Geoscience Reference
In-Depth Information
Air
Boundary point
sources /sinks
Internal point
sources/sinks
Lagoon:
volume, surface area,
depth structure, currents,
concentrations,
temperature
Sea
Rivers
Internal extended
sources /sinks
Diffusive load
Bottom
Heat flux
Momentum flux
Mass flux
FIGURE 6.13
Principal model boundaries with mass, momentum, and heat fluxes. Arrows
show possible directions of fluxes.
Following this concept, the relationships between the lagoon and its surroundings
are presented in Figure 6.13. The boundaries are the air, the sea or other adjacent
basins, the bottom, the lagoon coastal zone including diffusive sources, rivers, and
internal natural extended point sources/sinks as well as artificial internal and bound-
ary influences.
The relationships between the lagoon and its external influences are prescribed
by exchanges of mass, momentum, and heat specified by corresponding fluxes
through all the boundaries. The fluxes are considered positive if they supply mass,
momentum, or heat to the lagoon, and negative otherwise.
The driving factors defining the exchange processes across the lagoon boundaries
can be subdivided into three groups:
•
Processes responsible for mass exchange: These are all water balance
terms, which also define the chemical and sediment balances in the lagoon,
the coastal and the bottom erosion and sediment deposition. For example
for salinity, the positive flux (input of the salt into the lagoon) is supplied
by marine water inflow, by evaporation, and sometimes by groundwater
infiltration if a salt-containing soil surrounds the lagoon. The total water
outflow toward the adjacent sea, precipitation, and freshwater inflow
(including fresh groundwater) will define the negative salt flux. Gain and
loss for constituents are considered as loads.
4a
They arise from different
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