Location of the non-tidal current null zone in northern San Francisco Bay

Variations in Sacramento-San Joaquin River discharge into northern San Francisco Bay causes shifts in location of the bottom density current null zone. At a river flow of 2000 m³/s this null zone is approximately 20 km from the seaward end of the estuary, whereas at a river flow of 100 m³/s it is 80 km from the seaward end; the corresponding distances of salinity penetration are approximately 40 and 90 km from the seaward end. Seaward of the null zone, during low (summer) river discharge conditions, the inward-flowing bottom density current appears typically strong (5–15 cm/s) relative to the outward-flowing river current (river discharge per unit cross-channel area) of