PaPRIKa: a method for estimating karst resource and source vulnerability��application to the Ouysse karst system (southwest France)

The intrinsic vulnerability mapping method, PaPRIKa, is proposed as a common basis for karst groundwater protection in France. PaPRIKa is a specialized method for studying karst aquifers, derived from updating the RISKE and EPIK methods. Both the structure and functioning of karst aquifers are considered in order to develop a resource and source-vulnerability mapping method. PaPRIKa means Protection of aquifers from the assessment of four criteria: P for protection (considering the most protective aspects among parameters related to soil cover, unsaturated zone and epikarst behavior), R for rock type, I for infiltration and Ka for karstification degree. The Ouysse karst system, located in the Causses area in southwest France, is one of the nine pilot sites where this method was tested and standardized. The specificities of the Ouysse system such as the size of the catchment area, the spatial variability of the karst network development, the thick infiltration zone and the system??s dual character (both karst and non-karst areas), have provided a valuable field of application. The vulnerability of the resource was assessed for the entire catchment area, while source-orientated cartography was attempted for the catchment areas of the three different capture works used for drinking water.     

Factors Affecting the Behaviour of Retaining Structures with Prestressed Anchorages Under 2D and 3D Conditions

Some basic factors which influence the behaviour of the anchored retaining structures are investigated and 2D analyses with three dimensional ones are compared. The parametric analysis under 2D conditions focuses on the influence of significant factors such as the normalized embedded depth of the wall, the resistance of the anchors, the free tendon length, the earth pressure coefficient at rest and the flexibility of the system, on the behaviour of the retaining structure. The analyses are performed in two groups for two representative soil types named S₁ (weathered weak rock) and S₂ (very stiff clay). Qualitative as well as quantitative conclusions are derived from the analyses concerning the influence of the above mentioned factors, mainly on the safety factor as well as on the displacements. The 3D analyses are carried out for various ratios L/H, where L is the length and H the height of the slope. Several trends are confirmed from the results concerning the influence of the above-mentioned factors. It is concluded that the triaxal conditions strongly affect the safety factor, as well as the distribution of horizontal and vertical displacements, mainly in the cases where the ratios L/H ≤ 2. Some serious deviations between 2D and 3D analyses are pointed out and the physical explanation of these differences is given for several cases.     

Palaeoenvironmental Reconstruction of a Lower Pleistocene Stratigraphic Section in Sousaki Basin,Greece, Using Fuzzy Cognitive Maps

Mathematical Geosciences - This work aims to test and introduce a newly developed methodological approach for palaeoenvironmental reconstructions using advanced intelligent controls, namely fuzzy...     

Stable elements of radioecological importance in certain echinoderm species

Echinoderms may present variations in their elementary composition according to the surrounding medium and to their food sources. The accumulation of certain trace elements by these organisms is of radioecological interest, besides the biological one. The elements cobalt, zinc, chromium, caesium, silver, tin, iron, rubidium, selenium and scandium were determined in seven echinoderm species by neutron activation analysis and γ-ray spectroscopy. In this work the calculated values of the concentration factors of the determined elements are reported and discussed from the radioecological point of view.     

Artificial neural networks as an alternative approach to groundwater numerical modelling and environmental design

Classical optimization methodologies based on mathematical theories have been developed for the solution of various constrained environmental design problems. Numerical models have been widely used to represent an environmental system accurately. The use of methodologies such as artificial neural networks (ANNs), which approximate the complicated behaviour and response of physical systems, allows the optimization of a large number of case scenarios with different set of constraints within a short period of time, whereas the corresponding simulation time using a numerical model would be prohibitive. In this paper, a combination of an ANN with a differential evolution algorithm is proposed to replace the classical finite‐element numerical model in water resources management problems. The objective of the optimization problem is to determine the optimal operational strategy for the productive pumping wells located in the northern part of Rhodes Island in Greece, to cover the water demand and maintain the water table at certain levels. The conclusions of this study show that the use of ANN as an approximation model could (a) significantly reduce the computational burden associated with the accurate simulation of complex physical systems and (b) provide solutions very close to the optimal ones for various constrained environmental design problems. Copyright © 2008 John Wiley & Sons, Ltd.     

A coupled groundwater-flow-modelling and vulnerability-mapping methodology for karstic terrain management

A coupled groundwater-flow-modelling and vulnerability-mapping methodology for the management of karst aquifers with spatial variability is developed. The methodology takes into consideration the duality of flow and recharge in karst and introduces a simple method to integrate the effect of temporal storage in the unsaturated zone. In order to investigate the applicability of the developed methodology, simulation results are validated against available field measurement data. The criteria maps from the PaPRIKa vulnerability-mapping method are used to document the groundwater flow model. The FEFLOW model is employed for the simulation of the saturated zone of Palaikastro-Chochlakies karst aquifer, in the island of Crete, Greece, for the hydrological years 2010–2012. The simulated water table reproduces typical karst characteristics, such as steep slopes and preferred drain axes, and is in good agreement with field observations. Selected calculated error indicators—Nash-Sutcliffe efficiency (NSE), root mean squared error (RMSE) and model efficiency (E′)—are within acceptable value ranges. Results indicate that different storage processes take place in different parts of the aquifer. The north-central part seems to be more sensitive to diffuse recharge, while the southern part is affected primarily by precipitation events. Sensitivity analysis is performed on the parameters of hydraulic conductivity and specific yield. The methodology is used to estimate the feasibility of artificial aquifer recharge (AAR) at the study area. Based on the developed methodology, guidelines were provided for the selection of the appropriate AAR scenario that has positive impact on the water table.