The present annual flow of the San Joaquin River near Vernalis is about , or 4.5 million acre-feet (5.6 million dam3) per year. According to USGS stream gauge #11303500 at Vernalis, above Suisun Bay and below the mouth of the Stanislaus River, the average discharge of the San Joaquin River between 1924 and 2011 was , or 3.3 million acre-feet (4.0 million dam3) per year. The highest recorded annual mean was , 15.4 million acre-feet (19.0 million dam3), in 1983, while the lowest was , , in 1977. The maximum peak flow occurred on December 9, 1950 at , and a low flow of was recorded on August 10, 1961.