Comparative study of methods for WHPA delineation

Human activities, whether agricultural, industrial, commercial, or domestic, can contribute to ground water quality deterioration. In order to protect the ground water exploited by a production well, it is essential to develop a good knowledge of the flow system and to adequately delineate the area surrounding the well within which potential contamination sources should be managed. Many methods have been developed to delineate such a wellhead protection area (WHPA). The integration of more information on the geologic and hydrogeologic characteristics of the study area increases the precision of any given WHPA delineation method. From a practical point of view, the WHPA delineation methods allowing the simplest and least expensive integration of the available information should be favored. This paper presents a comparative study in which nine different WHPA delineation methods were applied to a well and a spring in an unconfined granular aquifer and to a well in a confined highly fractured rock aquifer. These methods range from simple approaches to complex computer models. Hydrogeological mapping and numerical modeling with MODFLOW-MODPATH were used as reference methods to respectively compare the delineation of the zone of contribution and the zone of travel obtained from the various WHPA methods. Although applied to simple ground water flow systems, these methods provided a relatively wide range of results. To allow a realistic delineation of the WHPA in aquifers of variable geometry, a WHPA delineation method should ensure a water balance and include observed or calculated regional flow characteristics.     

The evolution of Petrov lake and moraine dam rupture risk (Tien-Shan,Kyrgyzstan)

An interdisciplinary study of glacier-related hazards in the Petrov lake region (Ak-Shiirak Range, the Inner Tien-Shan, Kyrgyzstan) has been undertaken to identify potential dangers to the area. A cooperative effort from experts in the fields of hydrology, glaciology, geomorphology and geophysics has been employed in this study. For the hazard assessment, evolution of the Petrov glacier and lake was reconstructed using historical reports, aerial photographs and satellite images. Geomorphological mapping and geophysical soundings was applied to the lake territory and the moraine dam. This has identified potentially hazardous areas of the dam including subsurface drainage zones and cracks that could cause a sudden extremely high discharge. In the past three decades, the Petrov lake has doubled in size, while in recent years, its area has been increasing by more than 92,000 square metres per year. Although there is no evidence for an imminent outburst, the dramatic increase in the lake’s size emphasizes the importance of this study.     

The utilization of the lunar eclipse effect for characterization of microparticles in high atmosphere

Summary The irradiation of the Moon in the shadow of the Earth during the eclipse, caused by refraction in the atmosphere, depends prevailingly on the optical properties of the middle and high atmosphere. The paper points out the feasibility of utilization of the optical thicknesses of the atmosphere measured in the Earth's shadow for the characterization of atmospheric microparticles. The results of observations of the lunar eclipse of August, 17th, 1989 are discussed in more detail, the vertical profile of particle concentration and parameter n in Junge's distribution have been determined. Based on processing this and another 25 lunar eclipses, a geographical map of the height of the upper limit of the high dust layer could finally be constructed.On leave from Astronomical Institute, Slovak Academy of Sciences     

Relation between the structure of particles of the dispersion layer and its spectral optical thickness in an optically thin environment

Summary The paper focuses on the applicability of simple optimizing methods to determining the aerosol structure based on the measured values of the spectral optical thickness of aerosol δ(λ). The necessary conditions leading to a stable solution are assessed. By applying the particle distribution function in the form of summations of modified gamma functions we obtain the simple form of δ(λ). It is not suitable for proving Gaussian functions. The application of approximate methods to determine the aerosol structure from spectral optical thickness of atmospheric aerosol is based on measurements of the direct spectral solar radiation flux density which formed a part of the radiation experiment conducted in Zingst (Germany) on the coast of the Baltic Sea in 1987. on leave from the Astronomical Institute, Slovak Academy of Sciences     

Accuracy limits of palaeomagnetic chronology

The paper deals with palaeomagnetic chronology as a statistical method. Using R. Fisher's statistics, the author derived the mean virtual pole positions, beginning with the Quaternary up to the Devonian, from data published in different countries and laboratories for the Eurasian continent up to the end of the year of 1966. From the mean pole positions the divergence of palaeomagnetic directions was computed and its value for Central Europe versus time was plotted. — Palaeomagnetic research into biostratigraphically dated rocks and mineral deposits in the Bohemian Massif has reached a stage, where it is possible to study the tectonic development of mineral deposits in relation to tectonic development of various basins, grabens and rock blocks. With respect to tectonic deformations, to the natural scattering of palaeomagnetic directions and to the accuracy in deriving the mean values of palaeomagnetic divergence, it is possible to achieve an accuracy in palaeomagnetic dating within the limits of a geological period, i.e. some tens of millions of years. Some other parameters may be used in special instances to reach a higher degree of accuracy.

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Zusammenfassung Die Arbeit behandelt die paläomagnetische Chronologie als statistische Methode im Hinblick auf die Erforschung von Lagerstätten. Mit der statistischen Methode von R. Fisher berechnet der Verfasser die mittleren Lagen der virtuellen Pole vom Quartär bis zum Devon; zur Berechnung wurden die paläomagnetischen Daten ausgenutzt, die für den eurasischen Erdteil bis 1966 veröffentlicht wurden. Von den mittleren Pollagen wurde die Divergenz der paläomagnetischen Richtungen für Mitteleuropa abgeleitet und ihr Wert wurde als Zeitfunktion graphisch dargestellt. Auf diese Weise wurde durch eine objektive Methode eine chronologische Vergleichskala ermittelt, die sich auf ein umfangreiches statistisches Material vom gesamten eurasischen Erdteil stützt. — Die paläomagnetische Erforschung der biostratigraphisch datierten Gesteine und Lagerstätten von Mineralrohstoffen auf dem Gebiet des Böhmischen Massivs ist so weit fortgeschritten, daß es möglich ist, die tektonische Entwicklung der Lagerstätten mit Bezug auf die tektonische Entwicklung verschiedener Becken, Gräben, ganzer Gesteinsblöcke usw. zu untersuchen. Mit Rücksicht auf die tektonischen Deformationen, auf den natürlichen Streubereich der paläomagnetischen Richtungen und auf den Genauigkeitsgrad der Ableitung der mittleren Werte der paläomagnetischen Divergenz besteht die Möglichkeit, bei der paläomagnetischen Datierung die Genauigkeit im Bereich von einigen zehn Millionen Jahren zu erreichen. In speziellen Fällen ist es zweckmäßig, auch andere Parameter zum Erreichen eines höheren Genauigkeitsgrades zu benützen.