THE UPCOMING NASA/CNES SURFACE WATER AND OCEAN TOPOGRAPHY (SWOT) MISSION WILL MEASURE SURFACE WATER ELEVATION (WSE) WORLDWIDE FOR THE FIRST TIME STARTING IN 2021. WHILE NO SATELLITE INSTRUMENT HAS BEEN INVENTED THAT CAN DIRECTLY MEASURE RIVER DISCHARGE MERGING SWOT WSE MEASUREMENTS WITH HYDROLOGIC AND HYDRAULIC MODELS IS A PROMISING TECHNIQUE FOR INFERRING WHAT RIVER DISCHARGE MOST LIKELY RESULTED GIVEN THE OBSERVED WSE. UNLIKE CONVENTIONAL RETRIEVAL ALGORITHMS THIS METHOD CALLED DATA ASSIMILATION (DA) CAN ESTIMATE DISCHARGE AT LOCATIONS AND TIMES NOT CAPTURED BY THE SWOT OVERPASS. THIS STUDY WOULD USE AN OBSERVING SYSTEM SIMULATION EXPERIMENT TO ASSESS THE PERFORMANCE OF DIFFERENT DA APPROACHES FOR ESTIMATING DISCHARGE IN THE FACE OF BIASED FORCING DATA IN TWO LARGE RIVER BASINS IN DIFFERENT PARTS OF THE WORLD. THE LATEST VERSION OF THE SWOT INSTRUMENT SIMULATOR WILL BE USED TO GENERATE REALISTIC MEASUREMENT ERRORS. ADDITIONALLY THE BENEFITS OF USING SEQUENTIAL VS. BATCH ESTIMATION AND KALMAN VS. PARTICLE-BASED DA APPROACHES WILL BE STUDIED WITH A FOCUS ON HOW BASIN CLIMATOLOGY AND TOPOGRAPHY AFFECTS DA PERFORMANCE