Groundwater Management Strategies to Improve Surface Water
259
underground sealing, reducing the interaction between surface water and
groundwater, with the effect of a significant decrease in the dynamics of
groundwater.
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163
162
161
160
159
158
157
158
155
154
_ I - water levels in Danube
- - Mean water levels 'Alte Donau'
-
Water levels 'Alte Donau'
I
I I
11
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II a
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Fig. 4. Hydrograph of the water level in the Alte Donau from 1961-1998
The most severe impact on the hydrological regime was caused by the Neue
Donau (New Danube) flood bypass channel, which is a parallel channel on the left
bank of the River Danube, separated from the main channel by an artificial island.
Its main influence on the groundwater flow between Danube and Alte Donau is
that its horizontal water level replaces the inclined water level of the main channel
as a boundary condition for groundwater flow. The water-level fluctuations in
Neue Donau were only about 50% of those in the main stream, and were further
reduced after impoundment of the Danube for the hydroelectric power plant
Freudenau (10 km downstream of Alte Donau) in 1996.
A well field for hydraulic enclosure of an old waste dump site in the area
between the upper part of Neue Donau and Alte Donau was installed already in
1994 as one element of restoration of the Alte Donau. It is mentioned in this
context, because its operation also significantly reduces groundwater seepage to
the Alte Donau.
3 Changes in the Water Balance of the Alte Donau
The water balance of the Alte Donau is determined by precipitation, evaporation,
inflow from and outflow to the groundwater. Precipitation and evaporation are