C. Serdar Bayari

Determination of the origin of the waters of Köyceǧiz Lake, Turkey

Abstract The Koyceǧiz Lake in south-western Turkey is a meromictic lake, comprised of waters of both thermal and cold-karstic origin. The lake is principally fed from surface flow, ground water recharge from alluvium and thermal discharges located at the bottom of the lake. As indicated by physical and chemical observations, the lake is composed of two hydrochemically distinct water layers. There is a transition zone between these two layers at a depth of approximately 10 m. The bottom layer, which contains more mineralized water, is recognized easily by the smell of hydrogen sulfide gas. A decrease in pH and dissolved oxygen and an increase in specific conductivity and ionic constituents are observed at the transition zone in depth profiles at all measurement sites throughout the year. The isotopic compositions of the representative observation points widely scatter and indicate the mixing of thermal and cold-karstic waters. As indicated by satellite imagery data, the morphology of the lake shores are primarily controlled by structural elements, which are mostly normal faults. Echo-sounding profiles point out that some of the fault lines, along which the lake bottom springs seem to be located, extend through the lake bottom. Current velocity observations also indicate possible sites of thermal ground water discharges located at the lake bottom.

Effects of the North Atlantic Oscillation and groundwater use on the contraction of Sultansazligi Wetland, Turkey

The Sultansazligi Wetland, an internationally important aquatic site in Turkey, has suffered from a severe contraction since the early 1990s. To determine the factors affecting contraction, temporal variations of climatic and hydrogeologic variables have been investigated. Both the long-term climate change and the increasing surface and groundwater use are found to be responsible. Hydrologic analyses reveal an apparent correlation between increasing use of water resources and contraction in the wetland. Particularly, increasing use of groundwater and complete capture of springs and effluent streams once feeding the wetland are found to be the prime factors. Furthermore, a strong coherence is found between the temporal trend of the North Atlantic Oscillation and local precipitation, which is the main source of the basin’s water excess and supplies the wetland. Future existence of the wetland depends on the application of thrifty water-use polices in irrigation.RésuméLe Sultansazligi Wetland, un site humide Turc d’importance internationale, a subi d’importantes réductions de surface depuis le début des années 1990. Pour déterminer les facteurs de la réduction de la zone humide, on a étudié les fluctuations du climat et des variables hydrogéologiques. On a trouvé qu’à la fois le changement climatique à long terme et l’accroissement de l’utilisation du sol et de l’eau souterraine se révèlent comme étant responsables. Les analyses hydrologiques révèlent une apparente corrélation entre l’utilisation croissante des ressources en eau et la réduction de surface de la zone humide. En particulier, l’utilisation croissante de l’eau souterraine et le captage intégral des sources et des cours d’eau ayant autrefois alimenté la zone humide sont reconnus comme en étant les facteurs principaux. De plus, on trouve une forte corrélation entre la tendance de l’Oscillation Nord Atlantique et les précipitations locales, principales source d’eau excédentaire du bassin alimentant la zone humide. L’existence future de la zone humide dépend de l’application à l’irrigation d’une police de l’eau économe.ResumenEl humedal Sultansazligi, un sitio acuático internacionalmente importante en Turquía, ha sufrido una severa contracción desde los primeros años de la década del 90. Para determinar los factores que afectan la contracción se han investigado las variaciones climáticas temporales e hidrogeológicas. Se encontró que tanto el cambio climático a largo plazo como el uso creciente de agua subterránea y superficial son los responsables. Los análisis hidrogeológicos revelan una correlación aparente entre el incremento en el uso de los recursos de agua y la contracción en el humedal. En particular, se encontró que los principales factores son el incremento del uso de agua subterránea y la captura completa de los manantiales y corrientes efluentes que alguna vez alimentaron subterráneamente al humedal Más aún, se encontró una fuerte coherencia entre la tendencia temporal de la oscilación del Atlántico Norte y las precipitaciones locales, que es el origen principal de los excesos de agua de la cuenca y abastecimiento del humedal. La existencia futura del humedal depende de la aplicación de políticas cuidadosas en el uso del agua para irrigación.摘要Sultansazligi 湿地是土耳其境内具有国际性意义的水域,但从 20 世纪 90 年代开始退化非常严重。为了分析影响退化的原因,我们调查了研究区内气候和水文地质变量随时间变化的特征。结果表明,长期的气候变化和地表地下水利用的增加都是相应的原因。水文分析显示水资源利用的增加与湿地的退化密切相关。尤其是地下水利用量的增加和原本补给湿地的泉水与河流的全面利用是首要原因。本地降水既是该流域内过量水的来源,也是湿地的补给源,进一步研究发现,本地降水与北大西洋涛动的变化趋势一致。湿地的未来取决于节约灌溉水政的实施。ResumoA zona húmida de Sultansazligi, um sítio aquático importante a nível internacional na Turquia, sofreu uma forte contração desde o início da década de 1990. Tendo em vista determinar os factores que afetam a contração, investigaram-se as variações temporais de variáveis climáticas e hidrogeológicas. Verificou-se que, tanto a alteração climática de longo termo, como a utilização crescente de águas superficiais e de águas subterrâneas foram responsáveis por esse fato. A análise hidrológica revela uma aparente correlação entre o uso crescente dos recursos hídricos e a contração da zona húmida. Em particular, verifica-se que os factores principais responsáveis por este processo são o uso crescente de águas subterrâneas e a captação completa das nascentes e dos cursos de água efluentes que alimentavam a zona húmida. Além disso, encontra-se uma forte coerência entre a tendência temporal da Oscilação do Atlântico Norte e a precipitação local, que é a principal origem de excedente hídrico da bacia e abastece a zona húmida. A existência futura da zona húmida depende da aplicação de políticas parcimoniosas de utilização da água na rega.ÖzTürkiye’deki uluslararası öneme sahip sucul ekosistemlerden Sultansazlığı sulak alanı 1990’lardan günümüze önemli düzeyde küçülmüştür. Küçülmeye neden olan etkenlerin belirlenmesi için iklimsel ve hidrojeolojik değişkenlerin zamansal değişimi incelenmiştir. Uzun sureli iklim değişimi ile yüzey ve yeraltısularının artan kullanımının küçülme üzerinde etkili olduğu belirlenmiştir. Hidrolojik analizler su kaynaklarının artan kullanımı ile sulak alandaki küçülme arasında belirgin bir korelasyon olduğunu göstermiştir. Özellikle, bir zamanlar sulak alanı besleyen kaynakların ve akarsuların tamamen sulamaya tahsis edilmesinin ve artan yeraltısuyu kullanımının küçülme üzerinde etkili temel faktörler oldukları belirlenmiştir. Bunun ötesinde, sulak alanı besleyen ve havzadaki su fazlasının başlıca kaynağı olan yağış ile Kuzey Atlantik Salınımının zamansal eğilimleri arasında güçlü bir ilişki bulunmuştur. Sulak alanın gelecekteki devamlılığı tutumlu sulama politikalarının uygulanmasına bağlıdır.

Geodynamic Control of Hypogene Karst Development in Central Anatolia, Turkey

Hypogene karst development in central Anatolia, Turkey is represented by unique collapse dolines (obruks) developed mainly in Neogene lacustrine limestone formations. Many of these obruks are located in two separate rectilinear zones, one of which appears to mark the suture zone between Tauride-Anatolian and Sakarya Zone tectonic blocks of the Anatolian plate. The other zone coincides with the alignment of three dormant volcanoes. Formation of obruks seems to be associated with upwelling of carbon dioxide released from deep-rooted igneous activity sources along these zones since Late Miocene. Formation of obruks still continues today, whereas the size of recent collapses is much smaller than ancient examples probably due to weakening volcanism. Recent obruk formations are observed in an area where the youngest volcanic activity seems to have occurred. Frequency of obruk formation increased in recent years because of the groundwater’s accelerating piezometric head decline. The stable carbon and noble gas isotope data previously obtained from regional groundwater samples suggested both crustal and mantle sources for the carbon dioxide required for obruk formation. It seems likely that many of the large-scale karst cavity-collapse structures in the world are linked with excessive carbon dioxide release from mantle in orogenic plateaus like central Anatolia.