264
J. FUrst and H. P. Nachtnebe1
4 Input of Nutrients
Concentrations of total phosphorus in the lake water of Alte Donau reached
approximately 40 Ilgr1 and were reduced to approximately 20 Ilgr1 by chemical
treatment. Concentrations of nitrate were in the range 300-450 Ilgr1. Based on the
results of the groundwater model and an intensified quality monitoring in
groundwater observation wel1s around the bank of the Alte Donau, a simple,
dynamic assessment of nutrient input could be performed to relate the nutrients in
the lake and the possible inputs from groundwater. Flows of phosphorus (P04-P,
total phosphorus) and nitrogen (nitrate, nitrite and ammonium) were computed for
discrete sections of the bank of the Alte Donau (Fig. 9). Phosphorus is the limiting
factor for eutrophication and will be briefly discussed here.
• ~12
Legend
• P04-P in Inflow [kg]
• P04-P in Outflow (kg]
O~~~~O'i;;5;;;;;;;;;;;;;;;;;;;;;;;j1 Kllometers
Fig. 9. Annual amount ofP04-P (kg yea{l) in groundwater flow into and out of Alte Donau
for the year 1997