Long-term changes of water and salinity management in Lower Seyhan Plain, Turkey

A Long-term change of shallow water table fluctuation patterns was assessed for a large-scale irrigation district which extends over an alluvial plain in Turkey in the Eastern Mediterranean. Over the last 20 years the water table which was previously characterized by large fluctuations and acute peaks, became flat and lost seasonality as a consequences of increases in the amount and duration of irrigation and of improvements in drainage. Salinity level of shallow water table also decreased over this twenty year period. Analysis by the Irrigation Management Performance Assessment Model suggested that leakage from canals was responsible for keeping the groundwater level high. Open drainage and sub-surface drainage were constantly functioning for drainage of excessive water. While many parts of the world suffer from increasing salinity problems associated with over-irrigation, Lower Seyhan Plain seems to be a fortunate exception case because i) introduction of summer irrigation to Mediterranean Climate with winter precipitation kept soil water flux always downward, ii) good drainage networks quickly carried away surplus water and iii) irrigation water supplied from upstream had low salt content and there was no hazard for secondary salinization.