ALBERT

Notizen: The method of finite differences is applied to the computation of multi-dimensional synthetic seismograms. This paper gives a study of the mathematical and numerical formulations of the problem, the boundary conditions, the convergence conditions and how to simulate the source in both one solid or a liquid. It is shown that the numerical formulation chosen is valid both for direct and inverse problems (i.e. for modeling and migration). This formulation makes it possible to use the normal incidence reflection coefficients for P and S waves, whether they travel horizontally or vertically. The examples shown have been chosen on purpose in order to be easily interpreted. They do not give a full idea of the possibilities of the algorithm which allows to consider non-planar interfaces, except close to the vertical axis.

Notizen: Finite difference migration has been developed and popularized by J. F. Claerbout of Stanford University and is now widely used in seismic processing. For most sections finite difference migration gives results comparable to those obtained by conventional Kirchhoff migration and, where events are not dipping too much, a cleaner appearance is often apparent. However, there are two practical limitations to the method, and these occur in regions of very steep dip and where there is a large variation of the velocity in the lateral direction.It is possible to develop successively more accurate equations to deal with the steep dip problem, but above third order these schemes become prohibitively expensive to implement. The finite difference method itself introduces errors and so imposes further limitations on the angle of dip. For the effective treatment of steeply dipping beds there appears to be no method available in the time domain which does not suffer from dispersion inaccuracies. However, by developing wavenumber migration, an exact one-way wave equation can be used, and this eliminates any error except that caused by finite sampling.The other difficulty with wave migration is the correct migration in regions with lateral velocity variation. A number of approaches are possible of which three are discussed here. The first uses an exact theory, the second is based on the deviation from a depth stratified model, and the third uses a transformation to a depth co-ordinate system. All methods are discussed with their advantages and limitations. Finally, some examples are shown of wave migration applied to synthetic and real data.

Notizen: In seismic refraction surveys, in particular those using first arrival recording techniques, the hidden layer problem occurs where energy from a refractor of higher velocity arrives at the surface before energy from an overlying refractor. The maximum thickness of the hidden layer is referred to as the blind zone.Hypothetically, every recorded refractor has an associated blind zone which may or may not contain a hidden layer. For an assumed earth model of plane constant-velocity layers and stepwise increase of velocity with depth, the effect of a blind zone on an interpreted depth section may be evaluated by defining an intercept time for a blind zone of assumed or known velocity and by using standard time-term equations for layer thicknesses and depths.The treatment covers an arbitrary number of blind zones embedded within a multilayer sequence of horizontal or dipping refractors. Model calculations affirm the benefits of this approach compared with previous methods which, in general, have been restricted to the case of two horizontal layers with one intermediate blind zone.

Notizen: For a thin highly-conducting layer with given longitudinal conductance the recurrence formulae for an n-fold horizontally stratified subsoil are established for d.c. resistivity and magnetotelluric soundings. Similarly, a thin low conductivity layer with given transverse resistance is treated in the d.c. case and a non-conducting intermediate bed in magnetotellurics. Model curves for a thin high- or low-conductivity intermediate layer in the three-layer case have been carried out, which may serve as an extension of the well-known three-layer diagrams for a Schlumberger configuration. The corresponding model curves in magnetotellurics are given.By numerical comparison of these curves with real three-layer curves some diagrams have been developed to show the allowed thicknesses of the intermediate layer in the Schlumberger case and in the case of magnetotelluric sounding.

Notizen: Four radar systems at three different frequencies are described which are useful in probing into salt for finding information of interest to miners. Ranges in salt to (a) the edge of a salt dome, (b) the top of the salt dome, (c) boreholes in salt, or (d) faults or hazards ahead of mining can be determined using one or more of these radar systems. Radar wave velocities in salt are determined by radar probing through pillars of known length, and then used to determine ranges in salt to timed radar reflections. Radar probing results are shown obtained in different salt mines probing upwards and downwards. Enclosed areas in the mine are the best radar station locations to probe into salt as air reverberation of radar energy is shortened.

Notizen: A simple extension of our previous work in which digital filters were developed to transform dipole resistivity measurements over layered earth to Schlumberger ones leads us to the development of filters for transforming the latter to the former. As in the previous work we use a sampling interval of 1/6 In 10 in designing the filters that are both accurate and fast in operation.

Notizen: Seismic facies analysis makes use of different seismic parameters in order to get other than structural information. A review is given of possibilities and usefulness of seismic facies analysis in oil exploration.A seismic facies unit can be defined as a sedimentary unit which is different from adjacent units in its seismic characteristics. Parameters that should be taken into consideration in the seismic facies analysis are as follows: reflection amplitude, dominant reflection frequency, reflection polarity, interval velocity, reflection continuity, reflection configuration, abundance of reflections, geometry of seismic facies unit, and relationship with other units.Interpretation of seismic facies data may be either direct or indirect. The purpose of the direct interpretation is to find out geological causes responsible for the seismic signature of a seismic facies unit. So, the direct interpretation may be aimed at predicting lithology, fluid content, porosity, relative age, overpressured shales, type of stratification, geometry of the geological body corresponding to the seismic facies unit and its geological setting. The indirect interpretation is intended to reach some conclusions on depositional processes and environments, sediment transport direction, and some aspects of geological evolution (transgression, regression, subsidence, uplift, erosion).The results of the seismic facies analysis may be shown on seismic facies cross-sections and seismic facies maps. Depending on the available seismic data and geological conditions in the area under consideration, the seismic facies maps may be of different types such as general seismic facies maps showing distribution of different seismic facies units, sand-shale ratio maps, direction of cross-bedding and paleo-transport maps etc.Several kinds of seismic facies units and their geological interpretation are discussed as examples of seismic facies analysis.

Notizen: The reflectivity method for computing synthetic seismograms can be applied to seismic prospecting problems with special focus on coal-mining problems. The method allows the calculation of reflected waves for point-source excitation and non-vertical incidence. It automatically includes all possible conversions of wave types and all inner multiple reflections. Synthetic horizontal- and vertical-component seismogram sections are given for a simple two-seam model and for a realistic seam sequence which is represented by 48 layers; the source-receiver distances range from 100 m to 1000 m. These seismograms show prominent PS reflections already at moderate source-receiver distances. These waves complicate the vertical-component records by producing arrivals of similar strength as the PP reflections. From this it is concluded that PS reflections in strongly layered media can cause problems in routine CDP stacking. On the horizontal-component records the PS reflections are dominant. Because of the lower velocities of S waves the time resolution of PS reflections is better than that of PP reflections. This suggests that horizontal-component recording may be useful in the investigation of subsurface regions with strong velocity contrasts, even with conventional energy sources producing mainly P waves.

Notizen: Expressions for the I. P. activity coefficient for an inhomogeneous sphere with the conductivity increasing/decreasing from the core towards the periphery according to a power law have been derived.In certain geometrical situations of the electrode configurations a negative I. P. signal is obtained. The negative I. P. may be understood as due to modifications in the discharge current from the polarized medium during the discharge process.The results of the investigation may be useful for more accurate interpretation of I. P. anomalies due to isometric inhomogeneous bodies.

Notizen: Magneto-telluric experiments were performed in August 1974 in the Muhos Jotnian sedimentary formation and the Koillismaa Precambrian basement complex by the Centre de Recherches Géophysiques, Garchy, and the Department of Geophysics, University of Oulu, employing the “Résistivimètre magnéto-tellurique”, an instrument which permits apparent resistivity values to be observed at eight pre-selected frequencies between 8–1700 Hz.Preliminary soundings were made on the Muhos formation and on its surroundings, after which a magneto-telluric profile was measured involving eleven sites on a line 13 km long extending across the formation. Some further soundings were made at certain sites of known stratigraphy. The resistivity values in the sedimentary formation were found to vary between 10 ωm and 200 ωm, while those in the basement were markedly higher. This resistivity contrast suggests that the method seems to be suitable for delimiting the sedimentary formation.Soundings made on the basement at Koillismaa show apparent resistivity values in the range 1000–20000 ωm. The interpretation of these soundings was in agreement with other, independently obtained geophysical results.

Notizen: Multispectral recordings used for remote sensing are not without analogy with seismic records from CDP field set-ups. These seismic data may be regarded as “photographs’ of deep regions of the earth taken from various angles.The Karhunen-Loève (K.L.) transformation is commonly used for multispectral data processing, where it helps emphasize some features of remote sensing information. The same method may be applied to seismic data processing. Signal-to-noise ratio is improved on synthetic or field examples when K.L. transformation is applied instead of conventional CDP stacking. Residual statics seem to be diminished by a significant factor.

Notizen: A horizontally layered non-absorptive system of homogeneous layers may be specified by giving the reflection coefficients at each interface. Provided the layers have equal vertical travel time and a perfect reflector as a free surface, the reflection coefficients are generally reconstructed from the reflected pulses by way of solving simultaneous equations of the Toeplitz matrix form with the Levinson recursion method. There exists an alternative approach to solving this problem which by simple reasoning immediately turns out the (Levinson) recursion scheme. The method is based on formulas that relate to solving the forward problem. It resembles Kunetz's (1962) original inverse solution in as much as the computation of the reflection coefficients is based on the idea of separating the contribution of a primary from the sum of all multiples.

Notizen: The magneto-telluric and telluric-telluric profiling techniques are presented, and then a new method which combines these two techniques for mapping a parameter defined as the “apparent pseudo-resistivity”.The results obtained for the uranium structures in the Cluff Lake district (Saskatchewan Canada) indicate the use of these different techniques in the detection of zones of conduction for surface zones and for deeper zones, and demonstrate the advantages of these methods over the usual electrical methods in problems of structural research.

Notizen: The geological sequence rock-coal-rock represents a seismic low-velocity channel. Channel waves generated in a coal seam and their reflections from discontinuities can be used for proving the minability of the seam. To investigate the process of reflection, two-dimensional models of the sequence rock-coal-rock have been investigated by means of the ultrasonic transducer technique. Two-dimensional models have the advantage that the wave field can be observed at an arbitrarily chosen point of the model plate. Thus, by means of these models the direct and the reflected Rayleigh channel wave can be observed along their path of propagation.From the geophysical point of view the various types of discontinuities of a coal seam can be divided into two basic types: one is restricted to the seam, the other includes in addition a fractured zone in the adjoining rock.The investigation of the symmetrical Rayleigh channel wave reflected by a discontinuity yields the following results:For dip angles γ between approximately 90° and approximately 60° the reflectivity is virtually independent of the type of discontinuity. This does not hold for the limiting case of γ= 90° (vertical dip) for which the reflectivity increases with increasing influence of the fractured zone. For dip angles γ between approximately 60° and approximately 40° the reflectivity is still independent of the fractured zone but the shape of the reflected wave deteriorates with increasing influence of the fractured zone.For dip angles γ below approximately 40° the reflected wave deteriorates such that the application of the in-seam seismic reflection method will be difficult or even impossible.The conversion of the direct wave of the symmetrical fundamental mode into a reflected wave of the antisymmetrical fundamental mode has been observed.

Notizen: Analytical solutions exist for the potential of a Point Source in media with depth dependent conductivity of the form σ(z) =σ0(1 +αz)n.Of particular importance is the case of the linear gradient (n= 1). More general distributions of conductivity with depth can be approximated by equivalent sequences of homogeneous layers. Comparison between such approximations and the analytical solution for media with linear gradient of conductivity indicates that already a coarse step function yields a reasonably good approximation.

Notizen: The use of arrays to separate primary reflections from unwanted coherent seismic events is common practice in land seismic surveys. Very long source and receiver arrays have been used recently to reduce the effects of waterbottom multiples on marine seismic data.The source array consists of five uniformly spaced identical subarrays, each with five different airguns, where the distance between the subarrays may vary from 20 m56 m. The volume of each subarray is 10.3 1 (630 cu.in.) which gives a total volume of the array of 51.5 1 (3150 cu.in.) operated at a pressure of 14 MPa (2000 psi). In order to have a flexible receiver system it was decided to implement the extended receiver array in data processing by computing a weighted sum of two to five traces. The hydrophone cable consists of fifty-four channels with a group length of 50 m.Data shot with the superlong airgun array are processed by a combination of standard techniques and special procedures. In particular, the quality of the stack section is improved by using a weighted stack. The stack weights are computed by a program which takes into account the primary-to-multiple ratio.Comparisons with conventional data show significant improvements in data quality obtained by using the superlong airgun array. Examples show that the waterbottom multiples have been strongly attenuated and the deep seismic events have been enhanced.The combined array response function for dipping events is given in an appendix.

Notizen: We start from the Hankel transform of Stefanescu's integral written in the convolutionintegral form suggested by Ghosh (1971). In this way it is possible to obtain the kernel function by the linear electric filter theory. Ghosh worked out the sets of filter coefficients in frequency domain and showed the very low content of high frequencies of apparent resistivity curves.Vertical soundings in the field measure a series of apparent resistivity values at a constant increment Δx of the logarithm of electrode spacing. Without loss of information we obtain the filter coefficient series by digital convolution of the Bessel function of exponential argument with sine function of the appropriate argument. With a series of forty-one values we obtain the kernel functions from the resistivity curves to an accuracy of better than 0.5%. With the digital method it is possible to calculate easily the filter coefficients for any electrode arrangement and any cut-off frequency.

Notizen: Most of the data recorded at seismological observatories are essentially noise, not signal. One way to achieve a higher information density is to trigger the seismograph, as in strong-motion accelerographs. This approach loses the first motion—not important for earthquake-engineering studies, but very important for studies of focal mechanism. To eliminate this defect, various cumbersome techniques have been used, such as closed-loop tape-recording.Here we describe a seismograph that records only the signals and does not lose the first motion. Our procedure uses a microprocessor (MC6800) to monitor the energy level adaptively, uses a solid-state memory like a large shift-register, and has the microprocessor trigger recording from the solid-state memory onto a tape cassette whenever a signal (as defined by energy level) is recognized by the microprocessor.A field station consists of a crystal clock, seismometer, amplifier, analog-to-digital converter, Parallel Interface Adapter (PIA), MC6800 microprocessor, 8K solid-state memory, Asynchronous Communications Interface Adapter (ACIA), cassette tape-recorder, and battery. The duration of operation depends upon the frequency content of data, the sampling rate used, and the frequency of events. The design criteria used for the stations of the first field system are a 1 Hz to 10 Hz bandpass amplifier, 8-bit digitization, 5 samples per cycle of highest frequency content, and quality tape cassettes. These requirements are appropriate for exploring for magma chambers in subduction zones—the motivation for developing this system. A playback facility uses the DEC LSI-11 computer, which has an assembly language set very similar to that of the MC6800.This equipment, or a slight modification thereof, would be suitable for recording strong-motion earthquakes, for monitoring quarry blasts, or for any seismological effort in which the triggering criterion can be specified as an algorithm for programming into the microprocessor firmware. The resulting data are digital and only include significant signals, thus the data reduction facilities may properly concentrate on analysis and interpretation. Because the parameters of the system can be easily modified in firmware or software, the system is very flexible and can be considered the Universal Geophysical Recorder. An adaptation to recording transient EM phenomena is in progress. In this application, the source is controlled, but the use of the self-triggering approach eliminates the need for a radio-control system to activate the recorders, HIG Contribution no. 753.

Notizen: The problem of detecting discontinuities which interrupt coal seams is of great importance to the coal mining industry. One possible method of detecting such discontinuities is that of in-seam seismology where both source and detectors are placed under- ground on the coal face. In this paper the propagation of SH waves from a line source in the seam is investigated. There exists a particular set of waves–channel waves–, confined to the coal seam. These waves are dispersive and have an associated Airy phase whose geometrical attenuation is least. However, if absorption of energy within the coal is included then the Airy phase is the dominant wavegroup only for distances less than a certain maximum. If a detection criterion proposed by Dresen and Freystätter applies, then there is a lower limit to the frequency that should be used for exploration. This requirement may be in conflict with attenuation considerations.

Notizen: Reflections and refractions from curved interfaces were studied on two dimensional scale models. Time of arrival, amplitude and character of reflected, converted, and refracted waves were mainly used for this study. Some reflected refractions, refracted reflections and diffractions were also considered. It was possible to separate PS and SP waves and to study their amplitude and character separately. From the amplitude study of refracted arrivals it was concluded that the refracted ray path penetrates into the high velocity layer rather than propagating along the interface. Although most of the results are interesting from the theoretical point of view, a few applications to exploration problems are suggested.

Notizen: The results of specific processing of seismic sections on an actual oil field have proved that it is possible to find a link between a seismic parameter (amplitude of a reflecting horizon) and petrophysical characteristics of a reservoir whose changes modify well productivity.A good correlation appears between the values of good oil productivity and the weakness of the amplitudes of one horizon close to the oil producing layers.

Notizen: The expressions for quasi-static electromagnetic fields of a horizontal electrical dipole placed on the surface of a polarizable half-space have been derived for low and high values of induced polarization parameter and presented along with numerical results. It has been observed that the polarity of the mutual impedance function is negative for low values and positive for high values of the induced polarization parameter in the entire time domain, whereas the induced voltage function is positive for low values of induced polarization parameter and becomes negative for high values. In the case of low values of induced polarization parameter the transient electromagnetic field in the beginning increases with time, later on it starts to decay with time. The present study shows that the decay rate of electromagnetic field is highly dependent upon the induced polarization parameter. In the light of the present study the conductivity of the polarizable medium may be determined more accurately.

Notizen: Stratigraphic models are usually oversimplified by petroleum geologists, and the result is that the principles which we use for interpreting geophysical data are also over-simplified or even incorrect.Based on the marine seismic data from the Adriatic Sea, an example of prediction of a rather complex sedimentation model of detrital sediments is shown. On the basis of the stratigraphic interpretation using seismic techniques only for this some very important characteristics are discussed:— paleotopography of the valley and conditions which have given opportunity to map accurately the pre-depositional surface,— seismic signatures of the sedimentary section of the ancient valley in which we have recognized aluvial sequence and marine one.The conclusion is that there is a real opportunity for exploration of stratigraphic traps in this part of the Mediterranean Basin.

Notizen: Boreholes present a potential hazard to mining in rock salt mines. The only rock salt mine in England was almost lost when they mined into an unknown borehole open to an aquifer. Rock salt is a good transmitter of VHF radar waves, so a good method of detecting boreholes is by using radar probing. This paper investigates theoretically the detection of a borehole in advance of mining using two different radar systems, Bravo II and Charlie II. Bravo II has a peak power of 20 kW at 230 MHz and Charlie II has 3 W at 440 MHz. The borehole detectability depends critically on the radar wave attenuation in salt, which is characterized by its loss tangent, tan δ. The backscattering cross section σ of the borehole is also important. These parameters are related in the radar signal-to-noise equation which determines the signal-to-noise ratio (S/N) for a given range in salt to the borehole. Theoretically, in salt with a tan δ of 10-3, Charlie II can detect (S/N= 3 dB) a 12.7 cm borehole 225 m in advance of mining while Bravo II, using only 100 W, can detect the same borehole 680 m ahead. These values are with the antenna E field parallel to the axis of the borehole. Theory shows this antenna orientation to be optimum for maximum detection probability. For salt with a tan δ of 2 × 10-5, the smallest value measured for salt, Bravo II can detect the borehole up to 15.3 km using maximum power of 20 kW.

Notizen: The electromagnetic surface detection of underground quarries by classical methods becomes difficult when they are situated at depths greater than ten meters and when the thickness and conductivity of the superficial layers are irregular.The problem is tackled in two stages: at first using successive approximations, characteristics of the miscellaneous layers of a stratified medium are identified, and the quarries are then detected by observation of the conductivity changes of one of the lower layers. Computer interpretation, however, is necessary.The chances of detection of the quarries are considerably improved by a field localization method developed by us: computer interpretation is eliminated. The new aspect is an auxiliary transmitter which annuls the currents induced by the principal transmitter in the uppermost—generally more conductive—layers.The theoretical and experimental results show that the probability of detection of the quarries by this method are four times as high as by the classical one.

Notizen: This final part of our study of the resistivity sounding method in the presence of transitional layers deals with the direct application of the theoretical developments, previously reported, to both theoretical and field examples. The former are used to explain in more detail all steps of the direct procedure of interpreting resistivity measurements, when transitional layers with different dispositions are present in the assumed earth section. An alternate sequence of uniform and transitional layers is at first considered, then the case of a random sequence of these layers, and finally a sequence of only transitional layers. Then we give some logical considerations about the best fields of application of the new interpretation theory, with particular reference to hydrogeological, geological- structural, and mining exploration problems. Representative field examples are finally presented and discussed in detail for each of the exploration fields above listed. The comparison of the geophysical models obtained with the old interpretative scheme and the new system shows the greater resolving power of the new theory, provided that preliminary geological considerations, and where existing–borehole evidence justify the use of the new approach.

Notizen: During the last few years many airgun arrays have been designed with the objective of generating a short signature of high amplitude. For linear arrays of non-interacting airguns two rules have been derived that may help in the design or evaluation of airgun arrays. To achieve a short pressure pulse, the total available air volume has to be distributed over the individual guns in such a way that the tail of the signal, owing to the added bubble signals, becomes as flat as possible.When we think of ordering airguns according to volume, this flat signal tail can be achieved by designing the volumes such that the difference in bubble times of two adjacent guns is proportional to their volume to the power 2/3.The amplitude expected from a linear array of non-interacting airguns is limited by the physical length of the array.A graph of measured values tends to confirm this relation.No relation has been found between the total volume of an array and its amplitude.The graph also detects inefficient use of available array length of existing arrays.

Notizen: The problem of the propagation of acoustic waves in a two-dimensional layered medium can be easily solved in the frequency domain if the Dix approximation is used, i.e. when only the primary reflections are considered. The migrated data at a depth z are obtained by convolving the time section with a proper two-dimensional operator dependent on z. The same result can be obtained by multiplying their two-dimensional spectra and summing for all the values of the temporal frequency.The aspect of the operator in the time-space domain has the classic hyperbolic structure together with the prescribed temporal and spatial decay.The main advantages of the frequency domain approach consist in the noticeable computer time savings and in the better approximation. On the other hand lateral velocity variations are very difficult to be taken into account. This can be done if a space variant filter is used in the time-space domain.To reduce computer time, this filter has to be recursive; the problem has been solved by Claerbout by transforming the hyperbolic partial differential equation into a parabolic one, and using the latter to generate the recursion operator.In the presentation a method is given for the generation of recursive filters with a better phase characteristics that have a pulse response with the requested hyperbolic shape instead of the parabocli one. This allows a better migration of steeper dips.

Notizen: A spatial analysis of both continuous and discrete operators for upward continuation help us realize the problems and limitations which have been encountered before (Henderson 1960, Kontis 1971) but remained unsolved in practical application of upward continuation computation due to the finite length of data and operator in spatial domain. Various numerical examples show that an improvement of accuracy of continuation computations can be achieved through proper sampling and sufficient length of data.

Notizen: In marine gravity interpretation, the density required for the Bouguer correction is not easily measured, and, therefore, one often uses either standard values or extrapolates density from a station or a profile to an entire survey. If the real density varies, this leads to inconsistencies. In this paper a method is proposed to eliminate as much as possible the gravimetrical effects of real density variations. The principle is to apply Nettleton's method to the whole space, but also to use a continuously variable density in the Bouguer gravity computation. It is possible to avoid affecting real gravity anomalies by using stations situated on suitable area elements the optimal size of which is determined by the program. The density that is obtained is called “processing density’ because it is not a real one, but rather the resultant of the densities affect on each station. Use of the method is demonstrated on an example from the southeastern part of Bay of Biscay.

Notizen: In western Canada, the near surface weathered zone has variable velocity and is underlain by more uniform subweathering material. The uphole time is often used to compensate for the weathered zone, but there are limitations to its use.A method is proposed using the refraction delay time which is exactly proportional to the weathering correction time for several commonly assumed weathering velocity functions. The method does not require accurate determination of velocities or weathering depth nor even the depth of shot, yet is theoretically exact. A strip off time tr is used to replace the weathered zone mathematically with high velocity material where tr= zD/F, where D is the delay time and F the Blondeau factor.An algorithm using first break times is proposed that is amenable to computer use for determining D for each geophone point. F might be constant in some areas but is more likely a variable to be solved in an automatic static program. Thus, structure and residual statics can be handled at once.

Notizen: It is well known that the application of the “bright spot’ technique has been more successful in marine prospecting than in land prospecting. This is due partly to the problem of distortion of the seismic signal caused by the geophone-ground coupling, especially when carrying out high resolution, shallow seismic surveys in swampy terrain.The effect of geophone-ground coupling on the response of a single geophone to the incident compressional waves has been treated by several authors. However, they have always neglected the influence of mutual interaction between an array of geophones on the response of each geophone forming the array. We show that mutual interaction, which results from the re-radiation of the incident compressional waves by the geophones forming the array, can have considerable effect on the response of each geophone.The effect of the geophone-ground coupling on the response of a seismic channel is considered in the absence and presence of mutual interaction between a group of geophones for the case when the shear wave velocity of the soil varies by a factor of three.

Notizen: The usefulness of IP-technique for different geophysical purposes is discussed on the basis of field examples. IP and resistivity results are not always correlated, and the IP-information may be unique in prospecting for very low grade sulphide mineralizations. The IP-technique seems to be useful sometimes in prospecting for disseminated Ni-Cu- mineralizations. A massive sulphide mineralization could be localized using IP.The disturbances from different kinds of geological objects other than prospecting targets generally are smaller in IP-work than in resistivity work. It was possible to discriminate between apparent resistivity anomalies caused by shear zones and by sulphide mineralizations by means of IP-measurements. The influence of magnetite on IP- measurements is briefly discussed. The relation between ground magnetic measurements ΔZ and the IP-parameter is in many areas weak and does not seriously influence the interpretation of the IP-measurements. A high correlation between ΔZ and IP-measurements has been found on a titaniferous iron ore. This ore body gives strong IP-anomalies indicating that it is a good IP-target. Finally, the application of small moving arrays in very detailed IP-measurements is found useful for detailed mapping of a mineralized zone under a thin overburden and for determination of the dip of mineralized zones.

Notizen: It is not possible to determine accurate geological velocities from seismic velocity analysis for thin layers or complex structural features, especially under an unconformity. Instead, we can approach the problem of interval velocity with seismic amplitudes analysis and compute the reflection coefficient along the unconformity surface.An error estimation has been made on a model to test the possibility of such a method and to choose the best parameters to be used. The method has been applied on an actual case: the computed interval velocities show good correlation with the values obtained by a sonic log.

Notizen: The use of certain codes for the Vibroseis system of exploration has been investigated. The codes considered are well-known in communication theory. The effect of coding the Vibroseis input signal is the suppression of correlation noise and therefore an improvement of the signal to noise ratio.It is believed that, during the course of research, a new property of one of the codes used has been discovered.

Notizen: Gupta, V. K., and Ramani, N., 1978, A Note on Convolution and Padding for Two-Dimensional Data, Geophysical Prospecting 26, 214–217.Filtering of gridded data by means of two-dimensional generalized convolution results in a loss of data along the edges of the map. This loss can be counteracted by ‘padding’– filling the surrounding of the input map with some kind of data. Padding by algebraic extrapolation is assumed to be better than surrounding the maps with zeroes. A Føsrtran IV routine for padding by algebraic extrapolation is available from the authors.

Notizen: In a previous paper the author showed how, by computing an inverse filter in the frequency domain, an automatic compromise could be made between the conflicting requirements to spike a wavelet and to keep the attendant noise amplification within bounds. This paper extends the technique to take account of errors in the estimated shape of the wavelet defined to the deconvolution process. The drastic effects which such errors can have if they are ignored are demonstrated. A novel form of filter–called the “self-matching filter”–is defined which allows the user to limit not only the noise amplification but also the sensitivity of the filter to random uncertainties in the estimated wavelet. This is achieved by whitening the spectrum only within automatically selected pass bands whilst suppressing other noise-dominated or uncertainly defined frequency components. Conventional Wiener filtering is shown to be a special case of this more general filter, namely one in which the wavelet uncertainty is completely ignored. The type of phase spectrum which the output pulse should be designed to possess (e.g. zero phase or minimum phase) is briefly discussed.

Notizen: Hydraulic conductivity studies of a consolidated pozzolanic material indicate that heat-shrinkable tubing can be utilized to encase cylinders for use in a permeameter. The materials required for encasement of a sample include: heat-shrinkable tubing, hose clamps, polyvinyl chloride discs, glass tubing, and an electric oven. The procedure requires that the assembled PVC discs, filters, shrinkable tubing, and sample be placed on a support stand in an electric oven for three to four minutes at a temperature between 450–500° F. Upon removal from the oven, hose clamps are placed around each PVC disc. The method has several advantages. It saves time and expenses over conventional methods such as pneumatic pressurized core holders or triaxial testing units and preserves the original interstitial bore spaces of the sample.

Notizen: Sulfate sorption data determined from laboratory investigations were used to predict movement of sulfate during a field experiment of artificial ground-water recharge in a basin near Lubbock, Texas. Laboratory studies confirmed that sulfate sorption is controlled in the system by surface area, content of iron oxides and hydroxides, and pH. Predicted sulfate distribution in the unsaturated zone was made by assuming constant one-dimensional flow. Where these assumptions were met, predictions were generally good at shallow depths and for short times.At greater depths and longer times, these assumptions combined with other factors, such as changes in effective porosity, variable mineralogy, changing hydrodynamic dispersion coefficients, and variable infiltration rates contributed to the failure of the predicted values to match the observed data.It appears that sulfate distribution in the unsaturated zone during artificial recharge can be predicted by using easily derived laboratory data if the flow conditions in the field can be described adequately.

Notizen: A field instrument to determine saturated permeability is presented. It is possible to take several samples and obtain measurements quickly. The instrument, adapted for a series of measurements, permits the identification of erroneous values and allows repeated measurements. Calculating permeability values through self-made tables or nomograms make field results immediately available for the description of the cross section. Transporting the samples to the laboratory is no longer required. The instrument is sturdy, and requires little maintenance.

Notizen: Electrical power plant and solar heating systems have been proposed wherein confined ground-water aquifers are used as temporary storage reservoirs for thermal energy in the form of moderate to high temperature water (140°F-400°F; 60°C-204°C). The Water Resources Research Institute of Auburn University has performed an aquifer storage experiment involving warm water (97°F; 36°C). The objectives of the experimental program were to begin actual testing of the concept of heat storage in aquifers and to provide data for calibration of mathematical models describing the simultaneous transport of water and heat. Phase I consisted of drilling an exploratory well at the selected field site near Mobile, Alabama. Phase II involved construction of the central injection well, three observation wells, and performance of preliminary pumping tests. Phase III was devoted to construction of the remainder of the observation well field, performance of final pumping tests, and measurement of aquifer thermal properties; while Phase IV was devoted to a cycle of warm-water injection, storage, and recovery. It was concluded that heat storage aquifers must have low natural pore velocities, and care must be taken not to clog the injection well with solids or precipitated chemicals. Swelling of clays in the storage formation must be minimized, and hydraulic pressures capable of breaching the confining layers must be avoided. Mechanical and chemical clogging problems may be minimized by using formation water as influent to the heating system. For a 36-day storage of 2 million gallons, the calculated energy recovery factor of 0.69 was considered promising. Future research should be directed toward experimental studies involving larger volumes of water and high-injection temperatures. Study should be directed also to the geochemistry problem and the effect of high temperatures on the mechanical and hydraulic properties of clay confining layers.

Notizen: The distribution of nitrate, chloride and dissolved solids from ground water from the Ogallala aquifer in a 27-county area of west Texas illustrates widespread areas of poor water quality. Elements studied increased in concentration from northwest to southeast across the Southern High Plains. Northeast of a line from about Clovis, New Mexico to Lubbock, Texas, nitrate tends to be 〈45 mg/l, chloride is 〈20 mg/l, and dissolved solids are 〈400 mg/l. However, southwest of this line nitrate may exceed 60 mg/l and in some areas exceeds 170 mg/l. Chloride commonly exceeds 500 mg/l and may be 〉2000 mg/l, and dissolved solids usually exceed 1000 mg/l and may be 〉8000 mg/l. Regional distribution may be the result of long-term migration of Ogallala ground water but the present water quality and distribution, as well as time, distance, stratigraphy and permeability, suggest contamination of Ogallala ground water by vertical rather than lateral migration. Most of the high nitrate values (〉45 mg/l) occur in areas having sandy soils which have been intensively cultivated, thus leaching of nitrogen-based fertilizers is suspect. However, the high chloride and dissolved solids, which exist in essentially the same geographic area, probably represent vertical to local lateral seepage of saline water from large alkali lake basins and local vertical migration from saline Cretaceous aquifers.

Notizen: The Evangelical Lutheran Church (E.L.C.) Water Development Project, headquartered in Betul, Madhya Pradesh, India, has been involved since 1971 in developing ground-water supplies in the Satpura Hill Region of Central India. To date, over 400 wells have been drilled in crystalline rocks and more than 100 of these wells have been pump-tested to determine aquifer hydrologic characteristics.Crystalline rocks crop out in roughly 20 percent of the Satpura Hill Region and the main rock types are granite, gneiss, and schist. The crystalline-rock country is gently undulating and ground-water flow systems are of the local type being limited to small drainage basins of a few square miles in area.The controlled testing and detailed analysis of over 100 pumping tests provided an excellent opportunity to evaluate the applicability of standard analytical models for the analysis of pumping tests in crystalline-rock aquifers.Step-test data were analyzed by Rorabaugh's (1953) method and by a graphical method. The results indicate that well losses are significant in a number of wells tested and appear to be related to non-Darcian flow in the aquifer adjacent to a pumped well.Constant-rate pumping tests were used to determine aquifer transmissivity. Time-drawdown data were analyzed by the Cooper-Jacob (1946) approximation to the Theis (1935) equation and recovery data were analyzed by the residual drawdown method. Aquifer transmissivity ranged over two orders of magnitude from 102 to 104 gpd/ft (1.24 to 1.24 × 102 m2/day). Pumping-test results often enabled the prediction of aquifer conditions, such as limited aquifers, recharge and leakage boundaries, and aquifer dewatering.

Notizen: Surface-water and ground-water quality were evaluated at a site before and for four years after the area was used for entrenchment of sewage sludge. The soils in the area are sandy and are underlain by a clay barrier. Depth of the water table which in most instances is above the clay barrier is from 1.0 to 13.0 m. Water samples taken from monitoring wells, two drainage tiles located along the perimeter of the sludge trenches, a catchment pond and a nearby stream were analyzed for NO3-N, NH4-N, and CI. Increases in Cl concentrations were detected in shallow wells within the trench site perimeter 12 months after sludge entrenchment. Chloride levels peaked approximately 18 months after entrenchment and levels declined but not to background levels four years after entrenchment. Nitrate levels increased in shallow wells located within or near the trench site perimeter at 18 months after entrenchment and peaked at 30 months. Decreases in NO3-N occurred thereafter but had not reached background levels in some wells. Ammonium increases were also detected in wells recording Cl and NO3-N increases but NH4-N increases were inconsistent. Increases in Cl and NO3-N levels were recorded in wells potentially below the trench area, but these levels were less than those recorded for wells within the trench site perimeter. The data from this study indicate that contamination of ground water by leachate from sludge trenches was within the trench site perimeter with a lesser degree of contamination recorded in wells below the trench site. The drainage tiles and clay barrier may have had a significant effect on the resulting ground-water data, and caution is advised in extrapolating these results to other locations.

Notizen: Both rhodamine WT and tritium were found to be satisfactory tracers to determine the direction and velocity of flow of the secondary treated effluent from the Lake George Village Sewage Treatment Plant which is applied to natural delta sand beds by the rapid infiltration technique. The average vertical velocity in the unsaturated portion of the sand bed was approximately 0.85 m/day (2.8 ft/day). The horizontal flow in the saturated aquifer reached between 10 and 12 m/day (33–40 ft/day). The velocity appeared to decrease with distance from the sand infiltration beds, although this may have been the result of a change in direction of the major portion of the ground-water flow with the observation well not being in direct line of the direction of flow. Unfortunately, the dye could be traced only slightly less than half the distance from the sand infiltration beds to the seepage area adjacent to West Brook. Thus, a positive determination that the seepage consists primarily of sewage effluent and the ultimate time of flow to the seepage could not be determined in this study.

Notizen: The impacts of a coal-fired power plant on the ground-water system of a river floodplain wetland in central Wisconsin were quantified. The most important impacts were those related to the construction of a 200-ha cooling lake and a 28-ha ash pit.Several two-dimensional vertically-oriented steady-state models of the ground-water flow system were used to simulate ground-water flows before and after the filling of the cooling lake. The results of the simulation and supporting field evidence indicate that the creation of the cooling lake greatly altered the configuration of the flow system and increased the discharge of ground water to the wetland west of the lake by a factor of six. Moreover, ground-water temperatures have increased because of heat input from the cooling lake. Although the wetland biota are responding to the altered physical environment, the high rate of leakage from the cooling lake is not undesirable from a lake management standpoint. Seepage to the ground-water system prevents a buildup of dissolved solids which would necessitate periodic flushing of the lake and release of saline water to the Wisconsin River.Since 1975, concentrations of Ca+2 and SO4-2 have increased in ground water around the ash pit, suggesting that seepage is occurring. However, the plume of contaminated ground water is presently confined to a relatively small area around the ash pit.

Notizen: A plume of ground water enriched by liquid metal-plating effluent has formed downgradient from an industrial park in southeast Nassau County, New York. Discharges from the plant to the shallow aquifer began in the 1940's and continue to the present.Core samples of aquifer material from the plume were analyzed by oxalate extraction and dithionite-citrate-bicarbonate (DCB) extraction methods for the presence of chromium and cadmium. Results of the extraction indicate that for 1 kilogram of soil, the median concentrations of extracted chromium and cadmium in aquifer material are 7.5 and 1.1 milligrams, respectively, and the maximum concentrations are 19 and 2.3 milligrams, respectively.

Notizen: Abstract. W. Badon Ghyben and A. Herzberg are commonly credited with the first scientific description of fresh ground water floating on deeper saline water along coastal areas of the world. As C. W. Carlston has pointed out, J. DuCommun should receive the credit for the first quantitative statement of the “Ghyben-Herzberg principle,” DuCommun's work having antedated publications by both Badon Ghyben and Herzberg by more than 60 years. Moreover, two well-known scholars, Pliny the Elder and Charles Darwin also wrote on the topic long before Badon Ghyben and Herzberg.

Notizen: Flow to wells in water-table aquifers is related to anisotropy, vertical components of flow, well storage capacity, degree of well penetration, and changes in aquifer saturated thickness. The manner and extent to which these factors affect water levels may be evaluated with aquifer test data. Families of type curves describe the typical S-shaped curves of log drawdown versus log time observed around wells in water-table aquifers. Comprehensive analysis of water-table aquifer test data is possible with the array of equations derived largely in the late 195O's to 1970's. Erroneous data analysis will result unless complicating factors are fully recognized and taken into account. This paper reviews existing methods which the author accepts and recommends for ground-water investigator use.

Notizen: Many aspects of ground water involve shortest paths between two points and shortest round trips to many points. These problems are included in network theory which is not easily available to ground-water specialists. This paper introduces some of the techniques which can be solved by hand for fairly small projects. Larger networks can often be divided into districts, each of which may then be amenable to hand solution.The minimal spanning tree problem is described as background to the more useful problem of shortest path between two particular nodes. The matrix method is the simplest solution for the shortest path between all pairs of nodes and can easily be solved by hand for 30 or less nodes. This data can be used to determine which node is most centrally located and to determine a shorter round trip from one node to all others, returning to the origin. The matrix can be used for partial routes and for routing of two or more vehicles.

Notizen: This paper presents ten theses summarizing: The cyclic pattern of precipitation and runoff in the Central Valley of California and the need for cyclic storage to insure regularity and continuity in water supply; the inadequacy of surface-water storage because of evaporation losses and probable interference with ground-water recharge; the blasted hopes of Federal and State water agencies for control and management of the ground-water reservoir, because of potential conflict with private property rights; the artificial recharge by private and local enterprise; increasing emphasis in Federal and State programs upon surface reservoirs at increasing cost in money and water; the tendency of Federal policy to focus on the needs and clamors for irrigation water, with subsidies; and the availability of water from Federal projects now under construction for artificial recharge and subsurface storage, a first step to a long-range program of cyclic storage.

Notizen: Nitrogen-isotope values (δN15) of ground-water nitrate on Long Island, New York, correlate with δN15 ranges of nitrate sources which contribute to the ground-water systems. The δN15 of nitrate in water from the upper glacial aquifer, the water-table aquifer on Long Island, shows a shift from lighter values in the eastern part of the island where land is used predominantly for agriculture, to heavier values toward New York City where land is used for suburban residences with septic systems or sewers. δN15 values for inorganic fertilizer, unfertilized cultivated fields, and animal wastes show a similar shift from low to high values: −3 ‰ to +2 ‰+ 2 ‰ to + 8 ‰ and +10 ‰ to +20 ‰, respectively.Nitrogen-isotope ratios of nitrate in water from the deeper Magothy aquifer indicate a mixed source of nitrate.

Notizen: The city of San Bernardino is in a semiarid inland valley about 60 miles (100 kilometers) east of Los Angeles. The southern part of the city is traversed by the San Jacinto fault. Adjacent to the upgradient (northeast) side of the fault is a 10 square mile (26 square kilometers) area which contains a zone in the alluvial ground-water basin that formerly was under artesian pressure and consisted of swampy lands with a history of flowing wells, springs, and ground-water discharge to Warm Creek.Since about 1945, water levels have declined more than 100 feet (30 meters), and the swampy lands have dried up and are now highly urbanized. Basin replenishment by artificial recharge of imported northern California water at the base of the San Bernardino Mountains may cause ground-water levels to rise again in the area that was formerly swampy land. If this should happen, building foundations and basements could be subjected to structural damage and flooding by renewed flowing of unplugged artesian wells.The U.S. Geological Survey, in cooperation with the San Bernardino Valley Municipal Water District, is developing a two-layer digital model to aid in predicting the rate and extent of the rise in water levels. The solution to the mathematical equations used in the model was approximated numerically by the Galerkin finite-element method. The water district desires to evaluate water management alternatives, such as varying location, distribution, amounts of recharge, and pumping centers, to avoid excessive water level rises that could indicate an overfilling of the basin and could cause damage.

Notizen: A simple inexpensive device for sample collection and for monitoring of ground-water potential at many levels from a single borehole installation has been developed. The device consists of a bundle of polypropylene tubes contained inside a polyvinyl chloride (PVC) pipe that is installed in the aquifer. Each tube protrudes through the wall of the pipe at a different elevation where it serves as a point water sampler and piezometer. The tip of each tube is encased in fine-meshed stainless-steel screening. The device is best suited for use in cohesionless deposits and where the piezometric levels are close enough to ground surface to enable samples to be obtained by suction methods. It can be conveniently installed using a hollow-stem auger, driven casing or wash-boring methods. The usefulness of this multilevel sampling device has been demonstrated in detailed monitoring of a leachate plume from a sanitary landfill.

Notizen: Hydrochemical facies interpretations are useful tools for determining the flow patterns, origins, and chemical histories of ground-water masses. Factor analysis is advantageous for hydrochemical interpretations because it is independent of the number or type of variables used. Factor analysis also allows avoidance of problems of closed-number systems inherent in more traditional techniques, such as trilinear diagrams. This paper applies factor analysis to the interpretation of mixing between sulfate and bicarbonate ground-water masses. Whereas trilinear diagrams show one mixing trend (bicarbonate with sulfate waters), factor analysis allows interpretation of multiple mixing trends. These trends include the bicarbonate-sulfate trend; a sodium-, silica-, fluoride-, and temperature-mixing system that is interpreted as resulting from recharge; and a chloride-sodium system that appears to represent mixing with residual, connate water. The latter trends are identified as small-scale, chemical variations that result in dispersion of the data points about the dominant mixing trend on the trilinear diagram. Thus, factor analysis provides greater precision in identifying hydrochemical facies and interpreting their origins.

Notizen: The concepts of target size and the effective size of the detection device are basic to any search problem. The type of target in hydrogeologic studies may either be a distinct or discontinuous one or may be the optimum value in a continuum. Search patterns can be one-dimensional along a line or two-dimensional. For discontinuous targets, such as an abandoned well, some kind of grid pattern is necessary, although more effective search patterns exist if some property of the target, such as the geoelectric field, can be detected over a larger area. Search for an optimum value of a continuum, i.e. a bedrock surface, a water-table surface, etc., can be economically shortened by using adaptive search techniques. Examples of adaptive search techniques along a line are the Golden Section, Fibonacci Search, Dichotomous Search and Interval Bisection methods. The first three are based on values (depth, etc.) and the last on direction of gradient. Two-dimensional adaptive search methods include repeating lines or search using the line search methods. A completely different approach is the Sequential Simplex Search, a heuristic method which seems to be the most efficient available.

Notizen: A model system was developed for the purpose of studying the biological compatibility of aqueous industrial waste and subterranean disposal zones for injected waste. The model design incorporated devices for; anaerobic, aseptic compositing of effluent samples; collection of gases generated in the model elements; isolation of model elements against downstream contamination; and imposition of a normally-distributed waste concentration profile in the feed stream. The finished model was, with the exception of operating pressure, physically and chemically similar to an existing waste disposal aquifer, and waste degradation and population growth data obtained on the model correlated with observations of the same parameters made in the real aquifer.

Notizen: The areal distribution of 293 samples from the ground water of Merrick County, Nebraska has definite patterns of high (〉20 ppm), intermediate (10–20 ppm), and low (〈10 ppm) nitrate-nitrogen concentrations. Where contamination is present the nitrate-nitrogen concentrations are relatively homogeneous indicating large diffuse nonpoint sources. SYMAP (gray-scale mapping) indicates exceptionally good correlation between the irrigated coarse-textured soils and the higher nitrate-nitrogen levels. The obvious implication is that the nitrate-nitrogen levels are directly dependent on the leaching of nitrogenous material dispersed in or on the coarser-textured soils. The widespread use of commercial nitrogen fertilizer on irrigated corn acreages is suspected of being the major contributor of nitrate to the ground water.

Notizen: A differential equation for axisymmetric radial transient flow to a nonpenetrating well in an infinite leaky aquifer in spherical coordinate system has been formulated. A general solution for nonsteady-state flow was obtained for nonpenetrating wells in leaky artesian aquifers with a general time variable discharge function, as well as for the specific case of exponential decay discharge function. The solution is expressed in terms of standard mathematical functions.

Notizen: Drill-stem tests may be useful for such hydrogeological purposes as regional ground-water or geothermal resource studies. Water samples, hydraulic head and hydraulic conductivity may be obtained from these tests.Analysis of 41 drill-stem tests conducted for a regional ground-water study reveals that maximum pressures recorded during a test should exceed 30 percent of the full scale of the pressure gauge used in the case of bourdon-type instruments. Use of drill-stem-test data without consideration for percent deflection of the pressure recorder, even with evaluation of mechanical quality will mean that individual values of pressure head may be as much as 30 percent different from that which would be obtained in an observation well. The error is random and has a median value approximating that which would be observed in a well completed over the same interval. Use of large numbers of drill-stem tests will produce hydraulic head maps which agree with those produced by conventional observation wells.

Notizen: Seismic refraction methods can often indicate the saturated thickness of an aquifer. However, if an impermeable blind zone layer is present, it will not show up in the refraction profile. As a result, saturated thickness and transmissivity values indicated by the profile will be too high. It is thus important in many cases to look for a blind zone layer, and resistivity data combined with geological considerations are two possible ways of inferring its presence.

Notizen: Sand-box and Hele-Shaw models were used to study waste water injection into two-phase ground-water bodies. Two types of experiments were conducted: “static” experiments in which there was no movement of the fresh ground-water body with respect to the underlying salt water prior to waste injection, and “dynamic” experiments in which a fresh ground-water flow field was present prior to and during waste injection. During every experiment conducted in this study, buoyant plumes of injected effluent, which were clearly distinct from the resident aquifer liquids, formed and migrated upward into the lower portion of the fresh-water body. Three injection parameters exerted significant control on the movement of the injection plumes; the rate of effluent injection and the strength of the ambient fresh-water flow field significantly influenced both the vertical and lateral migration of the plumes, and the depth of effluent injection (with respect to the salt/ fresh-water interface) influenced the over-all shape of the plumes as well as the lateral migration of the plumes. The principal means of plume movement in these experiments appears to be by fluid displacement processes, rather than by dispersion processes.

Notizen: There is a spectrum of sea-level fluctuations that affect the water table of a small, permeable oceanic island. At the high-frequency end of the spectrum are the semi-diurnal and diurnal components of the astronomical tides. Also affecting sea-level elevation are atmospheric pressure and the temperature and salinity (hence density) of the ocean column.Changes in atmospheric pressure cause sea-level changes on the order of up to about 30 cm, by what oceanographers call the “inverted barometer effect.” As a result, pressure changes, like tides, generate waves that migrate across the water table. Amplitudes of the resultant pressure-related water-table fluctuations diminish inland. However, owing to the relatively long period of the pressure-related fluctuations, their inland attenuation is far less than that of the hydraulically analogous tides. In fact, in Bermuda for example, the pressure-related water-table fluctuations completely dominate water-table statistics that reflect day-to-day changes in elevation.Because a drop in pressure and corresponding rise in the water table accompanies passage of a storm front, which also brings a rainfall, there is commonly a coincidental, and very misleading, correlation between rainfalls and water-table rises. In island and coastal settings, non-tidal sea-level changes and their effect on the water table must be taken into account, if recharge is to be correctly evaluated from water-table data.

Notizen: Field and laboratory tests were made using suspensions of baker's yeast (Saccharomyces cerevisiae) to trace movement of microbes in artificially recharged ground water. Yeast cells penetrated more than 7 meters into a sand and gravel aquifer in less than 48 hours. It is believed that most of the cells travelled through channels formed by the solution of calcium carbonate rather than through intergranular pores. Ease and sensitivity of detection, coupled with negligible background correction, suggest that baker's yeast is an excellent choice as a tracer for this type of application.

Notizen: Abstract. Hydrogeologic and geochemical investigations have recently been made at an existing municipal supply well in the Town of Pembroke, Massachusetts, to determine the feasibility of using the Vyredox Method (Hallberg and Martinell, 1976) to remove iron and manganese from the ground water. The unique Vyredox testing procedures confirmed the existence of an active iron and manganese precipitating bacteria colony in the productive zone of the aquifer, which was causing rapid plugging of the well.

Notizen: The impact of the use of a heat pump for residential heating and cooling on ground-water temperatures was simulated by means of a mathematical model which couples the equations for ground-water flow with those for heat transport. A hypothetical case using data typical for southern Wisconsin was considered. Water was pumped from and recharged to a sandstone aquifer using a two-well system. Water was withdrawn from a deep well and injected into a shallow well during the heating cycle and during the cooling cycle the system was operated in reverse. After ten years of operation, water temperatures in the aquifer had changed less than one degree centigrade at a distance of greater than 40 meters from the wells. For the case considered, the use of heat pumps for residential heating and cooling would not adversely lower ground-water temperatures if use were restricted to sparsely populated areas. It is recommended that statutes which prohibit the injection of water directly into the subsurface be changed to allow the use of ground-water heat pumps.