Use of regionalized stormflow coefficients with a view to hydroclimatological hazard mapping

Abstract

An attempt was made to compensate for the lack of long hydrological time series and the lack of information on maximum streamflow in the Alzette River basin (Luxembourg) via the regionalization of stormflow coefficients. Streamflow data recorded since 1995 with a very dense streamgauge network allowed the determination of maximum stormflow coefficients in 18 sub-basins of the Alzette. The stormflow coefficients were then regionalized via stepwise multiple regression analysis for 83 different sub-basins of the Alzette. Combined with 10-year daily rainfall heights (statistical estimation), this regionalization allowed the spatial variability of storm runoff in the Alzette basin to be mapped, thus providing a view of hazard and risk-producing areas, as well as of risk-exposed areas. In a basin with little historical hydrological information this technique can help identify areas where storm runoff reducing measures should be applied from the outset.     

Modeling and simulating earthquake accelerograms using strong-motion data from the Istanbul, Turkey, region

In order to simulate earthquake ground motions for the Instanbul (Turkey) region, acceleration time series from western Turkey are modeled by transforming the series into a stationary one which can be described by an autoregressive moving-average (ARMA) process. The ARMA and other parameters used in the stationary transformation are related to physical parameters (e.g. magnitude, distance to epicenter, depth to hypocenter and duration) via a regression analysis. To create simulations for a given set of physical parameters, the modelling procedure is reversed.     

Estimation of the time-dependent crustal movements of the zmit Earthquake

The 17 August 1999 zmit earthquake significantly deformed the earth's crust in the Marmara Region, especially in the Gölcük–Sapanca Zone, Turkey. It broke a 150-km long segment of the northern branch of North Anatolian Fault Zone. The geodetically determined moment magnitude was M_w=7.5. Global Positioning System (GPS) sites, which are a small subset of the Marmara Continuous GPS Network (MAGNET), and survey sites in the region were studied to estimate coseismic and postseismic deformations, using different methodologies with linear, quadratic and exponential kinematic models. Six GPS epochs for these sites, which were carried out before and after the 17 August 1999 zmit earthquake, were used to define the kinematic models. The quadratic deformation model was also applied to determine the time-dependent crustal movement parameters (velocity and acceleration) of the sites, using the Kalman filter technique. In order to show the differences between the models, the estimated deformation fields on the last epoch were compared. In all models, as expected, the faults near the sites show large coseismic displacements with fault parallel direction, whereas the far sites show small coseismic displacements due to the effects of the zmit earthquake. Each kinematic model, fitted to the epochs after the earthquake, shows different behaviour. While the linear model shows insufficient results, the nonlinear models (quadratic and exponential) give the best fitted to the postseismic deformations. As a result of Kalman filter analysis, the fault near-sites shows significant velocities with fault parallel direction, whereas the far sites have insignificant velocities. All stations have insignificant accelerations in the last epoch.     

The influence of a heavily polluted urban river on the adjacent aquifer systems

 Ankara Creek is often subjected to overflowing of sewage caused by rainfall or direct discharge of raw sewage. Alluvial aquifers adjacent to Ankara Creek and its tributaries have considerable groundwater potential. The present status of groundwater quality is far from drinking water standards. Groundwater contamination in Ankara is suspected to be caused by Ankara Creek which is heavily polluted by raw sewage discharge, surface runoff and other common sources. In order to investigate the influence of heavily polluted Ankara Creek on the groundwater contamination in the adjacent alluvial aquifers, five sampling stations on Ankara Creek and 25 water wells were monitored during 1996. At five different sampling periods, water samples were collected from both surface water and groundwater. Chemical analyses of basic ions, pollution parameters and heavy metals in natural waters were carried out. The organic pollution prevails in Ankara Creek whereas total dissolved solids (TDS) and heavy metal concentrations are considerably low. Starting from the idea that Ankara Creek somewhat influences the groundwater quality and the contaminants in groundwater should attenuate with respect to distance, a series of water wells in a certain area, each having different distance from the creek, were examined using four pollution parameters. It is concluded that Ankara Creek barely influences the aquifer systems in connection. This is attributed to two reasons: rapid attenuation of contaminants due to dilution in groundwater and a blanket of very fine sized materials covering the bottom of Ankara Creek. Received: 28. April 1997 · Accepted: 23. February 1998     

Paleomagnetic results from Northeast Anatolia: remagnetization in Late Cretaceous sandstones and tectonic rotation at the Eastern extension of the Izmir–Ankara–Erzincan suture zone

Paleomagnetic results obtained from Upper Cretaceous sandstones in Northeastern Anatolia demonstrate that the entire area from Erzincan to Kars has been remagnetised. The remagnetisation was acquired before the Middle Eocene collision between the Eastern Pontides and the Arabian Platform because Middle Eocene sandstones carry primary natural remanent magnetisations. The post-folding in situ mean direction of the Upper Cretaceous sandstones is compared with mean directions of younger, Middle Eocene to present rock formations. As a result, a two-stage antagonistic rotation mechanism is proposed. First, the collision between the Pontides and the Taurides between Late Cretaceous and Middle Eocene was associated by clockwise rotation of  ~ 26°. In the second stage between Middle Eocene and Middle Miocene and beyond, counterclockwise rotations up to ~ 52° of the Pontide and Anatolide blocks and clockwise rotations of the Van Block were characterised by regional shortening and westward escape.     

The impact of water resources development projects on water vapor pressure trends in a semi-arid region, Turkey

The aim of this study was to investigate long-term seasonal trends and decadal change patterns of monthly mean water vapor pressure (WVP) observation series at 16 meteorological stations scattered point-wisely over the Southeastern Anatolian Project (GAP) area in Turkey, where large-scale soil and water development projects have been put into practice since the 1970s. The record length of WVP observation series of each station varied between 31- and 41-years between 1962 and 2002. The monthly mean WVP observation series of each station was rearranged on seasonal basis. Sequential Mann–Kendall trend test, Sen’s slope estimator, and Spearman’s rank–order correlation tests were employed for detection of likely trends, and Kruskall–Wallis test was used to detect decadal variations in WVP series of each observation station. A possible area of representation for each meteorological station was determined by using the Thiessen polygons technique in a geographical information systems media. It was found that 15 seasonal WVP series have a positive trend covering 97% of the GAP area in the summer season; although one WVP series has a negative trend direction. However, in the spring season, 33% of the area had a positive trend, and a negative trend did not appear in any stations. WVP records in the winter season showed an increasing trend over 19% of the GAP area, whereas a decreasing trend prevailed in 9% of the area. The study results led us to conclude that the substantial increase of WVP observations in summer season could be attributed to both the shift from rain-fed agriculture to irrigated agriculture being made increasingly spacious year by year and building large water reservoirs in the GAP located in a semi-arid region. The results also indirectly suggested that the historical trends in the WVP parameters might be related to global climate change phenomenon.     

On‐line Solid Phase Extraction of Copper in Water Samples with Flow Injection Flame Atomic Absorption Spectrometry

An on‐line solid phase extraction method for the preconcentration and determination of Cu(II) by flame atomic absorption spectrometry has been described. The procedure is based on the retention of Cu(II) ions at pH 6.0 on a minicolumn packed with Amberlite XAD‐1180 resin impregnated with chrome azurol S. After preconcentration, Cu(II) ions adsorbed on the impregnated resin were eluted by 1 mol L^?1 HNO₃ solution. Several parameters, such as pH, type of eluent, flow rates of sample and eluent solutions, amount of resin were evaluated. At optimized conditions, for 3.5 min of preconcentration time, the system achieved a detection limit of 1.0 µg L^?1, and a relative standard deviation of 1.2% at 0.2 µg mL^?1 copper. An enrichment factor of 56‐fold was obtained with respect to the copper determination. The proposed method was successfully validated by the analysis of standard reference material (TMDA 54.4 lake water) and recovery studies. The method was applied to the preconcentration of Cu(II) in natural water samples.     

Structure and recent evolution of the Hazar Basin: a strike‐slip basin on the East Anatolian Fault,Eastern Turkey

The Hazar Basin is a 25 km‐long, 7 km‐wide and 216 m‐deep depression located on the central section of the East Anatolian Fault zone (eastern Turkey) and predominantly overlain by Lake Hazar. This basin has been described previously as a pull‐apart basin because of its rhombic shape and an apparent fault step‐over between the main fault traces situated at the southwestern and northeastern ends of the lake. However, detailed structural investigation beneath Lake Hazar has not been undertaken previously to verify this interpretation. Geophysical and sedimentological data from Lake Hazar were collected during field campaigns in 2006 and 2007. The analysis of this data reveals that the main strand of the East Anatolian Fault (the Master Fault) is continuous across the Hazar Basin, connecting the two segments previously assumed to be the sidewall faults of a pull‐apart structure. In the northeastern part of the lake, an asymmetrical subsiding sub‐basin, bounded by two major faults, is cross‐cut by the Master Fault, which forms a releasing bend within the lake. Comparison of the structure revealed by this study with analogue models produced for transtensional step‐overs suggests that the Hazar Basin structure represents a highly evolved pull‐apart basin, to the extent that the previous asperity has been bypassed by a linking fault. The absence of a step‐over structure at the Hazar Basin means that no significant segmentation boundary is recognised on the East Anatolian Fault between Palu and Sincik. Therefore, this fault segment is capable of causing larger earthquakes than recognised previously.