The Oder Estuary - IOW

2 The Oder river load
The Oder-catchment has a surface area of about 120,000 km 2 . With a length of 854 km and a longterm
average water discharge of 574 m³/s the Oder river belongs to the five most important rivers
in the Baltic region. The Oder contributes about 4 percent to the 15,000 m³/s water discharge,
which enter the Baltic Sea (HELCOM 2002). The population of about 13 Mio inhabitants and
intensive agricultural utilization are responsible for the high nitrogen and phosphorous loads of the
Oder river. Between 1994 and 1998 the Oder contributed more than 10 % of the phosphorus load
and nearly 10 % of the nitrogen load into the Baltic Sea.
t/a
90000
80000
70000
60000
50000
40000
30000
20000
10000
0
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
Figure 2.1: Oder river discharge and annual nitrogen load (NH4-N and NO3-N) near Schwedt, 116
km upstream (BEHRENDT et al. 1999).
t/a
8000
7000
6000
5000
4000
3000
2000
1000
0
1980
1982
1984
1986
1988
1990
1991
1992
1992
1993
1994
1994
1995
900
800
700
600
500
400
300
200
100
0
900
800
700
600
500
400
300
200
100
0
m 3 /s
m 3 /s
NH4-N
NO3-N
Abfluß
PO4-P
Pt
Abfluß
Figure 2.2: Oder river dicharge and annual phosphorus load (PO4-P und Pt ) near Schwedt, 116 km
upstream (BEHRENDT et al. 1999).
The nitrate load (Fig. 2.1) is closely linked to the water discharge. The higher the discharge, the
higher the nitrogen loads. The observed nitrate concentration of about 2.5 mg/l in the river was
stable between 1986 and 1998 (HELCOM 2002) due to the fact that ground water is the major source
19