Turkey is an area of complex geology with active tectonics and high geothermal potential. Especially, the western part of Turkey is a region of abundant geothermal activity. Faults accommodating the deep circulation of hydrothermal fluids of meteoric origin are the primary means by which of geothermal systems are controlled in this region. Many of the thermal activities are related to the improved dilation on the~E-W-strikes of the graben faults. This situation serves as a suitable environment for the presence of high levels of arsenic in geothermal water resources. The highest concentrations of naturally occurring aqueous arsenic (As) are found in certain types of geothermal waters, generally those related to major graben faults. In this regard, high arsenic concentrations in geothermal resources have been detected in Western Turkey, including but not limited to Biga Peninsulla, Gediz Graben, Kucuk, and Buyuk Menderes Graben with values ranging from 1 to 1419 ppb in geothermal fluids. The thermal waters have surface temperatures of up to 100°C and reservoir temperatures range from 150 to 248°C in the Menderes Graben, from 120 to 287°C in the Gediz Graben, and from 153 to 174°C in Biga Peninsula. Hydrogeochemically, the Menderes graben and Gediz Graben thermal waters are of the Na-HCO 3 , Ca-HCO 3, and Na-SO 4 types, whereas some geothermal fluids such as those of Tuzla and Kestanbol in the Biga Peninsula, Çeşme, and Urla are of the Na-Cl type.
Many agricultural production areas worldwide are characterized by high variability of water supply conditions, or simply lack of water, creating a dependence on irrigation since Neolithic times. The aim of this paper is to provide an overview of the evolution of irrigation of agricultural lands worldwide, based on bibliographical research focusing on ancient water management techniques and ingenious irrigation practices and their associated land management practices. In ancient Egypt, regular flooding by the Nile River meant that early agriculture probably consisted of planting seeds in soils that had been recently covered and fertilized with floodwater and silt deposits. On the other hand, in arid and semi-arid regions farmers made use of perennial springs and seasonal runoff under circumstances altogether different from the river civilizations of Mesopotamia, Egypt, India, and early dynasties in China. We review irrigation practices in all major irrigation regions through the centuries. Emphasis is given to the Bronze Age civilizations (Minoans, Egyptians, and Indus valley), pre-Columbian, civilizations from the historic times (e.g., Chinese, Hellenic, and Roman), late-Columbians (e.g., Aztecs and Incas) and Byzantines, as well as to Ottomans and Arabs. The implications and impacts of irrigation techniques on modern management of water resources, as well as on irrigated agriculture, are also considered and discussed. Finally, some current major agricultural water management challenges are outlined, concluding that ancient practices could be adapted to cope with present challenges in irrigated agriculture for increasing productivity and sustainability.
a b s t r a c tTuzla is an active geothermal area located in northwestern Turkey, 80 km south of the city of Canakkale and 5 km from the Aegean Coast. The geothermal brine from this area, which is dominated by NaCl, has a typical temperature of 173• C. Rapid withdrawal of fluid to ambient surface conditions during sampling causes precipitation of various compounds known as scaling. Scaling is one of the important problems in Tuzla geothermal system that reduces the efficiency of the geothermal power plant and causes economical loss. The aim of this study was to determine the type of scaling as a first step towards preventing its formation. The scales formed in the geothermal system were divided into two groups according to location: the ones that formed in downhole and the ones that accumulated along the surface pipeline. Both scales were examined in terms of their elemental composition, structure and morphology using XRF, XRD, and SEM, respectively. The former was found to be mainly composed of PbS (Galena) and CaCO 3 (aragonite or calcite). In contrast, the latter was heterogeneous in nature and consisted of mainly saponite like amorphous structure along with submicrometer-sized amorphous silica particles, layered double magnesium and iron hydroxide, and NaCl.
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