Physico-chemical behaviour of underground waters after the october 1, 1995 Dinar earthquake, SW Turkey

On the evening of October 1, 1995, a MS46.1 earthquake destroyed the city of Dinar, SW Turkey. Within 48 hours after the main shock, a team of the German Earthquake Task Force arrived in the area to investigate possible earthquake-related changes in the physico-chemical composition of shallow and deep groundwaters. A mapping was performed to characterise different groundwater types and a continuously monitoring station was installed within the geothermal field of Afyon. Repeated measurements, performed 1, 6, 12 and 18 months after the event, reveal post-seismic changes in water discharge, water temperature, and conductivity. We will focus on the changes of spring water discharge observed in the vicinity of the epicentre. In the first month after the earthquake the groundwater discharge increased at springs located within the down-thrown block, whereas a slight decrease was observed at sites on the hanging wall

The impact of hydrological conditions on salinisation and nitrate concentration in the coastal Velez River aquifer (southern Spain)

This study reports the impact of hydrological conditions on salinisation and nitrate concentrations of a coastal aquifer located at the Mediterranean Sea, southern Spain. Eighty-two samples of ground- and surface water taken during two extreme hydrological events between 1994 and 1996 at 25 different wells were evaluated with regard to hydrochemistry, focusing on nitrate concentrations and salinisation, which constitute the main hazard of this aquifer. Furthermore, hydrochemical data were analysed by principal component analysis (PCA). Additionally, in 2007 13 ground- and surface water samples taken at 12 different locations were analysed for stable isotopes of D/18O, and one sample was analysed for 15N. Since 1993 until present saltwater intrusion was observed only during dry hydrological conditions in 1994; it showed an irregular salinisation pattern probably related to locally elevated hydraulic conductivities. Nitrate concentrations increase significantly during wet hydrologic conditions owing to uptake of nitrate by rising groundwater. Stable isotopes of groundwater reveal an Atlantic origin of the precipitation that recharges the aquifer and a minor amount of groundwater recharge by the water coming from the La Viñuela reservoir, which is used for irrigation over the aquifer. 15N isotopes point to a considerable input of nitrates derived from organic fertilisers.Institute of Geological Sciences, Freie Universitát Berlin, AlemaniaInstituto del Agua, Universidad de Granada, EspañaUnidad de Murcia, Instituto Geológico y Minero de España, EspañaDepartmento de Geología, Universidad de Málaga, EspañaAlfred Wegener Institute, Alemani

Deep geothermal groundwater flow in the Seferihisar-Balcova area, Turkey: results from transient numerical simulations of coupled fluid flow and heat transport processes

The Seferihisar-Balcova Geothermal system (SBG) is characterized by complex temperature and hydrochemical anomalies. Previous geophysical and hydrochemical investigations suggest that hydrothermal convection in the faulted areas of the SBG and recharge flow from the Horst may be responsible for the observed patterns. A numerical model of coupled fluid flow and heat transport processes has been built in order to study the possible fluid dynamics of deep geothermal groundwater flow in the SBG. The results support the hypothesis derived from interpreted data. The simulated scenarios provide a better understanding of the geophysical conditions under which the different fluid dynamics develop. When recharge processes are weak, the convective patterns in the faults can expand to surrounding reservoir units or below the seafloor. These fault-induced drag forces can cause natural seawater intrusion. In the Melange of the Seferihisar Horst, the regional flow is modified by buoyant-driven flow focused in the series of vertical faults. As a result, the main groundwater divide can shift. Sealing caprocks prevent fault-induced cells from being overwhelmed by vigorous regional flow. In this case, over-pressured, blind geothermal reservoirs form below the caprocks. Transient results showed that the front of rising hot waters in faults is unstable: the tip of the hydrothermal plumes can split and lead to periodical temperature oscillations. This phenomenon known as Taylor-Saffman fingering has been described in mid-ocean ridge hydrothermal systems. Our findings suggest that this type of thermal pulsing can also develop in active, faulted geothermal systems. To some extent, the role of an impervious fault core on the flow patterns has been investigated. Although it is not possible to reproduce basin-scale transport processes, this first attempt to model deep groundwater geothermal flow in the SBG qualitatively supported the interpreted data and described the different fluid dynamics of the basin

Origin and dynamics of groundwater salinity in the alluvial plains of the western Dehli and adjacent territories of Haryana State, India

International audienceGroundwater salinity is a widespread problem and a challenge to water resources management. It is an increasing concern in the alluvial plains of Delhi and neighbouring Haryana state as well as a risk for agricultural production water supply and sustainable development. This study aims to identify potential sources of dissolved salts and the driving mechanisms of salinity ingress in the shallow aquifer. It combines a comprehensive review of environmental conditions and the analysis of groundwater samples from 25 sampling points. Major ions are analysed to describe the composition and distribution of saline groundwater and dissolution/precipitation dynamics. Density stratification and local upconing of saline waters were identified by multilevel monitoring and temperature logging. Bromide-chloride ratios hold information on the formation of saline waters, and nitrate is used as an indicator for anthropogenic influences. In addition, stable isotope analysis helps to identify evaporation and to better understand recharge processes and mixing dynamics in the study region. The results lead to the conclusion that surface water and groundwater influx into the poorly drained semiarid basin naturally results in the accumulation of salts in soil, sediments and groundwater. Human-induced changes of environmental conditions, especially the implementation of traditional canal and modern groundwater irrigation, have augmented evapotranspiration and led to waterlogging in large areas. In addition, water-level fluctuations and perturbation of the natural hydraulic equilibrium favour the mobilisation of salts from salt stores in the unsaturated zone and deeper aquifer sections. The holistic approach of this study demonstrates the importance of various salinity mechanisms and provides new insights into the interference of natural and anthropogenic influences. Copyright (c) 2011 John Wiley & Sons, Ltd