connected to the sea, (figure 12). Let the evaporation minus the freshwater inflow be a
constant E. If the mouth is large enough the volume remains constant 
and
the load is 
where 
is the salt concentration of sea water. Consider a lake of volume connected to the sea, (figure 12). Let the evaporation minus the freshwater inflow be a
constant E. If the mouth is large enough the volume remains constant and
the load is where is the salt concentration of sea water.
Figure 12: Single lake cell connected via a level dependent estuary to
the sea.
Thus the concentration of the lake is
Now consider the effect of the closing the lake mouth. Then the load remains the same (
)
and the volume decreases. 
Clearly there is a singularity at time 
.
Now consider the derivatives.
Which is a constant.
Which starts at..
And increases without limit until the singularity of an empty lake.
Figure 13: Effect of mouth closure at low salinity.
Figure 14: Effect of mouth closure at high salinity.