compared to Zone 2. In a review of dissolved oxygen conditions in Oregon estuaries (ODEQ, 1995), 
the opposite spatial pattern was found, with minimum DO levels occurring near the upper end of salt 
water intrusion and higher concentrations associated with inflow of ocean water. They also stated that 
greater frequency of low DO would be expected if sampling occurred near the upper extent of salt 
water intrusion. Our results demonstrate that this may not be the case. 
Figure 8.3 a) Time-series of dissolved oxygen and salinity and b) salinity versus dissolved oxygen 
showing import of hypoxic ocean water at a station 3.7 km from mouth of estuary. 
t t 
57 
Salinity, psu 
