Interpretation of Pumping Tests in Heterogeneous Aquifers with Constant Head Boundary

This paper investigates the impact of heterogeneity of the transmissivity field on the interpretation of steady-state pumping test data from aquifer systems delimited by constant head boundaries such as aquifers adjacent to lakes or rivers. Spatially variable transmissivity fields are randomly generated and used to simulate the drawdown due to a pumping well located at different distances from a constant head boundary. The steady-state drawdown simulated at different observation wells are then interpreted using the Hantush method (Hantush 1959). The numerical simulations show that, in contrast to the case of infinite aquifer domains, the interpreted transmissivity varies depending on well locations and the separation distance between pumping well and boundary relative to the correlation length. The ensemble-averaged estimated transmissivity varies between the geometric mean and the arithmetic mean, and can even exceed the arithmetic mean in a narrow domain adjacent to the boundary. It approaches the geometric mean of the underlying transmissivity field only if the distance between the pumping well is more than 20 times the characteristic length of the transmissivity field.     

Testing different sorting techniques in macroinvertebrate samples from running waters

With the aim of finding an efficient, standardised and practical protocol for sorting macroinvertebrate samples for water management practice, three different sorting techniques were tested: RIVPACS sorting, a modified AQEM/STAR (MAS) sorting protocol and a Live-sorting method. Based on the same AQEM/STAR sample to ensure comparable results, we compared RIVPACS and MAS sorting for 20 samples, and Live-sorting and MAS for a different set of 20 samples. Comparisons were based on both ecological and financial parameters relevant for the implementation of the EU Water Framework Directive in Germany. Parameters include recently developed multimetric assessment indices, their stream type specific core metric results, time effort and costs. While RIVPACS and MAS sorting produced similar results in terms of ecological assessment, time effort and costs, Live-sorting differed notably in all three respects. Live-sorting is the quickest and least expensive protocol, but shows higher variability than the other protocols. We discuss the differences and the level of standardisation for each of these methods.     

Norian magnetostratigraphy from the Scheiblkogel section, Austria: constraint on the origin of the Antalya Nappes, Turkey

Late Triassic magnetostratigraphic investigations in southwestern Turkey have suggested that parts of the Antalya Nappes are constituted of a melange of blocks originally deposited either in the vicinity of the northern tip of Arabia or, more surprisingly, directly north of India, in the southern hemisphere. In order to ascertain this result more clearly, we have correlated the Turkish series with Austrian sections of corresponding age from the Northern Calcareous Alps, for which the hemisphere of deposition is beyond doubt. The new magnetostratigraphic results obtained from the Scheiblkogel section (Austria) confirm the previously suggested middle to late Norian magnetic polarity sequence and support the heterogeneous character of the Antalya Nappes.     

Interannual-decadal variability of wintertime mixed layer depths in the North Pacific detected by an ensemble of ocean syntheses

Climate Dynamics - The interannual-decadal variability of the wintertime mixed layer depths (MLDs) over the North Pacific is investigated from an empirical orthogonal function (EOF) analysis of an...     

The experimental and theoretical evaluation of a twin-flap wave-energy absorbing device

A series of model experiments with a twin-flap wave-energy absorbing device is described, and the results compared with numerical predictions based on theoretical work reported by Srokosz and Evans (1979). Measurements were made of absorption efficiency, flap motion responses, and total flap forces (mooring forces), all with the supporting structure held fixed, with normal wave encounter. Both 2-D and finite-length flap experiments were conducted.Generally, fair agreement was obtained between theory and experiments with regard to efficiency vs wavenumber and applied damping coefficient was generally matched by apparent from these experiments. Maximum efficiencies approaching 100% (as predicted analytically) were confirmed by experiments. Further, the predicted behavior of curves of efficiency vs wave number and applied damping coefficient was generally matched by experimental results.Results for flap motion responses and forces showed good agreement with theory.Some basic conclusions are drawn with regard to practical design and economic considerations for a twin-flap power generating system.     

Hull component interaction and scaling for TLP hydrodynamic coefficients

The purpose of this paper is to validate a new method that can be used by offshore platform designers to estimate the added mass and hydrodynamic damping coefficients of potential Tension Leg Platform hull configurations. These coefficients are critical to the determination of the platform response particularly to high frequency motions in heave caused by sum-frequency wave forcing i.e. “springing”. Previous research has developed the means by which offshore platform designers can extrapolate anticipated full-scale hydrodynamic coefficients based on the response of individual model scale component shapes. The work presented here further evaluates the component scaling laws for a single vertical cylinder and quantifies the effects due to hydrodynamic interaction. Hydrodynamic interaction effects are established through a direct comparison between the superposition of individual hull component coefficients and those evaluated directly from complete hull configuration models. The basis of this comparison is established by the experimental evaluation of the hydrodynamic coefficients for individual hull components as well as partial and complete platform models. The results indicate that hydrodynamic interaction effects between components are small in heave, and validate component scaling and superposition as an effective means for added mass and damping coefficient estimation of prototype platforms. It is found that the dependency of damping ratio with KC for a TLP is almost identical to that of a single column, thus offering a scaling methodology for prototype damping ratio values.