For planning a hydropower station at Paakitsup Akuliarusersua in West Greenland, some unusual hydrological studies were required. The basin is situated about 45 km north-east of Ilulissat/Jakobshavn (69° 30'N latitude) at the Greenland Inland Ice and is hence strongly ablation-influenced. As only sparse hydrological measurements had been obtained from the actual basin, it was necessary to base the calculations on historical data from Ilulissat/Jakobshavn. This work included among other things preparation of a suitable hydrological ablation model, detailed analyses of data to establish time series for the simulation work, sensitivity analyses of the hydro-glaciological prerequisites, and analysis and evaluation of periodic elements in the time series.