Presented at the 2013 Aquarius/SAC-D Science Team MeetingThe present poster outlines the advances of the project Assimilation of Soil Moisture Estimates into Flow Forecasting Hydrologic Models (Aquarius/SAC-D Announcement of Opportunity). The project aims at developing assimilation techniques of SAC-D soil moisture retrievals into operational hydrologic models at catchments within the Del Plata basin. Since Aquarius soil moisture retrievals are to date not available, several essays with similar spaceborne sensors have been carried out. In a previous work, assimilation of AMSR-E X-band soil moisture content product from NASA/JPL was essayed resulting in model effinciency loss, while efficiency gain was observed with outflow data assimilation for the same basin and time period. In this study, a product based on MIRAS L-band of SMOS mission was used in a similar manner. Daily series of SMOS mean areal soil moisture content, observed outflow, TRMM 3B42RT mean areal precipitation and rain gauge-derived mean areal precipitation have been produced for the Gualeguay river basin. A modified Sacramento hydrologic model has been calibrated and validated for this basin using precipitation and outflow data. The modeled soil moisture is compared with SMOS soil moisture. A data assimilation algorithm is incorporated into the hydrologic model. Retrieved soil moisture is assimilated through this technique.