Podatność wód podziemnych na zanieczyszczenie jako czynnik determinujący stopień ich zagrożenia - na przykładzie zlewni Mogilnicy
Wydawnictwo Poznańskiego Towarzystwa Przyjaciół Nauk
The dynamics and tendency of change in surface- and groundwater systems depend, among other things, on their susceptibility to various kinds of natural and man-made factors as well as the intensity and duration of their impact. The study presents stages in the assessment of the vulnerability of shallow groundwater to the migration of pollutants coming from the land surface. It was carried out for a typical agricultural catchment situated in the Wielkopolska Lowland (the Mogilnica catchment). Following the basic assumptions of the ranking methods of assessment of groundwater vulnerability (the GOD index), an analysis was made of a selected group of physical parameters of the catchment, including hydrogeological elements which determine the response and resistance of shallow aquifer systems to the impact of man-made factors. Empirical formulae (Bachmat and Collin’s) were employed to calculate the potential time taken by the pollutants to reach the water-bearing horizon, which provided a basis for a classification of the extent and degree of risk to groundwater. The areal distribution of the index of groundwater vulnerability to pollution was presented and analysed against information about the way of development and land-use pattern in the catchment. It was found that its groundwater displayed a low degree of vulnerability due to the fact that most of the catchment area is covered with till which screens the shallow groundwater from the inflow of pollution. An assessment of risk to groundwater resulting from the time of migration of water through the aeration zone showed that more than half of the study area (about 56%) was at medium risk and nearly 20% was at high risk. This means that the migration of potential pollutants can take from 5 to 25 years and from 2 to 5 years, respectively. Attention was also paid to the numerous links of shallow groundwater with surface waters and the deep groundwater system of the Wielkopolska Buried Valley, which is the principal operable aquifer in the study area. Taking into consideration the level of human impact in the catchment, areas least and most exposed to risk were identified; they should be considered especially carefully when planning new investment. The quantification of parameters of the individual catchment subsystems, including the shallow groundwater system, is a starting point for analyses of spatial variability of the parameters and for comparative studies of various units, e.g. catchments, groundwater bodies, or areas with similar land-use patterns. An assessment of the degree of vulnerability of groundwater to pollution can be a crucial element in the preparation of a strategy of sustainable management of water resources in the catchment.
Badania Fizjograficzne, Seria A, Tom 58, 2007, s. 179-201