The annual precipitation average is 1170 mm, which corresponds to a precipitation volume of some 100 billion cubic meters per annum. About 55 billion cubic meters of this rain water run off into water bodies, whereas 45 billion cubic meters simply evaporate into the atmosphere. The above figures determine the hydrological balance for the period of 1961 to 1990.
Major groundwater reserves in Austria
About 45 percent of the federal territory ? namely the Central Alps, the Bohemian mountains, and the pre-Alpine region ? have only scarce cave water resources.
Essential water reserves are found in the karst terranes of the Northern and Southern Kalkalpen with their partly abundant karst water reserves. About one quarter of the total precipitation goes down in this area, which covers 20 percent of the national territory of Austria.
About 15 percent of the federal territory are covered by the alternately permeable tertiary rock formations of the pre-Alpine region.
The remaining 20 percent of the national territory are covered with Pleistocene and Holocene sediments, found in the pre-Alpine region and in the valleys and basins of the Alps with partly enormous pore water resources.
Groundwater volume can only be estimated
Due to a mere approximation of parameters, the groundwater volume in Austria can only be roughly estimated. There are:
- l 40 billion cubic meters of pore water in quaternary and 20 billion in tertiary and comparable sediments,
- 15 billion cubic meters of karst water,
- five billion cubic meters of crevice water, and
- an unknown quantity of profound groundwater.
This makes an overall groundwater volume of approximately more than 80 billion cubic meters. There is an additional volume of about ten billion cubic meters of soil water. The water volume of Lake Attersee, by comparison, amounts to four billion cubic meters, that of Lake Constance to 48 billion cubic meters. Among the profound groundwater reserves that cannot possibly be estimated are mineral springs and hot springs.
Ways to calculate the annual groundwater recharge
The average annual low water flow, which mainly stems from groundwater resources, serves as a reference to estimate the annual amount of groundwater recharge. If we take all relevant Austrian water bodies, this water flow is in all about 1,000 cubic meters per second. The mean groundwater recharge or annual groundwater flow rate amounts to 30 billion cubic meters, corresponding to 57 percent of the total rainwater runoff of 55 billion cubic meters, or 30 percent of the total precipitation volume.
In Austria, about three billion cubic meters of groundwater ? 50 percent pore water, 50 percent karst water ? are extracted to satisfy the total water demand per year. This makes ten percent of the average annual groundwater recharge volume.
Due to the enormous regional and temporal differences in precipitation, it may happen that in some years certain parts of the Austrian territory ? especially the east of Austria ? suffer from little or no groundwater recharge. The sustainable use of groundwater resources in a region depends on the current rate of groundwater recharge. (Source: aqua press Int. 1A/1998)
Dipl. Ing. Dr. Franz Pramberger
Information & Contact:
Dipl.-Ing. Dr. Franz Pramberger,
Federal Ministry of Agriculture, Forestry, Environment and Water Management, Hydrographisches Zentralbüro,
A-1030 Wien, Marxergasse 2,
Phone: +43 1 71100-6941
