GPS has become an important tool both in navigation and in precise point positioning. One of the nuicance parameters limiting the accuracy of point determination is the water vapor content of the troposphere. On the other hand meteorologists are interested in the wet component of the troposphere as a valuable tool for Numerical Weather Prediction. Therefore GPS offers a low cost monitoring of water vapor with high temporal resolution. We make use of continuous measurements of the GPS/GLONASS reference station network in Austria, which currently consists of about 30 sites with distances ranging from 50 km to 120 km. We calculate the zenith wet delays for a period of 2 months (February and March 2002). Subsequently the results are compared to contributions of different processing centers of the COST-716 project ?Exploitation of Ground Based GPS for Climate and NWP? and with zenith path delay estimates provided by the IGS. As meteorologists need the water vapor within less than two hours, special attention is paid to the availability, reliability and especially to the quality of the satellite orbits used for the network calculations.