LAND SUBSIDENCE DUE TO EXCESSIVE GROUND WATER WITHDRAWAL. A CASE STUDY FROM STAVROS - FARSALA SITE, WEST THESSALY GREECE
Land subsidence manifestation due to ground-water overexploitation in the Stavros – Farsala site (eastern part of Western Thessaly Basin) has been noticed since 1990. Because of this overexploitation, an excessive drawdown of the ground water level (20 to 40m) was noticed in the various successive aquifers the last decades. The subsidence phenomena resulted to the formation of tensile surface ruptures, which occurred since 2002, affecting roads and buildings. The geological environment of the study area consists of terrestrial Pleistocene deposits containing sands and gravels interbedded with clayey silt to silty clay horizons. These alternations of aquifers (permeable coarse-grained deposits) with aquitards (impermeable to low permeability strata) create a number of successive semi-confined to confined aquifer, initially artesian. This study examines the geological and the hydrogeological conditions of the wider study area, aiming to clarify their relationship with subsidence phenomena and to provide solutions for their suspension. Note that those phenomena are expected to be more incensed during the next few years.