High Quality Content by WIKIPEDIA articles! High Quality Content by WIKIPEDIA articles! Specific storage (Ss), storativity (S), specific yield (Sy) and specific capacity are material physical properties that characterize the capacity of an aquifer to release groundwater from storage in response to a decline in hydraulic head. For that reason they are sometimes referred to as "storage properties". In the field of hydrogeology, these properties are often determined using some combination of field hydraulic tests (e.g., aquifer tests) and laboratory tests on aquifer material samples.