Modélisation des flux et de la qualité des eaux dans les systèmes karstiques à l'aide des méthodes "soft computing" (réseaux de neurones, logique floue)

Karstic aquifers present a great extension throughout the world (12 % of the emerged grounds) and in particular in countries around the Mediterranean sea (from 20 to 90 % of the surface of the Mediterranean countries). These aquifers represent important groundwater potentialities. In both countries (France and Turkey), these karstic aquifers are exploited for drinking water supply and other economic activities (agriculture, pisciculture,...) and constitute the single water resource in certain areas of these countries. The role of these karstic hydrosystems in the social and economical context of some areas is extremely crucial. These aquifers are very vulnerable to contaminations and are overexploited, taking into account the increase in water requirements. Karstic aquifers are very complex and show very particular characteristics (strong heterogeneity, anisotropy, discontinuity of the medium, hierarchization of the flows), which make difficult any classical approach of identification of these systems and management of their water resources. The difficulty of modeling comes owing to the fact that these karstic systems are highly non-linear and are little adapted to the classical methods of identification (flow and transport modeling based on Darcy law). Soft computing methods (Artificial neural networks and fuzzy logic) are playing a key role in the modelling of complex and nonlinear problems. The uncertainty associated with the data, the immense size of the data to deal with, the diversity of the data type and the associated scales are important factors to rely on unconventional mathematical tools such as soft computing. In this thesis, the three pilot experimental sites are: the karst of La Rochefoucauld in France which is used in particular for the supply of the regional capital Angouleme; Orbe karstic spring which supplies the rural city of Arette (Southwestern France) and the karst of Safranbolu in Turkey which supplies the town of Safranbolu. The principal objective of this work is to test the ability of soft computing methods for modeling of complex karstic systems and predicting the discharge rates and quality of water at the outlets of these systems. The results show the ability of Soft computing method to model these highly non linear systems. All the modelling work was carried out using the Matlab programming environment.POITIERS-BU Sciences (861942102) / SudocSudocFranceF

Evolution of noble gas and water isotopes along the regional groundwater flow path of the Konya Closed Basin, Turkey

Noble gas and water isotope compositions of regional groundwater were investigated along two transects in the Konya Closed Basin (KCB) of central Turkey. According to the 3He/4He versus Ne/He plot of samples, crust (up to 86%) and mantle (up to 26%) appear to be the primary and secondary sources of dissolved He in groundwater, respectively. After the beginning of both transects where the flow domain is confined, both 3He and 4He accumulate steadily in groundwater. Thereafter, the intermediate recharge from the surface in the unconfined part of regional flow system disrupts the steady accumulation trend of 3He and 4He. Effect of intermediate recharge on regional groundwater is also indicated by the spatial variations in specific conductance, temperature, water isotopes, and tritium signals. At the last part of the flow domain where the system becomes confined again 3He and 4He start to accumulate in the eastern transect whereas they continue to decline in the western transect probably because of degassing to atmosphere through thinner confining unit. The 4He accumulation rates based on radiocarbon ages and 4He concentrations along both transects between the mountain flank and Obruk Plateau are in agreement with literature values but differ from each other. The accumulation rate along the eastern and western transects are 4.93 × 10-11 cm3 STP/g•year and 1.99 × 10-10 cm3 STP/g•year, respectively. These values reveal that the 4He accumulation rates may differ at least four times at different parts of a single aquifer, which are located 30 to 60 km apart. It is understood that any groundwater age-dating attempt by 4He requires a firm pre-assessment of spatial 4He accumulation rates. He isotope signal in the groundwater of KCB proves the mantle and/or crustal gas input into the carbonate aquifer in which an on-going hypogenic karst development has been suspected

Evolution of noble gas and water isotopes along the regional groundwater flow path of the Konya Closed Basin, Turkey

Noble gas and water isotope compositions of regional groundwater were investigated along two transects in the Konya Closed Basin (KCB) of central Turkey. According to the 3He/4He versus Ne/He plot of samples, crust (up to 86%) and mantle (up to 26%) appear to be the primary and secondary sources of dissolved He in groundwater, respectively. After the beginning of both transects where the flow domain is confined, both 3He and 4He accumulate steadily in groundwater. Thereafter, the intermediate recharge from the surface in the unconfined part of regional flow system disrupts the steady accumulation trend of 3He and 4He. Effect of intermediate recharge on regional groundwater is also indicated by the spatial variations in specific conductance, temperature, water isotopes, and tritium signals. At the last part of the flow domain where the system becomes confined again 3He and 4He start to accumulate in the eastern transect whereas they continue to decline in the western transect probably because of degassing to atmosphere through thinner confining unit. The 4He accumulation rates based on radiocarbon ages and 4He concentrations along both transects between the mountain flank and Obruk Plateau are in agreement with literature values but differ from each other. The accumulation rate along the eastern and western transects are 4.93 × 10-11 cm3 STP/g•year and 1.99 × 10-10 cm3 STP/g•year, respectively. These values reveal that the 4He accumulation rates may differ at least four times at different parts of a single aquifer, which are located 30 to 60 km apart. It is understood that any groundwater age-dating attempt by 4He requires a firm pre-assessment of spatial 4He accumulation rates. He isotope signal in the groundwater of KCB proves the mantle and/or crustal gas input into the carbonate aquifer in which an on-going hypogenic karst development has been suspected

ESR and 230Th/234U dating of speleothems from Aladaǧlar Mountain Range (AMR) in Turkey

Electron spin resonance (ESR) and Th/U ages of speleothem samples collected from karstic caves located around 3000m elevation in the Aladaǧlar Mountain Range (AMR), south-central Turkey, were determined in order to provide new insight and information regarding late Pleistocene climate. ESR ages were validated with the Th/U ages of test samples. The ESR ages of 21 different layers of six speleothem samples were found to range mostly between about 59 and 4ka, which cover the Marine Oxygen Isotope Stages (MIS) MIS 3 to MIS 1. Among all, only six layers appear to have deposited during MIS 8 and 5. Most of the samples dated were deposited during the late glacial stage (MIS 2). It appears that a cooler climate with a perennial and steady recharge was more conducive to speleothem development rather than a warmer climate with seasonal recharge in the AMR during the late Quaternary. This argument supports previous findings that suggest a two -fold increase in last glacial maximum mean precipitation in Turkey with respect to the present value

Morphological abnormalities in benthic foraminifers of the Antalya coast

Many researchers report abnormal test morphologies in benthic foraminifers and some suggest that anthropogenic pollution may be one of the Causes for these anomalies. Sonic species are even used as bioindicators of anthropogenic pollution. However, environmental stress may be exerted by natural factors also, such as hypersalinity, periodical acidification and strong hydrodynamics. We observed large populations of morphologically abnormal foraminifer individuals in 227 recent sediment samples on the southwestern coast of Antalya (Turkey). In 117 Of Our samples we found morphologically abnormal Textularia bocki Hoglund individuals. The proportion of abnormal individuals to normal ones within a population is 3.2%. We also found morphologically abnormal individuals of Peneroplis arietinus Batsch, P. pernisits (Forskal), P. wplanatus (Fichtel and Moll), Amphisorus hemprichii Ehrenberg, Sorites orbiculus Ehrenberg, S. variabilis Lacroix and Spiroloculina cf. S. angulata d'Orbigny in 87 of our sediment samples. The abundance and large sizes of these abnormal individuals are significant. There is no industrial plant near the study area and this region is not a popular tourist attraction. Thus, anthropogenic waste cannot be regarded as an important cause for unhealthy foraminifers in this region. There are frequent freshwater springs along the coast around Kalkan, Kas and eastern Kekova. Seasonal discharge front submarine caves also contributes freshwater to the sea ranging between 12% and 50%. Radioactivity levels and heavy metal concentrations in these submarine discharges are insignificant. However, we see a correlation between the abundance of abnormal individuals and the locations of caves and freshwater springs in the region. Our results suggest that rapid changes in ecological parameters related to submarine groundwater discharge may be responsible for morphological anomalies in foraminiferal genera and species