATION OF GEOSPATIAL AND STATISTICAL SUMMARIES AND LONG-TERM SUSTAINABILITY. THE TECHNICAL TEAM WILL WORK WITH THE APPLICATIONS TEAM (WATER AGENCIES) DURING ALL PHASES OF THE PROJECT TO INCLUDE SYSTEM REQUIREMENTS DEFINITION STAFF TRAINING AND TRANSITIONING OF THE DEVELOPED TECHNOLOGY FOR OPERATIONAL USE AND SUSTAINABILITY. THIS APPROACH WILL ENABLE AGENCY STAFF TO GAIN A THOROUGH UNDERSTANDING OF THE MODELS ASSUMPTIONS AND LIMITATIONS SOFTWARE OPERATION AND POST-PROCESSING AND ULTIMATELY SUSTAIN INHOUSE ET MAPPING OVER THE LONG-TERM. EARTH OBSERVATION DATASETS WILL BE COMBINED WITH WELL-ESTABLISHED ET MODELS (METRIC SIMS) THAT HAVE BEEN DEVELOPED IN COOPERATION WITH WESTERN STATE AND FEDERAL AGENCIES AND HAVE BEEN USED FOR WIDE-AREA MAPPING OF CROP WATER USE. METRIC IN PARTICULAR IS A STATE-OF-THE-ART ENERGY BALANCE MODEL ACCEPTED BY SEVERAL COURTS AND OTHER OUTSIDE ENTITIES AND OFFERS A FORMAL TRAINING PROGRAM THAT HAS BUILT A SIGNIFICANT USER-BASE CENTERED IN THE WESTERN U.S. THE OPEN-ET FRAMEWORK WILL BE DEVELOPED TESTED AND APPLIED IN HIGH-PRIORITY STUDY AREAS OF FIVE WESTERN STATES: CENTRAL VALLEY AND PASO ROBLES COASTAL GROUNDWATER BASIN CA; BEAR RIVER BASIN ID/UT; TRUCKEE CARSON WALKER RIVER BASINS NV/CA; AND MALHEUR LAKE BASIN OR. THIS PROPOSAL DIRECTLY ALIGNS WITH THE SECOND COMPONENT OF THE SOLICITATION (AGRICULTURAL WATER USE) BY PROVIDING OPERATIONAL FIELD SCALE AGRICULTURAL ET TOOLS AND PRODUCTS AT MONTHLY TIME STEPS USING LANDSAT AND SENTINEL SATELLITE IMAGERY (WITH INTEGRATION OF VIIRS MODIS &PROBA-V AS NEEDED) AND LOCALIZED WEATHER STATION AND NASA GRIDDED WEATHER DATA. INNOVATIVE AGRICULTURAL ET TOOLS AND PRODUCTS WILL BE TESTED AND TRANSITIONED FOR IN-HOUSE USE BY WATER AGENCY CO-INVESTIGATORS FOR DAY-TO-DAY OPERATIONS AND SPECIAL STUDIES TO IMPROVE WATER MANAGEMENT DECISIONS RELATED TO IRRIGATED AGRICULTURE GROUNDWATER MANAGEMENT SURFACE AND GROUNDWATER RIGHTS ACCOUNTING AND IMPROVED UNDERSTANDING OF WATER AVAILABILITY AND SECURITY THROUGH ENHANCED KNOWLEDGE OF HISTORICAL AND CURRENT CONSUMPTIVE USE AND HYDROLOGIC BUDGETS.