EPISODIC DROUGHTS, GROUNDWATER DEPLETION, AND GROWING WATER DEMAND ARE HAMPERING THE SUSTAINABILITY OF IRRIGATED AGRICULTURE. MANAGED AQUIFER RECHARGE (MAR) IS INCREASINGLY USED TO AUGMENT GROUNDWATER SUPPLIES WITH EXCESS SURFACE WATER USING TECHNOLOGIES SUCH AS DRYWELLS AND FLOODING OF AGRICULTURAL LAND (AGMAR). THE GOAL OF THIS PROPOSAL IS TO EVALUATE THE INDEPENDENT AND JOINT USE OF AG-MAR AND DRYWELLS WITH PRETREATMENTS (TO REMOVE SEDIMENTS AND CONTAMINANTS) TO SYNERGISTICALLY OVERCOME LIMITATIONS OF BOTH APPROACHES. WE PLAN TO INSTRUMENT AT LEAST ONE DRYWELL, ONE AGMAR SITE, AND SEVERAL MONITORING WELLS ON TERRANOVA RANCH (HELM, CA) WITH SENSORS TO MONITOR WATER INPUTS, INFILTRATION, RECHARGE, AND SOIL AND WATER QUALITY PARAMETERS. THE SITE WILL BE THOROUGHLY CHARACTERIZED FOR SOIL HYDRAULIC AND SOLUTE TRANSPORT PROPERTIES. COLLECTED DATA WILL BE USED WITH MATHEMATICAL MODELING TO INVERSELY DETERMINE PARAMETERS, DESIGN IMPROVED MAR STRATEGIES THAT OPTIMIZE WATER QUANTITY AND QUALITY, AND TO PREDICT THE LONG-TERM PERFORMANCE OF BOTH MAR STRATEGIES. JOINT OPERATION OF DRYWELLS AND AG-MAR ARE EXPECTED TO: (I) ENHANCE THE INFILTRATION RATE AND MAR OPPORTUNITIES THROUGHOUT THE YEAR; (II) REDUCE THE FLOODING TIME AND PREVENT CROP DAMAGE FROM OXYGEN DEPLETION; (III) ENHANCE RECHARGE BY BYPASSING LOW PERMEABILITY LAYERS; (IV) DECREASE VADOSE ZONE STORAGE AND LEACHING OF IN-SITU CONTAMINANTS; AND (V) IMPROVE RECHARGE WATER QUALITY FROM THE DRYWELL PRETREATMENT. OUR RESULTS ARE EXPECTED TO INCREASE THE WIDESPREAD ACCEPTANCE OF ON-FARM MAR TECHNOLOGIES FOR INCREASED GROUNDWATER SUSTAINABILITY AND LONG-TERM VIABILITY OF IRRIGATED AGRICULTURE, AS WELL AS PROVIDE GOVERNMENT REGULATORS WITH CRITICAL SCIENCE-BASED FINDINGS AND TOOLS TO MANAGE WATER RESOURCES.