Impacts due to over-abstraction
Water availability problems occur when the demand for water exceeds the amount available during a certain period.
They happen frequently in areas with low rainfall and high population density, and in areas with intensive agricultural or industrial activity. Apart from causing problems by providing water to users, over-exploitation of water has led to the drying-out of water courses and wetland areas in Europe as well as salt-water intrusion in aquifers.
Groundwater overexploitation and saline intrusion
Source: EEA 2003/ EEA dataservice
In many areas of Europe, groundwater is the dominant source of freshwater. In a number of places water is being pumped from beneath the ground faster than it is being replenished through rainfall. The result is sinking water tables, empty wells, higher pumping costs and, in coastal areas, the intrusion of saltwater from the sea which degrades the groundwater.
Saline intrusion is widespread along the Mediterranean coastlines of Italy, Spain and Turkey, where the demands of tourist resorts are the major cause of over-abstraction. In Malta, most groundwater can no longer be used for domestic consumption or irrigation because of saline intrusion, and the country has resorted to desalination. Intrusion of saline water due to excessive extraction of water is also a problem in northern countries.
Sinking water tables can also make rivers less reliable, since many river flows are maintained in the dry season by springs that dry up when water tables fall. Groundwater also helps sustain surface reservoirs of water such as lakes and wetlands that are often highly productive ecosystems and resources for tourism as well as leisure activities. These, too, are threatened by over-abstraction of groundwater.
Irrigation is the main cause of groundwater overexploitation in agricultural areas. Examples include the Greek Argolid plain of eastern Peloponnesus where it is common to find boreholes 400m deep contaminated by sea-water intrusion. In Italy, overexploitation of the Po River in the region of the Milan aquifer has led to a 25m (even up to 40 m) decrease in groundwater levels over the last 80 years (Blue Plan, 2005). In Spain, more than half of the abstracted groundwater volume is obtained from areas facing overexploitation problems (MIMAM, 2000).