The Oder Estuary - IOW

103
Atmospheric deposition (which constitutes small portion of the total nutrient load) and ground
water discharge (due to lack of data) are not included in the loads entering the Lagoon (WIELGAT,
2003). Inflows of Baltic waters to the Grosses Haff via Swina - the main connection of the Lagoon
with the sea - are taken into account in the model. It is assumed that no phytoplankton enters the
Grosses Haff directly, neither with riverine waters nor the sea waters, because due to changing
environmental conditions it dies when entering the Lagoon and is considered in the model as part
of detritus.
Since the Grosses Haff (Wielki Zalew) and Kleines Haff differ substantially in water retention time
the box model consists of two boxes representing two parts of the Lagoon separately. It is assumed
that 20% percent of the water flow from the Grosses Haff enters Kleines Haff and leaves through
the Peenestrom. This is a maximum value given in literature (MAJEWSKI 1980; MOHRHOLZ &
LASS 1998), ant it was chosen in order to account for possible mixing of water within the area of
both lagoons due to wind driven currents. Water penetrating into the Kleines Haff comes from the
Grosses Haff box, which implies that these waters have undergone full transformation in the
Grosses Haff.
2.2 Forcing functions
Long-term data bases contain data of different time resolution. To unify the system of model
calculations mean monthly values for all forcing functions were used in the model simulations.
2.2.1 Irradiance
The model uses data from the NOAA model (Mean Daily Visible Beam Downward Solar Flux at
Surface) as a forcing function – data available from NOAA-CIRES Climate Diagnostics Center,
Boulder, Colorado, USA. http://www.cdc.noaa.gov/ (NOAA, 2002). Daily values expressed in
Wm -2 obtained from the NOAA model were averaged into monthly values.
2.2.2 Temperature
Water temperature for the Szczecin Lagoon was obtained from the regular monitoring programs
carried out in the Grosses Haff by the Westpomeranian Inspectorate of Environmental Protection
(WIOS) in Szczecin/Poland and in the Kleines Haff by the Landesamt für Umwelt, Naturschutz
und Geologie Mecklenburg-Vorpommern (LUNG) in Güstow/Germany. Also unpublished data
from measurements conducted by the Research Station of the Sea Fisheries Institute in Swinoujscie
were used. Most measurements were carried out once a month during vegetation period only
between April and November. Due to data scarcity measurements for Grosses Haff and Kleines
Haff were averaged to one monthly value for the entire Lagoon.
2.2.3 Nutrient loads from the Oder River
The main source of riverine water in the Lagoon is the Oder River, comprising 97% of the total
inflow to the Lagoon, based on measurements done at the Roztoka Odrzanska cross-section
(MAJEWSKI 1980). Data on the mean monthly Oder River flow are obtained from data by IMWM
(1980-83; 1987-2000) from the gauge station located at Gozdowice (Figure 1.1). Nutrient
concentrations, measured at the Krajnik Dolny cross-section, were obtained from the
Westpomeranian Inspectorate of Environmental Protection (WIOS) in Szczecin/Poland. Monthly
loads of nitrogen and phosphorus discharged from the Oder River where calculated by multiplying