A SIMPLIFIED METHOD OF REGIONAL GROUNDWATER VULNERABILITY ASSESSMENT Andrzej J.Witkowski & Andrzej Kowalczyk: University of Silesia, Department of Hydrogeology and Engineering Geology, ul.Będzińska 60, 41-200 Sosnowiec, Poland, e-mail:
[email protected]
Assessment of the intrinsic vulnerability of the major groundwater basins in Poland is based mainly on the evaluation of vertical travel time of conservative contaminants from the land surface to the aquifer (Kleczkowski, 1990, Witczak & Żurek, 1994, Macioszczyk, 1999, Duda et al., 2003). There are two formulae commonly used to calculate travel time:
1) implemented by Witczak & Żurek (Witczak & Żurek,1994): mw ta = a o (1) Pω e 2) modified by Macioszczyk Bindemann’s formula (Macioszczyk, 1999): ma wo ta = (2) 3 ( Pω ) 2 k ' e where: ta – travel time [t] ma – thickness of the unsaturated zone [L] wo – average moisture content of the strata in the unsaturated zone [-] P – mean annual precipitation [L/t] ωe – effective infiltration coefficient [-] k’ – vertical hydraulic conductivity of the unsaturated zone [L/t]
Accurate assessment of vertical travel time requires reliable data that are often unavailable. Classification of an aquifer into vulnerability classes is based on the geological framework as well as the hydrogeological characteristics and does not necessarily include detailed consideration of the vertical travel time. A long-term programme of research carried out in Upper Silesia and its peripheries, has enabled a simplified method of groundwater vulnerability assessment to be devised for the major aquifers (Quaternary, Triassic, Jurassic and Carboniferous) (Table1). The method builds on experience related to estimations of major groundwater basins (MGWB) vulnerability within the region and on existing methodologies (Foster, 1987, Kleczkowski ed., 1990; Adams & Foster, 1992; Różkowski et al., 1997; Foster et al., 2002; Duda et al., 2003). It takes into account the current Polish classification of major aquifer vulnerability: very high (travel time t
