Modeling Concepts - Coastal Lagoons: Ecosystem Processes and Modeling for Sustainable Use and Development - page 259

which are difficult to measure directly, could be defined as fluxes throughout the
entrance during salinity model simulations. These simulations can be calibrated with
annual salinity averages for the lagoon or with real salinity annual monitoring at
some lagoon points.

6.3.2.2 Water Budget Components

The water budget is the fundamental knowledge that should be obtained before any
hydraulic and water quality studies. The water balance of certain accuracy is helpful
to ensure that all sources and sinks of water of appropriate capacity are known. The
natural water budget in a lagoon is made up of contributions from surface evaporation
and precipitation, from river inflow and from exchanges at the ocean-lagoon bound-
aries. In some lagoons, bottom seepage may also be significant.
One can propose a convenient presentation of water budget components in the
form of a “rose” (Figure 6.14). According to the problem under consideration water
budget components may be estimated in absolute values, either in [m 3 s −1 ] or, more
practically, in [km 3 yr -1 ], as well as in specific values; for example, for the ratio of
an absolute value of each budget component to the open lagoon surface dimensions
are [m s -1 ] or [m yr -1 ]. Such a specific value describes the relative contribution of
each water budget component to variations in the lagoon volume. The ratios of the
average lagoon volume to the absolute value of each budget component (expressed
in seconds or years) provide clear characteristics of the significance of water budget
components for flushing the lagoon volume (see Section 6.3.3.1).

Precipitation

25

20

15

Evaporation

Underground run-off

10

5

0

Outflow from lagoon Marine influx

River run-off

Vistula Lagoon Darss-Zingst Bodden Chain

FIGURE 6.14 Lagoon water budget rose. Budget components are represented in specific values
(m ⋅ year −1 ) as a ratio of corresponding component absolute value to the lagoon free surface to
show the relative contribution of each water budget component to the lagoon volume.