Sacramento–San Joaquin River DeltaCalifornia’s Green Trade Corridor, is part of the Stockton Deepwater Shipping ChannelMap showing the San Joaquin River
At the time of the 1849 California Gold Rush ocean steamboats could travel up the San Joaquin River to Fresno. As San Joaquin Valley grew agriculturally and river water was used for crops, the river became shallow. With slower moving water, silt began to build up in the river and it became even shallower. By 1890 the city of Stockton had lost its importance as a seaport. By 1910 the city had created proposals to increase the depth of the lower river by dredging; however, the plans were delayed by World War I. In 1925 the city began a $1.3 million bond campaign dedicated to dredging the lower San Joaquin.[2][3][4]
Stockton partnered with the federal and state governments in 1926 to form a $8.2 million fund to change the river to a new channel. In 1928 the river-channel project began. The river was both widened and deepened. To straighten the river, meanders and oxbow lakes were removed.[5] Major straightening cuts were built at Hog Island, Venice Island and Mandeville Island, along with five minor straightening cuts. The new deepwater channel was now 4 mi (6.4 km) long and had a depth of 37 ft (11 m). As silt build-up still continues, major dredging was performed in both 1968 and 1982.[6] The Stockton Deep Water Ship Channel can handle fully loaded ocean vessels of up to 60,000 short tons (120,000,000 lb; 54,000,000 kg) and up to 900 ft (270 m) long.[7]
Environmental concern
The slowing of the river-channel has unexpectedly caused low dissolved oxygen levels in the lower San Joaquin River water. The low dissolved oxygen has hurt the fish populations. The three causes are the straightening of the river, pollution from the harbors and cities, and poor tidal mixing.[8]
