Seite - 253 - in Book of Full Papers - Symposium Hydro Engineering

the dam owner and operator Thüringer Fernwasserversorgung to increase water withdrawal in the future. On the other hand, with an already fully committed water budget, any long-term or sudden changes in the dam’s inflow regime would have a direct impact on safe yield. Safe yield water withdrawal is constricted by the precipitation and runoff regime of the 5.32 km2 catchment area and the total available storage volume of 1.24 MCM. When updating the long-term operational plan of the dam, the owner/operator carried out an analysis of the water balance using historic records. The following questions were guiding the analysis:  Did significant changes of meteorological parameters and runoff occur in the last 100 years?  Were these changes gradual or sudden?  What are the implications for dam operations and which mitigating measures could be put in place? 2. MATERIALS AND METHODS The location of the dam site and surrounding area is given in Figure 1. Temperature data were taken from Braunlage and Artern met stations (data source: DWD). Precipitation records were taken from three nearby stations (see Figure 1). Fig. 1. Location of Neustadt dam and the location of measurements. Artern met station (not depicted) is located 37 km southeast oft he dam site A proxy for the onset and duration of the vegetative season, during which active transpiration does occur, was estimated as the temperature sum above the 253