Hydrography of the Russian River Estuary - Sonoma County Water ...

During the late-October closure, stability at Freezeout Creek was higher than previously
observed as a result of a higher salt mass in the estuary. This was probably due to a
large wave event at the time of closure. Following closure, this salt mass intrudes
landward, introducing more sub-pycnocline to Freezeout Creek and thus enhanced
stability.
3.5 – Salt and oxygen mass budgets
3.5.1 – Salt budget for estuary
Given that salt is neither created nor destroyed on the time scale of interest in this
study, the total mass of salt contained in the estuary is conserved in the absence of
inflows or outflows of saline water. It is unaffected by processes, such as river inflow,
evaporation, mixing, or density-driven exchange flows. Thus one can learn much about
the estuary by tracking the salt mass. A gain of salt implies a gain of saline water (i.e.,
seawater) and a loss of salt implies a loss of saline waters from the estuary. Of specific
interest is the possible loss of estuary water via seepage through the sand barrier, as
addressed through a water budget (Section 3.1).
To calculate the mass of salt from CTD profile data, the estuary was divided into
segments (Figure 3.37), and each segment was divided into incremental volumes in the
vertical direction. These incremental volumes were multiplied by CTD measurements of
salinity at corresponding depths and summed up over the total depth to obtain a salt
mass for each segment for each time a CTD profile was obtained. The total mass of salt
in the estuary is obtained from a sum of all segments. For this analysis, the upper
boundary is taken as Freezeout Creek, since the upstream pool at Moscow Bridge
received only negligible amounts of salt during the monitoring period.
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