The problem of predicting the groundwater level in an urban subarea
published: Mar 1, 2016
ArtNo. ESP171016701003, Price: 29.00 €
The German capital Berlin is one of the megacities that abstract their groundwater only within the city limits. The currently rising groundwater level in Berlin-Siemensstadt causes technical and economical problems, which require assessing future risks. A local prognosis could be based on only one nearby groundwater observation station. The water level observed here from 1931 to 1943 and from 1949 to 2004 shows an erratic course. It has been mathematically modelled by time series analysis. Quadratic polynomial trend functions can be fitted with sufficiently high statistical significance in each case but auto-correlation analysis and geostatistical variography do not result in defined ranges of influence. Cross correlation analyses show that the fluctuations of the groundwater level are not primarily influenced by important natural factors such as by precipitation, temperature and sunshine duration. The results of a historical analysis show that the observed fluctuations depend, first of all, on the human activity in the city, such as extraction of groundwater, sealing of the ground, construction activities, drainage of the precipitation and mainly on the general demographic and economic development of Berlin. But in practice, the development of these factors is imponderable over decades. Consequently, a reliable prediction of the groundwater level over decade-long timescales seems to be impossible. Although mathematical methods are well-established tools to predict the local long-term development of a groundwater level also in densely populated urban subareas, they fail if moreover self-sustaining near-surface unconfined groundwater is extracted from such locations. It can be cautiously predicted for the study site that the groundwater level can rise closely to the pre-industrial level if no human-made interruptions take place. The level will remain somewhat deeper due to the extensive sealing of the ground, drainage of the precipitation and partly ongoing water extraction.