Case Studies - Coastal Lagoons: Ecosystem Processes and Modeling for Sustainable Use and Development - page 425

9.4.2 E COLOGICAL M ODELING AS A T OOL FOR T RANSBOUNDARY

M ANAGEMENT

Taking into account the political processes in the Baltic area, it is obvious that as a
border region shared by Poland and Russia, the Vistula Lagoon will remain under
different management approaches and strategies in the near future. Given the dif-
ferent priorities declared by national authorities, the substandard water quality of
the Vistula Lagoon is likely to degrade further.
The scientific community from both national regions in the catchment area of
the Vistula Lagoon (northern Poland and the Kaliningrad Region of Russia) intro-
duced the idea of developing a uniform tool to function as the basis of decision
making for Polish and Russian regional environmental authorities. This joint tool
had to be a numerical model, thereby ensuring a uniform quantitative approach to
water management in the Vistula Lagoon.
This experience was unique in that the scientific community began to combine
knowledge and efforts before the environmental authorities undertook cooperation
on the political level.

9.4.2.1 Numerical Model of the Vistula Lagoon

The MIKE21 model system was used as the basic model for the Vistula Lagoon.
This is a comprehensive modeling system for two-dimensional free surface flows
where stratification can be omitted. A number of add-on modules describe physical,
chemical, and biological processes related to environmental problems and water
pollution. 21
The following three modules of the MIKE21 model system were applied in the
study conducted in 1994-1997 by experts 9,10,19,20,22,23 from all the above-mentioned
Polish and Russian institutions and environmental authorities:

• MIKE21 HD is a hydrodynamic model that simulates water-level changes
and flows in shallow areas and forms the basis for calculations in the other
modules of the model system.
• MIKE21 AD is an advection-dispersion module which, coupled with the
HD module, simulates processes of the spreading of dissolved and sus-
pended substances under the influence of fluid transport and associated
natural dispersion processes.

• MIKE21 EU is a eutrophication module that describes nutrient cycles,

phytoplankton, and zooplankton growth as well as the general growth
of benthic vegetation and oxygen conditions. This module is integrated
with both previous modules, and calculations of hydrodynamics, trans-
port, and nutrient cycles are carried out simultaneously. The results
include phytoplankton carbon, nitrogen, and phosphorus; phytoplankton
production; detritus carbon, nitrogen, and phosphorus; zooplankton car-
bon; inorganic and total nitrogen; inorganic and total phosphorus;
benthic vegetation production; sediment oxygen demand; and Secchi
depth.