Monitoring Program Design - Coastal Lagoons: Ecosystem Processes and Modeling for Sustainable Use and Development - page 323

correspond to both natural spatial current structures and the discreteness of the
simulation grid, but on the other hand, their number is usually limited because
this kind of field work is rather expensive. A formal technique for prior selection
of current measurement points in the lagoon area, proposed in Chubarenko
et al., 13 is based on the minimum current direction variation approach. Points of
measurements are chosen that represent the main structure of currents and that
have the minimum current variations during wind changes, i.e., the currents at
these points are sufficiently steady vs. the wind variations. If the model corre-
sponds well with reality at such points it is a sufficient basic level of model
calibration. If the model cannot reproduce the real currents at such points it must
be reconstructed.
The following step-by-step procedure to choose such points for control calibra-
tion measurements is proposed:

1. Determine the duration of measurements and the limited numbers of

points of measurements based on equipment and financial considerations.

2. Define the subareas with minimum range of current variations (absolute

values of current also must be considered to exclude stagnation areas)
that best represent the current spatial structure.

3. Make a final choice of limited measurement sites in these subareas with

regard to both local depth field and coastal line configuration.

The first and third steps involve human expertise. The second and key step may
be based on the formal mathematical procedure for preliminary simulations of
steady-state currents for 8 or 16 basic wind directions and typical wind speed
gradations. The current patterns obtained enable the total current structure in the
lagoon area to be determined. The subareas of jet-type stream, which are character-
ized by the minimum range of current direction variation, must then be selected.
The precise mathematical criteria to determine the jet-type current areas are defined
in Chubarenko et al. 13 Jet-type current is defined as the minimum range of current
vector variation that occurs, taking into account the ambient wind condition variation.

• The conservative tracer is used for calibration of the transport part of the

model (advection-dispersion). In the majority of cases salinity is used for
this purpose. It is a traditional measurement and equipment has been well
developed. Measurements of salinity variations in time and space provide
useful data for the water mixing and transport phenomena analysis and
especially for transport model calibration for synoptic or seasonal vari-
ability in a lagoon.

The points for calibration measurements should be assigned to represent all
important spatial differences in salinity in the lagoon area. First, the boundary values
for salinity should be measured—salinity concentration in lagoon entrances and
other inlet flows (rivers or artificial inlets). The frequency of measurements in the
lagoon entrances (as well as in other places of salinity inflows) should be synchro-
nized with level variation measurements or current measurements and should be