An SF6 Tracer Study of the Flow Dynamics in the Stockton Deep Water Ship Channel: Implications for Dissolved Oxygen Dynamics

A sulfur hexafluoride (SF6) tracer release experiment was conducted in the Stockton Deep Water Ship Channel (DWSC) to quantify mixing and transport rates. SF6 was injected in the San Joaquin River upstream of the DWSC and mapped for 8 days. From the temporal change in SF6 distributions, the longitudinal dispersion coefficient (Kx) was determined to be 32.7±3.6 m s and the net velocity was 1.75±0.03 km day. Based on the decrease in SF6 inventory during the experiment, the pulsed residence time for waters in the DWSC was estimated at ∼17 days. Within the DWSC from Stockton downstream to Turner Cut, dissolved oxygen concentrations maintained a steady state value of 4 mg l. These values are below water quality objectives for the time of year. The low flow rates observed in the DWSC and the inability of oxygen-rich waters from downstream to mix into the DWSC upstream of Turner Cut contribute to the low dissolved oxygen concentration.