BALWOIS 2004 Ohrid, FY Republic of Macedonia, 25-29 May 2004

Vulnerability Evaluation Of A Mutilayer Aquifer For A Sustainable Use Of The Resources (Western , )

V. Liguori, V.Rametta Università di Palermo Palermo, Italy

Abstract This paper is intended to describe the water environmental status in the Plain of Castelvetrano and (Western Sicily, Italy) where there are two fields wells (Staglio e Bresciana) for abstraction of drinking water. According to twenty years collected data about quality of drawing it is necessary to determine the potential vulnerability of the aquifer in order to prevent pollution phenomena of the rich body of water. The groundwater chemical composition of the unconfinated aquifer shows high level of nitrate, sulfide and potassium caused by the frequent use of chemical additives in agriculture. In the investigated aquifer the water discharge, mainly represented by pumping to irrigation and civil use, is more or less 15% higher then mean annual recharge. This study consequently is the starting point for the definition of hazardousness and pollution risk, as well as for a correct water management policy. Key-words: hydrogeology; multiaquifer; groundwater mining; vulnerability; sustainability.

Introduction The present work is intended to describe the groundwater lowering in the Piana of Castelvetrano and Campobello di Mazara (Western Sicily) and to identify the basic quality of the groundwaters (Civita M, et al.,1993), as a contribution to a correct estimation of the potentially available resources for different uses (Legislative Decree 152/99). The groundwaters resources in the considered zone, are intended for civil and irrigation use; consequently, in the last twenty years, it is occurred a lowering of the piezometric level, also accentuated by the succession of hydrogeologic years with few rainfalls. So, in this area, the intense exploitation of aquifers and the wide use of fertilizers may cause a degradation of their qualitative and quantitative features (Affuso A.M.G.et al.,1999). Besides this, if we add the bad management of the water resources and the more and more growing diffusion of productive activities which represent potential hazardous factors (Civita M et al., 1995), it is clear how important is to consider the hydrogeologic hazard, especially, in a zone where dryness is particularly frequent.

Geological setting The area chosen for this study includes the Piana di Castelvetrano and Campobello di Mazara (Western Sicily). The Piana, extended between the River Delia in the west and the River in the east, sloping down softly to south with a slight incline (10o-15o) has a course approximately southwest-northeast and an average altitude of 100 a.m.s.l. The morphology of the zone, quite regular, represents the result both of the action of the quaternary sea and of that one of the rivers which have an incidence more or less deep on it, and of the other exogenous agents which have acted selectively on the different lithological types. The geological features are represented by a series of quaternary marine terraces (D’Angelo et al., 1992,2001) covering a neogenic sequence (Bommarito S.,1984). These terrains are characterized by clayey deposits of Terravecchia Formation, on which the Messinian evaporitics terrains lean on uncorfomably, passing, in their turn, on the upper part, to the pelagic and detritus-organogenic plioquaternary deposits.

Water bodies protection and Ecohydrology 1

BALWOIS 2004 Ohrid, FY Republic of Macedonia, 25-29 May 2004

Particularly, the stratigraphy of the studied area is characterized, from the lower part upward: Terravecchia Formation (Upper Tortonian – Lower Messinian): clayey-marley and clayey- sandy terrigeneous deposits, containing sandy-conglomeratic levels; Gessoso Solfifera Formation (Upper Messinian):