Akdeniz Iklim Kusaglnda, Sulamadan Donen Sularln Sulamada Kullanllmaslnln Taban Suyu Kalitesi ve Derinligi Uzerine Etkilerinin Arastlrllmasl: Asagl Seyhan Ovasl Yemisli Sulama Sahasl Ornegi




This study was conducted in Yemisli irrigation area of the Lower Seyhan Plain, the south of Turkey, Adana. Overall, farmers in the study area use IRFs for irrigation with practicing surface irrigation methods characterized by low irrigation efficiency. Objective of this study was to examine the potential problems regarding groundwater (GW) quality and quantity that may be caused by using IRFs having poor quality in irrigation. In this context, GW depths and qualities were observed in 55 drainage observation wells with the depth of 3 m. Observation wells were installed in the study area with an almost homogeneous distribution. Groundwater depth (m) were recorded in winter (February), autumn (April), peak irrigation season (July) and at end of irrigation season (September). Concurrently, with GW depth observations, GW water samples were taken and certain water quality analyzes were performed in the laboratory. In the study, the areal averages of groundwater depth were surprisingly found almost equally (1.14 m) in winter and summer seasons. Areas of severe drainage problems (GD depth <1.0 m) covered more than 27% of the total area in February and July. On the other hand, more than 60% of the total area had a GW depth varying between 1.0 and 1.5 m, indicating severe drainage problem. Areal mean GW salinity, i.e. EC, was found to be greater than 20 dS m(-1). This indicates clearly that average GW salinity is almost equal to the half of salinity value of the Mediterranean Sea. This result indicate that the negative impacts of low topography and insufficient drainage with pumping on GW quality and quantity are incontrovertible in the research area. More than 90% of the area has EC values greater than 5 dS m(-1), in terms of drainage engineering principles, known as a threshold value. Furthermore, average groundwater SAR values were found to be above 13 (meq L-1)(0.5) which is considered as a critical value for sodicity hazard. Research findings have clearly revealed that the use of IRFs of inferior quality has had substantial negative impacts on GW quality and quantity. In order to mitigate the problems that have arisen in the study area, it is essential that drainage pumping units should be run accordingly for ensuring efficient drainage that winter rainfalls may wash out the salts accumulated in the root-zone by facilitating water storage function of root-zone. Low topographical situation of the study area should be considered in drainage and open drainage system should be reinforced with tile drains, that irrigation water should be applied with maximum efficiency.