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

3. Data Analysis
The results from several analyses are reported in this section. A full representation of
the data is available in the companion data report (Behrens & Largier 2010). Here we
address specific issues:
(1) An estimate is obtained for water lost as seepage through the sand barrier at the
mouth by calculating a budget of water flow into and out of the estuary.
(2) Tidal flows and diurnal wind-driven seiche flows are quantified through an analysis of
data on current velocities and water level fluctuations.
(3) The spatial distribution of salinity is described, specifically addressing intrusion of
salinity upstream during open and closed periods.
(4) The spatial distribution of water temperature is described and changes during the
long closure event are outlined.
(5) The spatial distribution of dissolved oxygen is described, identifying locations and
times when anoxic or hypoxic conditions are found at depth.
(6) Stratification is quantified and analysis of the stability of this stratification provides a
measure of the likelihood of mixing between deep saline water and surface freshwater.
(7) A salt budget is calculated for the long closure event.
(8) An oxygen budget is calculated for the lower layer.
3.1 – Water budget & Seepage analysis
At the heart of the NMFS-proposed management protocol for the Russian River estuary
is the concept that water will escape from a closed estuary by seeping through the sand
barrier that separates it from the ocean. This will happen due to the rise of the elevation
of the estuary water level above that in the ocean (i.e., a scenario typically described as
a “perched lagoon”). This “seepage loss” may be accompanied by a flow of water over
the sand barrier (which is also known as the “berm”, referring to its wave-built origin).
Such an “overflow” at the mouth of the Russian River is not common in recent times
(PWA 2009), and the future flow rate is expected to be much lower than typical river
inflow rates in the past, even in dry years, so that a significant seepage loss is required
to maintain a steady water level in the estuary. Both overflow and expulsion of deeper
saline waters through the sand barrier occur in comparable smaller estuaries along the
coast of California, as noted in NMFS (2008).
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