Although the soundings depict the general trends in depths, they are unreliable because of continual scouring or shoaling due to changing river stages.  The areas which frequently shoal to the extent that passage of vessels drawing over 4 feet is difficult at extreme low water stages.
The Federal project provides for a shallow-draft channel, 6 feet deep at low water, from Sacramento to Colusa.  The Corps of Engineers conducts annual maintenance dredging operations to provide project depth.  Consult the District Engineer in Sacramento for controlling depths.