Guadalupe River (California) - Guadalupe River Watershed

Guadalupe River Watershed

Historically, the Guadalupe River flowed into Guadalupe Slough, 1.0 mile (1.6 km) west of its current drainage into Alviso Slough. To make it easier to get sailboats up the Guadalupe River to the port of Alviso, the river was redirected into the straighter Alviso Slough by the 1870s. Alviso Slough, also known as Steamboat Slough historically, was relatively straight, while Guadalupe Slough meandered extensively through the marshes. Alviso Slough was historically not fed by any upland streams, but simply carried tidewater in and out of the extensive salt marshes.

The re-routing of the river to Alviso Slough in the 1870s also disconnected it from several tributaries, and had the effect of shrinking the Guadalupe River Watershed. San Tomas Aquino Creek (current) and its Saratoga Creek tributary (previously known as San Jon Creek and Campbell Creek) and Calabazas Creek (historic), used to enter the Guadalupe River upstream of Alviso. These tributaries were disconnected from the river and re-routed directly into Guadalupe Slough between 1876 and 1890 according to historic maps. Reportedly, Saratoga Creek (Campbell Creek) had steelhead and coho salmon runs. Large portions of the tributaries of the river were straightened and armored starting in the late 19th century and continuing through the 20th century first by farmers and then by the Santa Clara Valley Water District (SCVWD) and its predecessor organizations. They now go dry in the summer months and their lower segments have become denuded ditches requiring continuous maintenance. Mission Creek used to harbor trout and salmon but today it is buried in a culvert. The historic watershed can be viewed in the Thompson and West 1876 maps.

The Guadalupe Watershed today drains an area of 171 square miles (440 km2). Below its origination at the confluence of Guadalupe Creek and Los Alamitos Creek, the mainstem is joined by three other tributaries: Ross, Canoas, and Los Gatos Creeks. The SCVWD manages water flows (supply) and provides flood control on the river, and recently has started to promote watershed stewardship. Six major reservoirs exist in the watershed: Calero Reservoir on Calero Creek, Guadalupe Reservoir on Guadalupe Creek, Almaden Reservoir on Alamitos Creek, Vasona Reservoir, Lexington Reservoir, and Lake Elsman on Los Gatos Creek.