In this thesis the chloride concentration in the groundwater of the Mur river basin from Graz to Bad Radkersburg is analysed with the aim to illustrate the temporal and spatial variability, to detect the anthropogenic sources of chloride and to show possible areas of risk.Chlorides are chemical combinations with chlorine and belong to the group of anions. Naturally pore groundwater systems, like the investigation area, normally have chloride concentrations between 10 and 30 mg/l, which is the result of the geogenic entry out of soil. Higher concentrations show the influence of anthropogenic sources.Agricultural fertilizers contain chloride. According to the cultivation a variable amount of chloride is transported from the soil to the groundwater.On the streets in Austria every year 200.000 to 300.000 tons of road salts are used. Road salts contain chloride in the form of sodiumchloride, magnesiumchloride and calciumchloride. The ?Trinkwasserverordnung? and the ?Österreichisches Lebensmittelbuch? define a guideline value of 200 mg/l chloride. Below this value the groundwater is permitted as drinking water. The results of the data analysis indicate clearly, that the chloride concentrations in the groundwater of the Mur river basin from Graz to Bad Radkersburg are strongly influenced by anthropogenic sources. The road salts on the streets are the anthropogenic main source and the agriculture leads to moderate chloride entries into the groundwater on big areas. A reduction of the chloride values is done by dilution of the groundwater with surface water.Concerning to the chloride concentrations the groundwater in the whole investigation area can be used as drinking water so far. The development of the chloride concentrations in the areas of Graz-Liebenau, Unterpremstätten/Kalsdorf, Weitendorf bei Wildon, Jöß and Landscha should be monitored more precisely and the construction of drainage systems would be a recommended measure.