Studies on different kinds of salinisation in the groundwaters of the Ionian coastal plain of the Basilicata region.

The research by now carried out on the Ionian coastal plain of the Basilicata region allowed defining, for the first time, that the coastal plain is constituted by a hydrogeological system formed by three kinds of aquifers, well confined at the bottom by the blue clay basement. The tectonic evolution of the region affected the clay basement during its sedimentation, followed by the erosion by five rivers and subsequent deposition of alluvial sediments. As a consequence of faulting and fissuring, and following sea level changes, the hydrogeological system and the basement have been subject in geological times to seawater intrusion episodes. Mainly the construction of 17 dams and small barrages for water storage, together with the diversion on the five main rivers or in their basins, but also the land reclamation during the 20th century and practices, deeply modified the hydrology of the coastal plain by strongly reducing natural superficial flow and by changing periods and areas of recharge. The geomorphologic features of the coastal border, the recent sea level changes and the human activities, added to the above complexity, brought forth the conditions in the hydrogeological system for the existence of a number of salinisation sources whose effects somewhere overlap: salt water from superficial intrusion of seawater in the rear dune ponds or in the river mouths, salt water from overexploited alluvial aquifers, salt diffusion from interstitial water of the over-consolidated marine blue clays, solution of sulphates from evaporite deposits and salt concentration due to recycling of irrigation water. Specific situations of salt concentration from human activities have been also recognized in some sites. The high amount of water used for irrigation and, in the dry seasons, the overexploitation of groundwaters, act, in the different environments, favouring or limiting the salinisation. A detailed study, which was carried out on the base of stratigraphic data, temperature and conductivity logs, and chemical analyses of groundwaters, contributed to discriminate the different salinisation sources.