The Oker river and its major tributaries are draining the northern Harz
Mountains and its foreland. The Oker drainage covers 1825 km². Its
headwaters in the Harz Mountains are situated at an altitude of 900 m a.s.l.
The hilly Harz foreland (100-200 m a.s.l.) is characterized by fertile
loess soil and intensive agriculture. To the north of Braunschweig the
loess layer is changing to sand soils of the Lower Saxonian Lowland. Braunschweig
is the capital of this region in southeastern Lower Saxon. The average
of annual precipitation is varing between 1300 mm (Harz) and 600 mm (Braunschweig),
which is in a rain shadow produced by the Harz Mountains.
Study area and its position within the Federal
Republic of Germany
