Evidence and implications of extensive groundwater overdraft-induced land subsidence in Greece

Abstract

Groundwater resources have been over-utilized in Greece with water table drops of tens of meters becoming common the last thirty years and tens of thousands of wells developed without reference to the EU Water Framework Directive. This has led to extensive land subsidence with rates ranging from 1 to over 4 inches per year and becoming apparent throughout the country. The principal subsidence mechanism appears to be that of consolidation with aquifer re-organization and drainage and compaction of aquitards. Drainage of the extensive wetlands in Greece undertaken from the 1920s to 1960s, for control of malaria and flooding, and to increase the cultivated lands has also led to oxidation of the rich peat soils and to land subsidence of meters. In addition to subsidence occurrences on mainland Greece, recent DInSAR results for the island of Crete indicated that the productive Messara Plain is subsiding at a rate of at least 2 cm/yr as a result of the 40-meter groundwater drop over the last 20 years. Groundwater resources’ depletion and widespread land subsidence pose serious infrastructure threats for the country. In order to mitigate the situation extensive water diversion and aquifer replenishment projects, in conjunction with water savings and crop selection measures need to be implemented.