ALBERT

Notes: The interpretation of Turam data is treated by means of a development of the conventional approach to this type of data. The development consists of a curve matching technique based upon a line current approximation to the true induced current pattern.The technique requires computation facilities which are readily available in modern programmable calculators.Practical examples of the use of the method illustrate that it can reveal information concerning the geometry of a conducting body which would not be gained by the conventional approach.

Notes: “Remote sensing” techniques have been used for many years as an exploration tool; broadly speaking, any method using sensors not directly connected to the earth's surface falls into this group.It is preferable, however, to use the term solely with reference to a number of new sensors which have recently become available to earth scientists for the detection of various radiations of the electromagnetic spectrum in the wave length range from 0.1 micron (UV) to some centimeters including the visible and infrared regions.Radiations artificially induced in the earth (active sensing) or spontaneous radiations (passive sensing) can be detected. Some of the bands investigated seem promising for application to geological surveys, especially using sensors on aircraft and satellites, which allow synoptic and large scale investigations.A brief account is given of the results already achieved and of future developments such as the ERTS and manned satellite (post Apollo) “earth observation” programmes.The potential role of Europe in the field is discussed.Details are given of some applications of thermal I.R. imagery to geological and vulcanological problems, with special emphasis on the research carried out in Italy.

Notes: In mathematical statistical filtering the deconvolution problem can be solved by two different methods:〈list xml:id="l1" style="custom"〉1by inverse filtering2by calculating the prediction error.Both methods are well known in the theory of Wiener filters.If, however, the generating process of the signal is known and can be described by a set of linear first order differential equations, then the Kalman filter can also be used to solve the deconvolution problem. In the case of the inverse filtering method this was shown by Bayless and Brigham (1970). But, while their method can only be used if the original signal is a colored random process, this paper shows that in the case of a white process the prediction error filtering method is a more appropriate approach. The method is extremely efficient and simple. This can be demonstrated by an example which maybe of special interest for seismic exploration.

Notes: The use of the electrical image method in calculating the potential of a source in the presence of a buried conductive sphere proves to be difficult because of the great number of terms making up the potential formula. The disadvantages contained by this method are avoided here by resorting to the theory of graphs. In view of this aim the “propagation” of the electrical images due to the sphere has been represented by an infinite graph to which an infinite matrix has been attached.Taking this as a basis several FORTRAN IV programs for the computation of resistivity pseudo-sections for various electrode configurations have been coded, and a great deal of such pseudo-sections have already been calculated with an IBM-360 computer. Using these results, recommendations regarding both the methodology of the geoelectrical prospecting of spherical shaped conductors and the most suitable way of building resistivity pseudo-sections are developed.

Notes: An account is given of the use of the square array technique in investigating the surface effects of rotational anisotropy when the axes of anisotropy are inclined to the surface. It is shown that, as with other arrays, two anisotropy parameters 〈inlineGraphic alt="inline image" href="urn:x-wiley:00168025:GPR249:GPR_249_mu1" location="equation/GPR_249_mu1.gif"/〉 and n can be derived by varying the array orientation.On the basis of these considerations, the effects of such anisotropy on the values of the mean apparent resistivity and azimuthal inhomogeneity ratio normally obtained in square array measurements is reviewed.Particular attention is paid to the variation of resistivity with orientation and it is noted that, in areas of moderate anisotropy, this variation is lower for the square than for the Schlumberger array.In addition to this advantage, the azimuthal inhomogeneity ratio obtained from square array measurements may be used to indicate the severity of anisotropy in an area and two field examples of this use are given.Where anisotropy is severe, gross variations of apparent resistivity with orientation are obtained with either square or collinear arrays. In these circumstances, the use of crossed measurements is considered and the particular stability of the crossed square array demonstrated.

Notes: Electrical resistivity sounding was attempted with success in 1960 on the surface of the Nile water in Khor Kundi El-Bahari, the starting place for the construction of the offset channel of the High Dam. The method was applied to determine the depth to the upper surface of the granite below the alluvium and Nile water. The success of the method conducted at two stations in the Khor is attributed to the favourable geological conditions of the section which consists of nearly homogeneous layers besides the good earthing conditions of electrodes dipped in water. The high resistivity contrast between water and granite facilitates interpretation of sounding curves. Factors interfering with the results of interpretation are mentioned.

Notes: This paper presents a dot chart for calculating gravity effects from two-dimensional bodies with the addition of a supplementary set of curves which can be used to determine the “end corrections” to modify the calculated effects when the length of the body is not relatively long with respect to the horizontal dimensions of the cross-section. The use of the chart is demonstrated by different examples. The results of theoretical cases amenable to mathematical treatment and computer results both compare favorably to those computed using the present chart.A fundamental incentive of constructing this chart, in a final form ready to use, is to make it available to gravity interpreters for utilization. Future effort in chart construction is thereby avoided.

Notes: By applying dynamic corrections a seismic trace recorded at a distance x from the energy source should be varied in such a way as to obtain a trace which would be recorded at zero-distance, i.e. at the source itself. Only such a zero-offset-trace contains the correct sequence of reflection coefficients (reflectivity function), whilst all other traces contain a distorted reflectivity function. In the simplest case, the reflectivity function is compressed over a shorter time whereas in more complicated cases a partial inversion of the reflectivity function results. This happens when some of the reflection hyperbolae intersect one another.The reconstruction of the true zero-offset reflectivity function by the application of dynamic corrections can only be an approximative process. In the first case mentioned we must expect a decrease in accuracy of the corrected trace in comparison with a zero-offset-trace. In the second case, where intersections of the hyperbolae occur, accurate reconstruction is clearly impossible.The problems are discussed with the help of theoretical and practical examples.

Notes: Fourier transform techniques have been used to calculate the theoretical filter (amplitude) response function of Nth order vertical derivative continuation operation. The amplitude response functions of the vertical gradient and its continuation follow from the same. These response functions are subsequently used to calculate the weighting coefficients suitable for two dimensional equispaced data. A shortening operator has been incorporated to limit the extent of the operator. For comparative study, some of the developed coefficient sets and the one presented in this paper are analysed in the frequency domain and their merits and demerits are discussed.

Notes: In this paper it is shown how one may obtain a generalized Ohm's law which relates the induced polarization electric field to the steady-state current density through the introduction of a fictitious resistivity defined as the product of the chargeability and the resistivity of a given medium.The potential generated by the induced polarization is calculated at any point in a layered earth by the same procedure as used for calculating the potential due to a point source of direct current.On the basis of the definition of the apparent chargeability ma, the expressions of ma for different stratigraphie situations are obtained, provided the IP measurements are carried out on surface with an appropriate AMNB array. These expressions may be used to plot master curves for IP vertical soundings.Finally some field experiments over sedimentary formations and the quantitative interpretation procedure are reported.

Notes: In the linear filter method of interpreting resistivity sounding data, as developed by Ghosh (1971), it appears that the filter function in the x-domain approaches an oscillating function for both large positive and large negative abscissa values. In the present note the reason for this oscillating behaviour is derived, and a possible practical application is indicated.

Notes: Amplitude spectra of input FM signals used in the vibratory source method of seismic exploration often show undesirable oscillations near the initial and terminal frequencies. These oscillations have an effect on the correlation background and distort the output signal. Considerable improvement in reducing the amplitude of these oscillations is obtained using a proper taper fuction. Attention is given to the relation between the tapering time and bandwidth of the spectrum.Analyses of the spectra of the received data from vibratory sources show considerable attenuation in comparison with the original field sweep. Since the matched filtering process will result in a series of waveforms which have the shape of the autocorrelation of the input signal, consideration is given to the autocorrelation function and its zero-lag coefficient of the FM signal in the presence of attenuation. A method has been developed which compensates for the attenuation and recovers the distortion of waveforms when the received data is correlated.The design of a waveform shaping filter for vibratory source data is given to reduce the influence of phase distortion on the received waveforms as well as to increase S/N ratio resolution. Parameters used for this filter are based on the properties of the FM signal and its autocorrelation function.Several examples from field data are presented to illustrate the methods. The results indicate that the use of the above techniques yields sections with good frequency resolution and improved S/N ratio.

Notes: The problem of a plane wave incident on a non-isotropic dipping layer lying over an isotropic conducting substratum has been studied and some numerical results are presented to show the effects of〈list xml:id="l1" style="custom"〉1) degree of anisotropy m,2) conductivity contrast between the substratum to the upper layer b,3) angle of inclination of the axis of anisotropy α,on the variation of amplitude and phase difference of the wave impedance with the normalized skin-depth (d/δ1).

Notes: Consideration of the spectral representation of gravity and magnetic fields shows the field to be the result of the convolution of factors depending on the parameters of the field. Wiener filters, calculated using model transformations, provide an optimum method for altering these factors and hence effecting field transformations.

Notes: A discussion is given of the requirements, the advantages and the methods to be considered in attempting the quantitative interpretation of gravity or magnetic fields from computed maps of the vertically derived field.The transform which is used here is the first vertical derivative (or vertical gradient) with or without downward continuation, but the computed maps are in fact obtained by a controllable Fourier method in which two kinds of operations can be simultaneously performed in complete independance: on one hand the separation of any part of the data by frequency cut-off, and on the other hand the transformation by vertical derivation or continuation of the part which is retained.Taking as raw data either actual surveys or artificially constructed maps, it is first shown how separated and transformed maps of this type can be efficiently obtained under quite flexible conditions, using a special computer program. It is further seen that for correctly controlled filterings the accuracy of the computed maps actually permits to take them as the basis for quantitative interpretation.To effect this, any one of the conventional methods which make use of equivalent model computations may in the first place be adapted to the interpretation of gradients, with the benefits, however, of an enhanced lateral separation of the anomalies and of a large attenuation of the regional effects.Particularly, the delineation of horizontal contours for even fairly complex models can often be made directly in a sufficiently safe way on the anomalies as they show on the vertical gradient maps. This greatly accelerates the process of determining equivalent model bodies.More special methods of interpretation can also be designed by taking into account first the fact that the vertical derivation of the field amounts to an operation of separation on the field's sources themselves, and in addition the availability of the frequency form of the information as a result of using a Fourier method of transform computation.Trial utilisations of various such interpretation processes of either the conventional or the less conventional type, are presented especially in connection with an interpretation study on transformed maps of parts of an offshore aeromagnetic survey (English Channel).

Notes: Generation of electrical power through the use of natural steam obtained from the Earth has the potential to be a significant source of pollution-free power. Successful future exploitation of geothermal power depends upon the development of cost-effective exploration techniques. A field experiment in the Imperial Valley of California indicates that there is a close empirical relationship between hot water deposits at depth and an anomalously high seismic background level at the surface. If this relationship proves to be a general one, it will serve as the basis of a simple and inexpensive method of geothermal exploration.

Notes: In massive rocks ground waters mainly flow in fracture zones whose permeability greatly changes depending on their filling. When studying ground-water flow in fissures, the results of observations of the electric fields of filtrational origin—which, in this case, considerably differ from those in porous media—can be used. Therefore the authors have made experiments on fissured media models. The measurements have been made in a special filtration tube with the fissured media simulated by a system of quartz glass plates. The spacings between plates were regarded as fissure widths. The observations have been made in fully open “fissures” and in those partially filled with sand or sandy-clay material.These experiments have resulted in establishing a dependence between the values of streaming potentials and pressure drops. The SP values have particularly been found to decrease with the opening of “fissures”. The most intensive electro-filtrational fields were observed at 40 per cent filling with medium grained sand. Additions of argillaceous material to the sand filler brought about sharp reductions in the intensity of electro-filtrational potentials.

Notes: During the last few years the airpulser, or air gun, has become very common as an energy source for marine seismic surveys. This paper describes the physical processes which take place during the operation of the pulser and develops theoretical results concerning the energy and frequency of the radiated signal and the amplitude decay of the secondary bubble pulses. The theory takes into account the presence of the airpulser itself which is assumed to be a rigid sphere within the bubble of released air. The theoretical results are combined and compared with measurements made of the pressure within the airpulser, the acceleration of the body of the pulser, and the amplitude and frequency of the signal radiated into the surrounding water. A formula for calculating the bubble frequency is given and a diagram made of the energy partition between mechanical losses, radiated energy, etc. Finally, a comparison is made of the energy release from the airpulser with that from TNT.

Notes: An equivalent stratum model is used to provide an explanation for the power spectrum characteristics of potential fields.The power spectrum of observed magnetic fields is found to consist of effects due to sources which can be represented by apparent monopoles and dipoles. Similarly, the power spectrum of observed gravity fields is found to consist of two groups of effects. A matched filter is proposed whereby the effects due to the two components in the potential field can be separated. As a consequence of the established theoretical expressions a scheme is suggested whereby the aliasing power of sampled data can be estimated. Also, the concepts of downward continuation, reduction to the pole, and reduction to pseudo-gravity of magnetic fields are re-examined in light of the theoretical expressions due to the equivalent stratum model.

Notes: The oscillatory character of the solution obtained by Qureshi and Mula's method for the direct determination of two-dimensional mass distributions from gravity anomalies is examined.

Notes: A number of resistivity profiles over dolerite and metadolerite dykes have been taken using Wenner and Schlumberger configurations around Dhanbad in order to find the potential of these for water accumulation. These dykes give rise to both resistivity highs and lows as compared to the background. The results are discussed in the light of known theories. Some suitable sites for water accumulation have been delineated.

Notes: Differential and difference soundings of resistivity for real, imaginary and complex values of the newly introduced parameters ν and μ are considered. The transverse and longitudinal differential soundings, known up to the present, correspond with the values ν= 1 and ν=— 1.The point of departure is the generalization of the concept of Dar Zarrouk parameters and the dimensional analogy between D.Z. resistivity and transverse and longitudinal differential resistivities. Properties of generalized D.Z. curves as well as the method of their construction are given. The examples of differential and difference curves are presented and the properties of these curves are discussed; particulary the effective spacings are determined. The problems of the realization of differential and difference soundings are considered; the bisymmetrical and asymmetrical arrays are proposed as a practical ones.

Notes: The effect of a conducting overburden on the electromagnetic response of sulphide ore-bodies has been studied with the help of quantitative electromagnetic model experiments. These experiments were conducted at a fixed, crystal controlled, frequency of 100 kHz using a number of transmitter-receiver configurations, though the results discussed here mostly pertain to a horizontal coplanar system. An analysis of the anomaly profiles—after accounting for the regional anomaly—indicates a general enhancement of the response. This is attributed (a) to the concentration of the current lines in the host-rock effected by the embedded target and (b) to the change in the phase and space orientation of the field vectors, brought about by the conducting overburden. The enhancement is most pronounced in the case of non-symmetrical bodies such as veins and ribbon-like structures represented by sheet models, but is also observed to a lesser degree for isometric structures. These results are expected to pave the way for a more accurate interpretation of the induction prospecting data.

Notes: Mit der vorliegenden Arbeit wird das Echo-Log als ein geophysikalisches Meßverfahren zur Bestimmung von Form und Volumensverteilung von Aussolungshohlräumen im Salzgebirge vorgestellt. Hierzu werden neue terminologische Begriffe wie Echo, Echostrahl, Echostrahler, Echozeit, Echogramm usw. erläutert. Weiter wird über die Meßausrüstung, Durchführung der Vermessung sowie die Ergebnisdarstellung berichtet.In einem letzten Abschnitt wird zwischen Echos, die auf einem direkten Weg von der Hohlraumfläche zurückgeworfen werden und anderen bei der Registrierung erfaßten Empfangssignalen unterschieden.In this paper the Echo-Log is presented as geophysical measuring method for determining form and volume spread of leached cavities in salt formations. Therefore, new terminological definitions like Echo, Echo Beam, Echo Transducer, Echo Time, Echogram etc. will be explained. Furthermore, also the measuring equipment, execution of a survey and the presentation of the results will be described.In the last paragraph the difference between Echo directly reflected from cavity walls and other in the cavities registered signals will be discussed.

Notes: The theory of potential field continuation is studied with a view of extending it to include continuation between non-linear surfaces. This theoretical extension is regarded as useful in reducing observed potential fields along one general surface to another general surface.It is demonstrated that the continuation operators considered in past geophysical literature are special cases of the generalized operators. In view of the tremendous growth in the art of high-speed computing it is possible to consider applications of the generalized operators. In worked examples upward continuation between a general surface and a datum is considered for the gravity field due to geometrically simple sources; this in order to test the accuracy of the digital applications. It is indicated that for observations on an undulating surface it is possible to account for considerable errors when, during interpretation, the observation locations are taken to be along a datum. For aids to profile interpretation in areas of considerable topographic relief some simple convolution operators for continuation between linear, non-parallel surfaces are proposed.

Notes: The ground follow-up of a magnetic and radiometric air survey had to cope with the usual dilemma to check a great number of anomalies within a short time. A limited aggregate of magnetic anomalies, expected to correspond to magnetite quartzites was statistically selected for ground identification by this method: the ratios length/width times amplitude were listed for all coherent contours and the calculation of the standard deviation per unit area resulted in different key-numbers for a new lithological “Salem Unit” and for the charnockitic or gneissic environment. The ground work thus directed and reduced by 85% yielded a substantial potential of iron ore. This was supported by by abundant determinations of the magnetic susceptibilities, confirming the sources of anomalies and revealing the amenabilities of iron ores for the magnetic separation process.The lines of truncation of anomalies were found to represent a system of local and regional faults and shear zones, which segregated the area into different tectonic blocks. These sutures have also provided the ways of intrusion for alkaline and basic magmae in the style of a “Rift” structure, housing several carbonatites and impregnations of metal sulphides.The airborne radiometrics obtained many uranium indications by gamma ray spectrometry. However, they led only to disseminated uranium-silicates, associated with syenites, granites and pegmatites, each emanating a characteristic photon energy spectrum. But in general the radiation of thorium prevails, marking northern Madras as a “Thorium Province”.

Notes: In the interpretation of magnetic anomalies and in paleomagnetism, the anisotropy of magnetic susceptibility is commonly neglected. Nevertheless, this property has basic significance, because, owing to susceptibility anisotropy, the directions of the vectors of induced and remanent magnetization are deflected from the direction of the Earth's magnetic field. Almost all rock types investigated possess higher or lower degree of the susceptibility anisotropy. Effusive and sedimentary rocks have the lowest degree of anisotropy. For the latter, the “masking effect” of the paramagnetic mineral components has some influence on the anisotropy degree due to the low mean susceptibility of sedimentary rocks. Metamorphic and plutonic rocks usually exhibit a considerable degree of anisotropy. The highest degree of anisotropy has been found in the rocks containing ferromagnetic minerals with mimetic fabric.The dependence of the degree of the susceptibility anisotropy on the degree of metamorphism proved to be very complicated; of the rock sequence from slates to gneisses, the transient rocks (roofing slates and mica-schist-gneisses) showed the highest degree of anisotropy. This result can be used in geology for reliable determination of these rock types.

Notes: A technique utilizing the convolution theorem is developed to obtain the time-domain electromagnetic response for a number of input pulses from the given step-function response. For illustration an idealized model of a homogeneously conducting non-permeable sphere placed in a uniform field is considered. The nature of the responses due to different types of pulses and their usefulness in estimating the constitution parameter of the sphere are discussed. To show the applicability of the suggested technique to generalized systems, calculations for a conducting permeable sphere are presented in the appendix.

Notes: De préférence, les sismographes seront disposés dans un lieu sans bruit, oú il n'y aurait pas besoin de patternes. Par contre, si les bruits sont tels qu'une patterne est nécessaire, l'objectif de la patterne est d'améliorer le rapport signal/bruit et donc de rendre le signal le plus utile possible. La patterne sera dessinée en fonction des charactéristiques du signal, des charactéristiques du bruit, et de la géologie du site.Il a été démontré que, dans le sens pratique, l'opération optimum sur les données d'une patterne est représentée par le proces “delai et somme”. L'augmentation du nombre N de senseurs sur une surface donnée diminue les espacements entre les senseurs et peut augmenter la coherence entre les bruits enrigistrés aux senseurs voisins, donnant donc moins d'amélioration au rapport signal/bruit que la √N anticipée. L'augmentation du nombre de senseurs par l'augmentation proportionnelle de la surface de la patterne peut resulter en la détérioration du signal, et peut également donner moins d'amélioration que la √N Ces deux effets, ainsi que l'élément économique, combinent à limiter le nombre de senseurs qui peuvent être employés.Bien que les données sur lesquelles l'on a basé ces conclusions soient tirées de la sismologie conventionnelle, ces principes sont également valables pour l'exploration sismique et pour d'autres mesures géophysiques qui emploient des dispositifs dans lesquelles plusieurs senseurs sont requis.

Notes: Recent improvements in instrumentation and field techniques have made time domain electromagnetic methods more acceptable. This acceptance has prompted further theoretical work for use in the interpretation of field data.The asymptotic solutions for the transient electromagnetic field components in the vicinity of a fault zone separating two media of high resistivity contrast are obtained for low frequency or late time. Excitation is by normally incident plane waves at the earth's surface. Because of the slow convergence of the asymptotic time series expansions, a numerical polygonal inversion is performed on the real part, or in-phase term, of the time-harmonic surface expressions for the electric and magnetic field components.For both impulsive and step excitation the transient electric field normal to the contact is more sensitive to changes in the structural attitude of the fault plane than the transient electric field parallel to the contact. The transient anomalous vertical magnetic field for either impulsive or step excitation appears to be most diagnostic of dip angle, although waveform shape does not seem to be significantly dependent on the slope of the fault. For dip angles greater than 90 degrees, as measured on the poorly conducting side of the contact, all field components become more insensitive as indicators of the structural attitude. The results presented here should be useful in obtaining several geologic parameters descriptive of a fault zone or lateral resistivity inhomogeneity from transient electromagnetic soundings; they should also provide an aid to differentiating with available geological information between layering effects on transient electromagnetic responses and effects largely due to lateral changes in resistivity.

Notes: Velekin and Bulgakov (1967) in an interesting model experiment while studying the transient electromagnetic response of a conductive sphere placed below a thin conductive sheet found that at the earlier stages of the transience, the composite system response corresponded to the response due to the overlying sheet alone and at the later stages, it corresponded to that of the sphere alone. To examine whether such a separation of responses due to individual components can be analytically studied and applied to other source configurations, we have analyzed an idealized model consisting of two spherical shells. We find that in corroboration with the above results, the general nature of the curve consists of two humps representing the responses dominated by the outer shell and the inner shell respectively. In addition, however, we find that the two humps gradually disappear to yield a smooth decay curve for increasing values of the ratio σd1b/σ2d2a (where σ1, σ2 are the conductivities, d1, d2 are the thicknesses of the outer and inner shells respectively, and b and a are their respective distances from the centre) and the effect of inner shell on the composite system response is considerably reduced.

Notes: It has been necessary to resort to the use of “long-line” refraction marine operations in certain areas where it proved impossible to eliminate singing from reflection records despite the number and variety of programs at our disposal for this purpose.Experience has shown that manual processing of offshore refraction records takes a disproportionate length of time in comparison with the surveys themselves, and this is incompatible with the requirements for choosing the site of an exploration well. It thus became necessary to find an “industrial approach” to the solution of this processing problem.It was apparent that automatic picking could also facilitate the interpretation of land refraction data, and that in the case of both marine and land work the interpretations would be more accurate when factors were taken into account which could not be considered when working without the aid of a digital computer.For these reasons a set of programs was developed for automatic picking and interpretation of refracted arrivals.The picking itself consists in searching for the maximum values of the normalized cross-correlation functions of the traces with a “model” trace. The first results thus supplied are: “picked” times, intercept times, maximum values of the correlations, and the values of the tie constants between overlapping spreads.Next, the construction of the relative intercept time curves is performed; a statistical analysis of these curves then allows the determination of the offset distance.From these elements,⊙ either the delay time curve is produced, after ensuring correct reciprocal times by means of additional minor corrections.Such work is carried out in order to enable the geophysicist to gain a sound idea of the quality of the interpretation. To assist in this aim, part of the trace on both sides of the pick is plotted on the final documents. Valid groupings of several traces involving the same amount of refraction data are thus possible.⊙ or the refractor depth is constructed with the wavefront method, making use of the relative intercept times.Such a procedure, which is normally applied to first breaks, can also be used for later arrivals exhibiting slight interference and should represent an important step towards processing secondary arrivals with high interference.The development of this package, in response to a need which is shared by both SNPA and CGG, is the result of the joint efforts of the Geophysical Group of SNPA's Pau Research Center and CGG's Technical and Scientific Departments.

Notes: This paper is concerned with an application of the Kalman filter to integrated navigation systems. It is shown that this filter is well adapted to resetting the dead-reckoning position by means of a radio-hyperbolic system or of a Doppler sonar. The algorithm can also be used for resetting the dead-reckoning position by means of a satellite navigation system.The first part is briefly concerned with stochastic processes and system theory. The canonical equations for navigation problems are written. The second part is devoted to the Kalman filter. The third part discusses the application of the algorithm to navigation problems and presents some simulation results.

Notes: The expression for the potential due to a point source of current, placed on the surface of a horizontal three-layer earth, has been derived when conductivity in the second layer varies linearly with depth and changes abruptly at the boundaries. Master curves for Wenner and Schlumberger configurations have been presented for an insulating basement and for one value of conductivity gradient in the second layer.

Notes: Using a method and definition given earlier (Roy and Apparao, 1971), this paper computes the depths of investigation in homogeneous ground for (a) the Wenner α, β and γ configurations, (b) the three electrode system and (c) the dipole-dipole arrangements when the dipole lengths are not infinitesimally small. The results for (a) and (b) have been summarised in a table, while those for (c) are shown as contour diagrams. In all the dipolar arrangements examined in this paper, except the equatorial, the depth of investigation decreases (and the vertical resolution increases) with increase in any or both of the dipole lengths. For the equatorial set up, this decrease (or increase) is very small.

Notes: The unsuitability of a particular method of computation of second derivative to varying types of field problems evinces the need of a method by which it may be possible to obtain a wide range of filters. This requirement is achieved by incorporating a mathematical smoothing operator, e-λρ2, λ and ρ being the smoothing parameter and radial frequency respectively, in the theoretical frequency response of second derivative operation. A few sets of weights for various smoothing parameters, are presented. The analysis of Bouguer gravity anomaly map of Los Angeles Basin, California, U.S.A., is carried out by Elkins's (1951) and Rosenbach's (1953) methods and the sets of weights given in this paper which clearly establishes their filtering equivalence.

Notes: The computation method described in this paper is based on the existence of a linear relationship between the mutual coupling ratio and the kernel function in the integral expression for it. Accordingly, the mutual coupling ratio can be determined by first computing sample values of the kernel function and then subjecting these to a digital linear filter. In the present paper the appropriate sampling distance is determined and the values of the digital filter coefficients are computed, both for electromagnetic sounding with horizontal coils and for electromagnetic sounding with perpendicular coils.

Notes: Design procedures and characteristics of three stacking filters are discussed which may find application in various three-dimensional velocity filtering problems. These filters are derived in the time-domain as optimum multichannel Wiener filters. Random stationary functions are assumed as stochastic models for the seismic traces. All power and crosspower spectra which are the basic elements of the multichannel normal equations are statistically averaged according to specific three-dimensional considerations. Various properties of the input traces may be incorporated in the design of the optimum filters. With fairly general assumptions about the input these filters are deterministic in the sense that they are applicable to a broad class of input traces with similar statistics in amplitudes and arrival times of signals.

Notes: An airborne magnetic survey of an area of 580 km2 centred on Gosses Bluff was flown in 1968. This survey formed part of a joint project by the Australian Bureau of Mineral Resources and the United States Geological Survey to evaluate the hypothesis that Gosses Bluff is of impact origin.Analyses of the magnetic data show that shallow sources of magnetic disturbance flank the Bluff on its southern side. Interpretation of the magnetic anomalies indicates their source to be shock-melted breccias of possible Jurassic age.

Notes: The interpretation of the gravity anomaly on a horizontal plane over a causative body having circular symmetry about a vertical axis is considered from a rather unconventional approach. As the analytical expression for the gravity effect of a circular body assumes a closed form only on the axis of symmetry, the interpretation in this approach is carried out with the anomaly profile along the axis—which leads to simpler and faster computation.A numerical method is developed for computation of the anomaly profile along the vertical axis from the horizontal radial profile of the symmetric anomaly by upward continuation. Provision is also made for an end correction when the radial profile has only a limited extension.Some simple geometrical shapes are assumed for the causative body. Its parameters are then determined from least squares fitting of its gravity effects to the observed (upward continued) vertical profile (i) by the steepest descent method and (ii) by the Newton-Raphson method.Some applications of these methods are demonstrated.

Notes: In comparing the similarity between time, frequency, and phase measurements as used in the induced polarization method of geophysical prospecting, parameters must first be defined and the basis for comparison established. The conditions for mathematical equivalence then follow in a natural sequence. Laboratory measurements are made on a variety of rock samples to indicate the type of comparison and correlation expected from field measurements.Results indicate that frequency domain and phase measurements are equivalent, but two frequency domain measurements are needed to produce the same amount of polarization information as a single phase measurement. Frequency and time domain measurements will be similar but never equivalent due to the basic differences in their respective parameter definitions.

Notes: From seismic surveys zero offset reflection times and root-mean-square velocities are obtained. By use of Dix-Krey's formula, the interval velocities can be calculated.If no well velocity survey exists, the interval velocities and T(o) times are the only available information. The suggested way to get a regionally valid velocity distribution is to select N“leading horizons”, where a major change in the velocity parameters occurs and to compute the parameters of the selected velocity depth function (in most cases linear increase with depth) by a special approximation for the interval between two adjacent “leading horizons”.Herewith all reflection horizons within the interval are taken into account.

Notes: A frequency-domain analysis is outlined for a conducting sphere in a uniform Input field: inequispaced alternating half-sine wave pulses. The Barringer Input air-borne electromagnetic exploration system uses such source fields. Theoretical profiles of Hρ(t), the horizontal magnetic component over the sphere from different elevations and for various conductivity and geometrical factors are presented. Based on these results some useful features such as penetration and detectibility are discussed.

Notes: In this paper an idealized valley of a semi-elliptic cross-section is considered. For a Schlumberger configuration on the axis, sets of master curves are calculated for the ratio of semi-axis a/b= 1, 2, 3, 4, 5 in corresponding to various resistivity ratios of surrounding rocks and valley sediments. For small resistivity ratios, these model curves have the shape of three-layer curves for horizontal bedding and are often equivalent to them within the accuracy of measurements. The axial ratio a/b considerably affects the depth determination of valley sediments. In the special case of a circular cross-section (a/b= 1) the influence of the position of the electrodes on the sounding curve is studied in more detail.The application of the master curves in practice shows that the influence of the specific shape of the valley on soundings should not be neglected. In general, the valleys have a greater “true” depth than can be seen from the interpretation of a sounding by master curves corresponding to the horizontal bedding.

Notes: Ground-water irrigation has developed rapidly in the High Plains region of the United States, especially in Texas since the 1930's and more recently in western Kansas. Although most land sales transactions do not show the water value separate from the dry land value, the availability of ground water has greatly affected land values. This study measures this effect by two methods for an area of southwestern Kansas where ground-water irrigation has become important.The purchasers of all farm land sold in the selected area between 1962-67 were surveyed to obtain information on sale price and numerous factors which it was thought might have a bearing on the land value. One method of measuring the effect of ground water on land value involved matching a number of tracts not known to have available ground water for irrigation with an equal number having ground water. Since other factors were matched as closely as possible, the differences in land value were attributed to water. The second method was multiple regression in which total tract land value and land value per acre for some 160 tracts were related to several factors–soil and topographic conditions, tract size, availability of ground water for irrigation, nearness to elevator, mineral rights, and wheat allotment. Both methods produced approximately the same results–for the period studied the availability of ground water for irrigation contributed $95 to $100 per acre to the value of the land.

Notes: In the Rothschild area, Wisconsin, most water wells are completed in glacial deposits. When glacial deposits are unsaturated or thin, wells are completed in fractured crystalline rocks of Pre-Cambrian age. Specific capacity data from 56 wells tapping these fractured rocks reveal:〈list xml:id="l1" style="custom"〉1Yields and specific capacity are generally small, with a median specific capacity of log 0.17 gpm/ft and a mean value of log 0.10 gpm/ft.2Wells which are close together may have substantially different specific capacities.3The occurrence of saturated sand and gravel above the crystalline rocks has no obvious influence on yield or specific capacity.4Specific capacities of wells seem to be inversely proportional to (a) thickness of rocks penetrated below the water table, (b) depth of the wells below the water table, and (c) depth of the wells below the land surface.Assuming that specific capacities of wells are related to the number of contributing fractures penetrated and that the number of fractures diminishes linearly with depth, the following relation is derived: 〈displayedItem type="mathematics" xml:id="mu1" numbered="no"〉〈mediaResource alt="image" href="urn:x-wiley:0017467X:GWAT37:GWAT_37_mu1"/〉 where Sc= specific capacity, Q = discharge, s = drawdown, B = a constant, b = fracture frequency at the land surface, z = depth, and E = maximum depth of fracturing. In the Rothschild area, E = 100 feet.In exploring for ground water in a fractured rock, the problem is to find the area of maximum b. If sound scientific methods are not available, then exploration will consist of drilling wells at random until a satisfactory well is completed. However, because wells achieve 60 to 80 percent of their yield in the first 20 feet below the water table, test wells should be pump tested when they have reached a depth of about 20 feet below the water table. Unsuccessful wells need not be drilled to completion.

Notes: Despite rainfalls which commonly exceed 200 inches per year in the mountainous portions of many of the islands in the Hawaiian chain, most streams in the islands are very flashy, and only a few carry water throughout the year. This is owing to the extremely permeable nature of the volcanic rocks and soils which make up the Hawaiian islands, and, in fact, the permeability of some of the younger volcanic rocks is so great that virtually no runoff occurs. As a result, development of reliable year-round sources of surface water is difficult especially on the leeward portions of the islands. Furthermore, surface storage is difficult because of the high infiltration capacities of the rock and soil cover. Consequently, development of ground water provides the most abundant and the most reliable source of water supply for these islands. Three modes of fresh ground-water occurrence may be distinguished: perched, dike-confined, and basal. Although perched and dike-confined ground water are of considerable local importance, the basal ground-water body is by far the most widely developed and most important source of fresh ground water for these islands.

Notes: This is the second part of a two-part series (Kent and Sendlein, 1972) in which an approximation of the quantity of bedrock recharge is made. Procedures used for the definition of the ground-water system were described in Part I. In Part II, a subsurface ground-water budget equates subsurface recharge from the bedrock aquifer to discharge through sand and gravel and to discharge by pumping. The Darcy equation is used to compute recharge and discharge volume flow rates. Estimates of permeability were obtained from existing pump-test data and the hydraulic gradients were determined from the piezometric map. Two conceptual models are proposed to account for the maximum and minimum cross sectional areas of the bedrock aquifer through which ground water could flow into the sands and gravel and thus are used to represent the maximum and minimum limits of recharge. Upper, lower and average values of bedrock recharge are determined for each model and compared with the average natural discharge for the entire ground-water basin (“total basin” approach). Comparisons are also made for portions of the basin (“partial basin” approach). Upper and lower limits of recharge are chosen from recharge values which are nearest to the average discharge estimate. This determination is based on the assumption that recharge is equal to discharge. Results of this study indicate a quantity of bedrock recharge between a lower limit of 0.23 mgpd and an upper limit of 2.5 mgpd is possible for an 800-square mile basin.The purpose of this approach is to provide an approximation of ground-water recharge from bedrock into an unconfined unconsolidated ground-water basin, and to provide an estimate of its importance to urban ground-water use.

Notes: Book Reviewed in this article:WATER PUBLICATIONS OF STATE AGENCIES complied by Gerald J. Giefer.

Notes: The disposal of all types of liquid and solid wastes threatens the health and well-being of mankind. In recent years the constraints on the disposal of industrial and municipal wastes into rivers and the seas have prompted the disposal through wells into the subsurface. Limestone terrane is particularly amenable to the acceptance of all types of wastes in the cavernous subsurface, and has resulted in widespread contamination of shallow ground-water resources. Highway salting has caused the contamination of thousands of household wells, causing large-scale replacement drilling programs in some northern States. A semantics problem also has arisen, because liquid wastes injected into the subsurface have not been disposed of, but rather have been placed in a new environment. They may be in storage, they may be attenuating, or they may be changing character by reaction with the rock mass or formation fluids.The U. S. Geological Survey has been concerned with the study of ground-water resources for more than 80 years, and with the problems of radioactive waste contamination since World War II. A newly identified program of investigations of waste emplacement into the subsurface was begun two years ago. The purpose of the program is to develop the ability to predict the fate of any wastes deliberately or accidentally emplaced in the subsurface. The program includes research contracts and grants with universities and governmental organizations as well as in-house research.

Notes: In the formerly glaciated Midwest, bedrock formations commonly are denser than overlying glacial sediments. Thus, gravity anomalies have a direct relationship to bedrock topography. Where the density contrast between the glacial sediments and the bedrock is known, the anomalies can be used to map the bedrock configuration if they can be isolated from gravity anomalies originating elsewhere in the geologic section. A method of isolating bedrock topography gravity anomalies is suggested based upon known bedrock elevations obtained from drillhole data. A regional gravity anomaly map is prepared by subtracting the excess gravitational effect of the known bedrock relief above a datum from the observed gravity anomalies at all drillhole sites. The regional gravity anomaly map is subtracted from the observed anomaly map to obtain a residual anomaly map reflecting the bedrock topography. The bedrock configuration can be calculated directly from this map. This method of isolating bedrock topography anomalies was found to be superior to the use of cross-profiling and least-squares polynomial approximation procedures in a study of Kalamazoo County, Michigan. The bedrock topography map of this County determined by the gravity-geologic method shows a complex bedrock topography and drainage system.

Notes: If there are gravity data and some geological information available from the region of an intermontane basin, then the volume of saturated sediments, volume of ground water available from storage, and the total volume of ground water can be determined from the gravitationally determined anomalous mass. The anomalous mass occurs because of a density contrast which exists between low density alluvium and high density bedrock which define the surface and subsurface boundaries of the basin. The gravity effect of the anomalous mass can be detected by a gravity survey of the basin after which it can be separated from other gravity effects by a regional-residual separation. The anomalous mass is uniquely determined by applying Gauss's theorem to the residual gravity map.A model of an intermontane basin is developed which relates the anomalous mass to the total volume of saturated sediments. The total volume of saturated sediments is determined from the anomalous mass, the density contrasts between unsaturated and saturated alluvium and bedrock, the area of the basin, and the water table depth.The volume of water available from storage and the total volume of water in the basin are determined from the volume of saturated sediments and the storage coefficient and porosity of the sediments.The method is illustrated by a case history from Avra Valley, Arizona. It is concluded that the major advantage of this method occurs when well data are not available, because it eliminates the need for arbitrary assumptions about subsurface basin geometry to determine the volume of saturated sediments.

Notes: This paper presents some of the preliminary results of a theoretical analysis of the ground-water infill rate of a rubble chimney produced by an underground nuclear explosion. The study was conducted to evaluate effects that various features of the hydrogeology regime have on rate of infill. This model for infill is based on the analogy of a rubble chimney to a small diameter gravity well. The infill history is approximated by integrating production from a series of steady state infill rates based on Dupuit-Forchheimer assumptions. The model has been used for parameter sensitivity analysis. Of the aquifer characteristics, changes of the hydraulic conductivity have the greatest effect on infill; the radius of influence is most sensitive to changes in the specific yield. The effect of infill rate of using a rubble porosity that decreases with depth is small, although initial infill is more rapid. The hydrogeology data from two events where infill data are available have been used with this model for verification. For both BILBY and GREELEY events, agreement between measured and calculated infill data are good. BILBY data suggest that substantial dewatering of the rubble in the chimney occurred before much ground water entered the chimney. Comparison of the GREELEY data indicates that dewatering of the rubble is minimal but that porosity of the rubble near the surface was higher than originally anticipated.

Notes: Leaching of heavy metals by ground water passing through mine tailings is caused by the oxidation of sulfides through the action of microorganisms. The pH of the ground water entering the tailings system is reduced by mechanisms within the tailings system itself. Action of sulfide-oxidizing and sulfur-oxidizing bacteria causes the formation of sulfuric acid, thereby increasing the H+ and SO42− concentration within the system. Metal ions go into solution as metal sulfates, and the concentration of H2S increases by the interaction of H+ and S2− Increase in H2S creates an environment suitable for the growth of sulfate-reducing bacteria which converts SO42− to S2− and simultaneously precipitates metal sulfides at a pH near 6.6. Decrease in pH with depth destroys sulfate-reducing bacteria, and dissolution and leaching of the tailings increase.Four lines of evidence demonstrate the presence of microorganisms in the tailings system: (1) Fe-Mn concretions below the water table at Cataldo Mission Flats, (2) fixation of Na and K below the water table, (3) precipitation of sulfate salts on the surface of Cataldo Mission Flats, and (4) experiments on two sets of tailings samples, one from the surface which showed predominant aerobic activity and one from below the water table which showed predominant anaerobic activity. Where oxygen is sufficient, iron oxidizing bacteria oxidize Fe2+ to Fe3+ which forms an insoluble hydroxide. Consequently, very little iron is found in the ground water coming from the system. The combination of these mechanisms produces poor-quality ground water with respect to metals.

Notes: Chemical analyses of natural water may be inadequate because of inadvertent human errors and sample aging. Characteristic deficiencies can be demonstrated by multiple chemical analyses of the same sample by different laboratories, multiple analyses of the same sample by one laboratory, repeated analyses of one sample as a function of time, and a simple laboratory experiment in rock-water chemistry. Whenever possible, complete chemical analyses should be made. The most reliable analyses are those in which combining weights of the cation equal the combining weight of the anion and in which the sum of the individually measured constituents equals the observed residue on evaporation at 180°C (total dissolved solids).

Notes: Corrosion and incrustation of water wells is defined and classified into groups which fit most field problems. Case histories with concomitant water analyses are described. A readily determined index for the magnitude of corrosion is presented along with recommended materials to correspond with the indices. The theory for the most common well incrustants is presented. Recommendations are made for minimizing the rate of incrustation in wells supplying water known to be incrusting and thus eventually clogging well screens. Treatments for incrusted wells are described including iron bacteria. A ten-year case history of iron bacteria fouling is presented. Nonmetallics are discussed.Descriptors: Well failures, corrosion of well components, incrustation of screens, water analyses, index, guide lines, nonmetallics, iron bacteria.Identifiers: Corrosion and incrustation problems in wells.

Notes: Standard resistivity configurations lose resolution in regions where multiple geologic layering of high conductivity contrast occurs. To partially circumvent this problem an electrode configuration was used, which includes a current electrode at depth down a drill hole in a water field, to examine the possibility of delineating ground-water flow channels. Results show the value of this technique in enhancing the electrical anomaly and hence determining structure. It was found that the ground water in this area flows primarily in fracture traces in the dolomite. Moreover, it was determined from well log synthesis that these fracture traces increase the effective porosity in the flow region by approximately ten percent.

Notes: Quality of water is determined by chemical analyses, the data from which are used for various purposes, such as classification, analysis, correlation, etc. For these purposes, the data need to be compiled and statistically evaluated. Graphical and numerical interpretation, a basic tool in hydrochemical studies, is one of the means used for summarizing and presenting water-quality data. There exist a considerable number of methods and procedures which can be applied. They are relatively simple and can be used without extensive knowledge of chemistry. Main techniques and methods are grouped, for the purpose of discussion, into four categories as to their possible use: classification methods, correlation methods, analytic methods, and synthetic and illustrative methods. The basic graphs and diagrams in each category are accompanied by examples.

Notes: A survey of State water agency and university personnel was conducted to identify and classify interstate and international aquifer problems in the conterminous United States. Questionnaires returned identified nearly 200 of such situations. Of these, 30 situations were classified as being a major problem at the present time. An additional 73 situations were classified as minor at the present time. For those problems that were indicated as being expected to develop within the next five years, 9 were classified as major and 25 as minor. For those problems that were indicated as being expected to develop after five or more years, 19 were classified as major and 42 as minor.

Notes: Appropriate nonparametric or distribution free statistical techniques are useful tools when data do not satisfy the conditions required by parametric statistical tests, and may be applied to a variety of hydrogeological problems. Two nonparametric tests, Krusk-Wallis One-Way Analysis of Variance and Mann-Whitney U Test, were used to test the significance of observed differences in well yields with respect to variation in controlling hydrogeologic factors. This paper presents the steps involved in performing these two tests with one example for each and suggests other applications to water-related problems. To avoid computational errors and save time, a computer program was written for calculating the statistics used in these tests.

Notes: Salty ground water is commonly encountered at relatively shallow depths of 100 to 300 feet beneath the major stream channels in the western half of West Virginia. Because of the wide distribution of salty ground water and connate brine at various depths, it is difficult to distinguish natural contamination from that caused by subsurface industrial activities. Natural changes in quality apparently are minor. The available historical data indicate no large-scale natural variations in salt content during the period of record. Histories of some water well developments show unnatural large-scale increases in salt content from various industrial activities that affect the fresh water zones. Some records also reveal decreases in salt content after the source of the salt was eliminated or after the subsurface activity responsible for artificial migration of the salt water was stopped.Artesian brine contaminated a fresh water aquifer in Fayette County. Chloride content changed from 53 mg/l to more than 1,900 mg/l in a period of 5½ years. When pumping was stopped, chloride content decreased to 55 mg/l in 10 years.Heavy pumping of well fields in Charleston during 1930 to 1956 accelerated migration upward of salt water. Chloride content increased from less than 100 mg/l to more than 300 mg/l in some wells and to more than 1,000 mg/l at individual wells. Pumpage has declined greatly since 1956 and chloride content has decreased below 200 mg/l at some of the contaminated wells.In an oil field of Kanawha County, a water well was contaminated by salt water accelerated by subsurface activities. Chloride content increased from less than 100 mg/l to more than 2,900 mg/l within 2 months. After the oil-field activity was curtailed, chloride content decreased to 190 mg/l in about 2½ years. Road salt piles contaminated a carbonate aquifer in Monroe County. Chloride concentrations in wells located 1,500 feet from the piles increased from 185 mg/l to 1,000 mg/l in 5 years. The greatest change was 1,000 mg/l in 1969 to 7,200 mg/l in 1970 when the salt storage area was enlarged. All salt piles were removed in late 1970 and within 2 months chloride content decreased to 188 mg/l.

Notes: Development of mountain homesites is accelerating in the Rocky Mountains of central Colorado. These homesites often require individual water wells and sewage disposal systems. Unfortunately, the widely used septic tankleach field system generally is not suited for use in the mountainous terrain where soils are thin or missing. Although current federal regulations call for six feet or more of soil at the leach field site, many of the individual sewage disposal systems now in operation in the Rocky Mountain Region of Colorado fail to meet this requirement. Sewage effluent at these sites may directly enter bedrock fractures and travel large distances without being purified. As a consequence, contamination of streams, lakes, and ground water from these malfunctioning leach fields has become a problem of increasing magnitude.Investigations of geologic, topographic, and hydrologic conditions at over 100 homesites in the Rocky Mountains of north-central Colorado have resulted in the development of objective criteria for evaluating pollution potential at mountain homesites. In addition, the results of these investigations indicate that contamination of water wells may be decreased significantly where geologic conditions are considered in the selection of sites for leach fields and wells. Although the results of these studies should be considered preliminary, they do tend to confirm that the orientation of jointing surfaces in the bedrock significantly affects the travel path of contaminants.

Notes: The inter-relationships between an industrial plant and a shallow sand aquifer of glacial origin are described. These relationships include industrial and potable water supplies, industrial and human waste water disposal systems, the hydraulics of the pollution of the ground-water aquifer and the types of corrective actions taken to re-establish the wise use of the ground-water resource. Also reviewed are the ground-water movement-quality relationship, well designs, method of drilling, well redevelopment and ground-water recharge.

Notes: Mining operations within the Coeur d'Alene District of northern Idaho have been continuous for over 85 years. Data presented herein demonstrate that early day mining and milling wastes are now affecting the ground-water quality in several locations. One of the affected areas is the lower Canyon Creek Basin located in the Coeur d'Alene District near Wallace, Idaho.Ground-water pollution of the Canyon Creek Basin results from leaching of old mine tailings that are intermixed with the upper part of the sand and gravel aquifer. High zinc, lead and cadmium concentrations occur in ground water and soil samples taken from the portion of the sand and gravel aquifer containing old mine tailings.Analysis of water samples from a settling pond located in the upper portion of the study area indicates that the pond water is not the source of the heavy metal concentrations found in the ground water. However, the water from the pond's decanting system provides recharge to ground water and compounds the problem.

Notes: Natural concentrations of nitrate are quite low in most ground waters in the eastern part of the San Joaquin Valley. High nitrate contents are related to sewage effluent percolation ponds, septic tank disposal systems, industrial waste-waters, and agricultural fertilizers. Hydrologic factors are closely related to the occurrence of nitrate. Transmissibility of the aquifer, hardpan development in the soil, canal recharge, and cobble zones in the subsurface are the primary factors of importance. Nitrate is stratified in the aquifer beneath unsewered metropolitan areas and highest contents occur in the upper 50 or 60 feet. Water quality hydrographs were used to show long- and short-term trends in nitrate. Chloride and nitrate hydrographs, trilinear diagrams, the distribution of other constituents, and hydrologic data were used to effectively delineate sources of nitrate in areas where numerous potential sources were present. Conclusions from ground-water data agree well with previous studies in other areas beneath unsewered tracts and near sewage treatment plants in which attention was focused primarily on the soil or the unsaturated zone.

Notes: Vertical shafts are roughly cylindrical voids in carbonate rocks. They range in diameter from inches to tens of feet and in height from inches to hundreds of feet. They are produced by vertically descending ground water from perched ground-water reservoirs or surface water. These features are common throughout the Interior Lowlands and Appalachian Plateaus Provinces. Vertical shafts form the headwater termini of complex drainage networks that aggregate the waters into master drains which carry the water to big springs. The drains evolve through time as base level is lowered but retain a dendritic pattern. Shafts are very short lived and occur only near the edge of the clastic caprock in the study area in south central Kentucky. Shafts are formed by free flowing sheets or films of vadose water streaming down the walls in supercritical flow. These waters are undersaturated with respect to calcite at both top and bottom of the shaft, although there is a measurable uptake of CaCO3 as the water traverses the shaft walls. The shafts act as aeration chambers, and there is much loss of carbon dioxide from the ground water during movement through this segment of the underground route.

Notes: Gamma logs, by revealing differences in the radiation intensity of unconsolidated sediments, can provide important information on the depth and sequence of beds penetrated by a cased well. In some instances the log of a well drilled into a sand and gravel aquifer can indicate the interval, or intervals, most favorable for screening. Changes in logs made before and after a well is screened and developed can show zones in the screened interval where most development occurred, and provide valuable clues as to the overall effectiveness of development.Although little used at present, gamma logging holds promise of becoming an important tool in hydrologic studies and in the well construction industry. More testing and possibly standardization of equipment is currently needed, along with experimentation in logging techniques, to improve the method. Field correlation between logs and drilling samples are necessary to improve the accuracy of log interpretation.

Notes: A new digital-computer modeling technique uses response curves for discrete regions of a stream-aquifer system to compute the percentage of applied irrigation water and precipitation that recharges the ground-water reservoir. The hydrologic system modeled is a part of the Arkansas River valley in southeastern Colorado. A 150-mile reach of the valley (Pueblo to the State line) was divided into seven smaller reaches. Streamflow, irrigation water applied from canals, ground-water withdrawal by wells, and precipitation data collected during 1964-68 were considered. A wide range of assumed values of recharge from applied irrigation water and precipitation were simulated by the model. The differences between computed and measured changes in ground-water storage were extremely sensitive to the programmed recharge value. Convergence of computed and measured change in ground-water storage values was obtained for most reaches when 20 to 30 percent of the applied irrigation water and precipitation was computed as recharge to the aquifer.

Notes: Artificial recharge from pits, trenches, or basins ordinarily is not considered feasible in situations where a thick layer of slowly permeable material exists near the surface. Results of a field investigation of recharge from an irrigation tail-water pit indicate that pit or trench recharge is feasible under this condition provided that a much more permeable stratum exists above the less permeable one. The more highly conductive layer acts as a subsurface spreading basin which greatly enhances the opportunity for recharge.The potential for recharge from pits penetrating a highly conductive layer underlain by a slowly permeable stratum can be calculated from the results of a simple theoretical analysis which is presented. The importance of subsurface spreading is demonstrated by a numerical example using conditions similar to those encountered during the field investigation. Under these conditions a narrow pit or trench 525 feet long and 10 feet deep has the potential for recharging at a rate of 1 million gpd or about 700 gpm. Subsurface spreading occurs over nearly 10 acres for this case. Evaporation is reduced because the need for spreading the water over large areas on the land surface is eliminated. Since the length of pit perimeter and not the surface area is the important factor for design, the volume excavated can be minimized by constructing long narrow pits or trenches.

Notes: A data storage and retrieval system for hydrogeologic data is designed to produce lithology distribution maps, isopachous maps, and cross sections showing the boundaries and hydraulic characteristics of river alluvium. Emphasis has been placed on selecting and coding characteristics of the alluvial sediments which will facilitate description in terms of hydraulic properties and in a manner convenient for interpretation. The hydraulic properties of fluvial deposits for input to the system are defined based on analysis of core samples and pump tests.A ground-water study, for which this retrieval system was designed, is part of the research being conducted by the Agricultural Research Service in the Washita River valley in south-central Oklahoma near Chickasha. In the ground-water study, maps and cross sections from the retrieval system are used—in conjunction with the hydraulic coefficients and water-level records—to estimate the rate of ground-water flow and storage for selected time increments. This information is needed in the study for developing a mathematical model of surface runoff as influenced by upstream tributary development.

Notes: The hydrogeologic environment adjacent to the sanitary landfill used by the City of Moscow, Idaho, was investigated in an attempt to identify the factors contributing to its alteration and to the reported alteration of ground water downgradient from the fill. The refuse disposal trenches cut through loess and penetrate weathered granite. Field observations and samples from piezometer drillholes showed the major aquifer in the area to be the weathered granite underlying the loess, particularly in the draws. Ground-water samples collected from the piezometers and from a stream downgradient from the landfill revealed that certain aspects of surface water quality are degraded and that shallow ground water is slightly contaminated. However, serious widespread pollution of ground water by the landfill is not in evidence.Electrical resistivity was tested as a means of detecting leachate from landfills in this type of environment. Comparison of resistivity data with water quality data showed that the technique is satisfactory, provided traverses are nearly horizontal.

Notes: Bicarbonate-rich ground waters are present beneath Baton Rouge, Louisiana. They may be subdivided into two subtypes based on the dominant cation. Many ground waters are Na-rich, the others are Ca and Mg-dominant bicarbonate waters. Na/Ca and Na/Mg epm ratios in the Na-rich subfacies are 126-394 and 347-1649, respectively. The corresponding ratios in the Ca + Mg-dominant subfacies are 0.14-0.58 and 0.17-0.58. The HCO3 concentration varies from 77 to, 412 ppm and the total dissolved solids content is usually lower than 500 ppm.The chloride ion is dominant in some chemical analyses of Baton Rouge ground waters. These waters form a separate hydrochemical facies whose origin is not discussed in this report.Multiple regression analyses of the ion distributions and calculated correlation coefficients for ion associations help quantify the distribution of the dissolved species and help to define the proposed mechanisms for genesis of the ground waters. Ion exchange, selective filtration of dissolved constituents, and mixing of surface waters in the aquifers are the primary mechanisms controlling the chemical composition of the ground waters. The occurrence of the Na-HCO3 facies at shallow levels in the area of maximum offtake is especially interesting. This is attributed to the accelerated ion filtration accompanying the high rate of ground-water production.

Notes: Steady-state flow to a single well fully penetrating a confined isotropic aquifer is analyzed. The hydraulic conductivity of the aquifer changes exponentially from a minimum value at the well face to a constant value in the “undamaged” aquifer. An-equation for laminar flow well losses that are due to a decreased permeability in the vicinity of the well is obtained. The well loss depends upon the pattern in which permeability changes. The integral expressing the well loss is evaluated numerically. The results are presented in a graph with nondimensional parameters and could be used for engineering evaluation of the laminar well loss.

Notes: Abstract In 1962, a 2,980-foot deep well was drilled for D. I. Foreman in Middle Castle Creek Valley, Owyhee County, Idaho. This well, which flowed approximately 3,600 gpm, yielded water of 170°F from basalt and silicic volcanic formations; original shut-in pressure was 105 psi. However, leakage began to occur around the casing, and in 1967, a suit was filed on behalf of the Idaho Department of Water Administration to have the well repaired.The Andrew Well Drilling Company, of Idaho Falls, was hired to repair the well, and was on the site in November 1968. Additional casing, packers, and pressure grouting sealed the well adequately. The effect of closure of the foreman well on ground water of the entire area was dramatic. As an example, within 8 hours of closure, water in an observation well 5.7 miles away, rose more than a tenth of a foot. Net increase in this observation well since closure has been 26 feet.

Notes: The principal studies concerned with the ground-water pollution potential from sanitary landfills and dump grounds have been conducted in California, South Dakota, Illinois and England. These studies have all demonstrated that leachates are highly pollutional in characteristics, but once they pass into the surrounding soil regime, the attenuation mechanisms of dilution, adsorption and microbial degradation tend to reduce the impact of this loading on the underground-water supply.A survey of practice in twenty-one States in the United States regarding ground-water pollution from landfill operation showed that not much new research was underway; there was much variation in the code and laws dealing with ground-water pollution; and suggested distances from landfill to water wells varied from 50 to 1000 feet.Finally, based on the literature findings plus the result of the State survey, a set of recommendations are offered to minimize ground-water pollution problems stemming from landfill operations.