HYDROGEOLOGICAL ASPECTS OF QUATERNARY SEDIMENTS IN POLAND

Abstract

Abstract. The major groundwater resources in Poland come from Quaternary aquifers. Rich in groundwater are structures of contemporary river valleys and of buried valleys, that comprise sands and gravels of glaciofltivial origin. Groundwater aquifers cover water demands of ca. 2.1 km3annually. 65% of drinking water in Poland comes from groundwater intakes. Recharge zones of these aquifers are usually located in highlands - moraine plateau, and discharge zones are located in deep and wide river valleys. The average thickness of fresh water aquifers is about 200 m in Poland. The fresh water was stated even over 1,000 m depth in some places, but in the Mesozotc strata. The thickness of fresh water aquifer reduces, however, to only few metres in areas of salt water ascension or intrusion along the Baltic coast area. Recognition of groundwater circulation systems is the basis for delineation of a groundwater body (GWB) In Poland, the most productive parts of groundwater bodies that allow to abstract water at a rate grater that 10,000 m3/day, are defined as Major Groundwater Basins (MGWBs). The mean residence time of groundwater in Quaternary aquifers in Poland is estimated at some 50 yrs. whereas the residence time of water in sluggish circulation systems in deeper strata exceeds !04 yrs. Quaternary aquifers situated close to the surface area are vulnerable to municipal and agricultural pollution. The geogenie pollution such as sea water intrusion or ascension of brines are observed mainly at lowlands along the Baltic coastline, in vicinity of water intakes, or on an axial zone of anticlinoria. Trends in lowering a groundwater table are noted in the central part of the Polish lowlands and are associated with climatic variability or lignite opencast dewalering.