Diachronic evolution of water supply in the Eastern Mediterranean
4.4 DISCUSSION AND CONCLUSIONS
The socioeconomic development of a region is usually associated with the availability of water resources.
Mediterranean countries are characterised by semi-arid climate conditions. After the last glacial period ended 12,000 years ago, climate changes were small and variable from region to region. Many areas today are facing the same problem of water shortage as they did in the past. An integrated strategy for water resources management, aimed at the mitigation of the impacts of water shortage, is therefore necessary at a local and regional scale. The ancient technologies and water management practices are a useful tool for current-day engineers.
At the earliest stage, people performed all their activities near rivers and streams and surface water was the main source of water supply. However, the surface water resources were influenced by the seasonal precipitation. For this reason people started to explore groundwater. Springs are the natural emergence of groundwater. Thus, many springs were used directly for water supply.
The ancient peoples devised wonderful hydraulic works, including tunnels, wells, aqueducts and so on, to supply the cities with water. These works are located in areas which today are faced with water supply problems. The Roman period is characterised by the construction of admirable aqueducts that carried water to the cities from a long distance. In the Byzantine period, the construction of aqueducts was abandoned and tanks and cisterns were constructed in order to collect rain water. The Ottoman period is characterised by the construction of qanats and the exploitation of springs. In the case of extended dry periods, the water supply was assisted by the exploitation of groundwater from shallow aquifers.
The greatest achievement in groundwater exploitation by ancient peoples in the Near and Middle East was in the construction of qanats. Many qanats in Greece were constructed during the Ottoman period;
the largest in total length (tunnel and transfer conduit) is that of Chortiati at 20 km. The qanats consist of one underground tunnel and a sequence of shafts (wells) that convey water from shallow aquifers in highlands by gravity to lowlands and some of them are still in use today. In addition, the aqueducts consisting of channels, tunnels and water bridges, as well as small dams, cisterns and so on, are admirable hydraulic works of ancient people to transfer and store water. The oldest aqueduct in Greece is the tunnel of Eupalinos in Samos, which is one of the greatest engineering achievements of ancient times, representing the peak of ancient hydraulic technology.
Given the current climatic conditions, the period of dryness in Mediterranean countries ranges between 3 and 6 months. Water consumption has doubled during the last four decades. Agricultural demand for irrigation water is a major share of the total water demand in Mediterranean countries (60–85%). It should be mentioned that during the dry years the abstraction rate for agricultural purposes increases (up to 25%), because of the prolonged irrigation period, the land under irrigation and the amount of water applied per irrigated area (Chartzoulakis et al.2001). Demand for domestic water also increases during drier periods. Droughts also contribute to the quality deterioration of surface water because they cause a decline in river and stream discharge (EEA, 2007). It is pointed out that coastal aquifer systems in Mediterranean countries are already threatened by seawater intrusion due to human activities and geological conditions.
The aforementioned works demonstrate that the ancient people in Mediterranean countries had an outstanding engineering knowledge of water supply. The study of these works will help solve the current water problem in many areas. The horizontal works (tunnels, galleries, and qanats) have the advantage of avoiding seawater intrusion problems in coastal areas. Furthermore, these water supply works have the advantages of saving energy (no pumping water) and reducing water losses from evaporation. Finally, these works are effective for water harvesting in arid or semi-arid areas of Mediterranean countries.
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