Along the coastlines of certain countries , such as Libya and Israel , population growth has led to over-population which has caused the lowering of water table and the subsequent contamination of the groundwater with saltwater from the sea ( saline intrusions ) . Along the coastlines of certain countries , such as Libya and Israel , population growth has led to over-population , which has caused the lowering of water table and the subsequent contamination of the groundwater with saltwater from the sea ( saline intrusions ) .