AGRICULTURE IS THE LARGEST WATER USER IN THE UNITED STATES, ACCOUNTING FOR 80-90% OF HUMAN WATER CONSUMPTION IN THE ARID WEST. IMPROVING WATER RESOURCE MANAGEMENT REQUIRES A DEEPER UNDERSTANDING OF KEY FACTORS INFLUENCING AGRICULTURAL WATER USE. THE GOAL OF THIS PROJECT IS TO ADDRESS THIS NEED BY IDENTIFYING THE KEY ECONOMIC, BIOPHYSICAL, CLIMATE, AND, INSTITUTIONAL FACTORS INFLUENCING FARMERS' WATER APPLICATION RATES AND IRRIGATION TECHNOLOGY ADOPTION ON THE U.S. WEST COAST (CALIFORNIA, OREGON, AND WASHINGTON). THE SPECIFIC OBJECTIVES ARE: 1) CREATE A PROFILE OF WATER AND CLIMATE VARIABLES AFFECTING SPECIFIC CROPS, INCLUDING THE TIMING DIMENSIONS OF THESE VARIABLES AND WHETHER THERE ARE "UPSIDE" OR "DOWNSIDE" RISKS; 2) DEVELOP CROP-SPECIFIC DATABASES ON SPATIAL AND TEMPORAL VARIATIONS OF IMPORTANT CLIMATE VARIABLES AFFECTING CROP PRODUCTION ON THE WEST COAST; 3) DEVELOP A DATABASE TO CHARACTERIZE WATER AVAILABILITY, WATER SUPPLY INSTITUTIONS, IRRIGATION TECHNOLOGY, AND WATER USE ACROSS FARMS ON THE WEST COAST; 4) DEVELOP A FARM-LEVEL MODELING SYSTEM TO UNDERSTAND HOW WATER AVAILABILITY, WATER SUPPLY INSTITUTIONS, CLIMATE, AND EXTREME WEATHER AFFECT FARMERS' CROP CHOICE, WATER USE AND IRRIGATION TECHNOLOGY ADOPTION FOR SPECIALTY CROPS, GRAIN, AND FORAGE CROPS ON THE WEST COAST; 5) USE THE MODELING SYSTEM TO ANALYZE HOW FARMERS WOULD RESPOND TO CHANGES IN CLIMATE AND WATER POLICY AND TO UNDERSTAND THE BARRIERS OR DISINCENTIVES TO ADOPT EFFICIENT IRRIGATION TECHNOLOGIES; AND 6) COMMUNICATE FINDINGS TO INFORM POLICY ON WATER RESOURCE MANAGEMENT. OUR APPROACH WILL BE TO DEVELOP UNIQUE WATER AND CLIMATE DATABASES AND CONSTRUCT WATER USE AND IRRIGATION TECHNOLOGY ADOPTION MODELS, CAPITALIZING ON THE EXPERTISE OF FACULTY IN THE PRISM CLIMATE GROUP, PLANT SCIENCE AT UC DAVIS, AND APPLIED ECONOMICS AT OREGON STATE UNIVERSITY. THIS PROJECT WILL PROVIDE VALUE TO SOCIETY BY SUPPORTING INFORMED PUBLIC AND PRIVATE DECISION MAKING FOR MANAGING WATER SCARCITY AND CLIMATE VARIABILITY ON THE U.S. WEST COAST.