General Characteristics of the Study Area

The study area is located within the boundaries of the districts of Torbali and Bayindir in Izmir Province of Turkey. It is situated about 50 km south of the city of Izmir in western Anatolia (Fig. 25.1). Torbali-Bayindir Plain forms northern portions of Kucuk Menderes River Basin and is located in a wide alluvial zone (Fig. 25.1). Within the plain, Torbali, Bayindir, Caybasi, Ayrancilar, Subasi, and Kuscuburun are main population centers. Agriculture is the main economic activity of the area due to fertile soils and suitable climatic conditions. Both settlements and these agricultural fields supply their drinking and irrigational water demands from wells drilled in the alluvial aquifer.

The plain is located within a graben zone where Mesozoic-aged Menderes metamorphic rocks form the basement and are observed outcropping in the eastern and western parts of the plain [2]. The Menderes metamorphic rocks consist of mica and chlorite schists in their lower levels and dolomitic marble in their upper sections. This formation is widely observed in westerns part of the project area. These schists are nearly impermeable and thus do not supply significant amounts of groundwater. The Neogene Visneli Formation, of limestone and clay-stone, overlies basement rock. This formation is widely observed in northern parts of project area. Finally, Quaternary alluvial layers overlie the basement and Visneli Formation in the study area. The thickness of alluvial layer ranges 30-100 m in the plain.

The evaluation of regional geology revealed that the most important water bearing units in the study area is the alluvial aquifers. The Quaternary surfacial aquifer is composed of the alluvial deposits of Kucuk Menderes River and its tributaries. It is the main water-supplying strata within the study area. This aquifer is divided into two zones according to material properties. Granular material such as sand and gravel are mainly located along the creek beds, while silty sand and clayey material are located elsewhere [3, 4]. This sandy formation is widely used to supply groundwater for domestic agricultural and industrial demands. This aquifer is recharged from surface infiltration and from water seeping along the creek beds. Average conductivity of sandy and silty aquifers are 1.9 x 10-4 and 4.5 x 10-6 m/s, respectively [7].

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