Artificial groundwater recharge in Freisach and Andritz
Topic of the practice
Use of artificial groundwater recharge to sustain the good quality drinking water supply of the second largest city in Austria
Good Practice Information
The waterworks Friesach and Andritz, which cover 70 % of the water demand of the city of Graz with approximately 250.000 inhabitants, operate by means of artificial ground water recharge plants where horizontal filter wells serve as drawing shafts. The ground water recharge systems serve to increase the productivity of the aquifer and to reduce the share of the infiltration from the river Mur. Protection areas have been identified to ensure that the water quality of the aquifer stays at optimal levels. The protection areas are divided into zones indicating various restrictions for usage and planning. Two respective streams serve as the source for the water recharge plants. The quality of the surface water is measured by means of a turbidity meter and if the turbidity of the water exceeds a defined level, water withdrawal is automatically stopped. After passing through intake- and sedimentation tanks, the water enters a horizontal gravel filter system and the infiltration plants.
Different infiltration systems are utilised. The sand filter and lawn basins and operate continuously, the infiltration trenches however operate intermittently. Each of the various artificial ground water recharge systems displays specific advantages and disadvantages in terms of operation as well as maintenance which have to be taken into account before selecting an infiltration plant.
Evidence of success
The practice can be considered as good example for sustainable use and also reuse of scarce resources. Since artificial recharge is a low cost technique it can be easily transferred to regions where water resources are less abundant. However, the raw water quality, which can be improved during the subsurface passage, is key to the success of artificial groundwater recharge. The value of it can be expressed in the cost that arise if water supply would have to covered by different means, e.g. by seawater desalination. Furthermore, artificial groundwater recharge might serve other purposes like storing stormwater runoff, thus replacing costly surface reservoirs, or avoiding mixture of good quality groundwater with polluted groundwater parts.
Contact details to obtain further information on the practice
Harald Schmölzer, Franz Gundacker
Holding Graz Services; water supply
Annex completed on: 08-09-2011