ALBERT

Notes: Measurement of the depth to water in wells can be accomplished by timing the fall of a marble or BB. Depth to water can also be determined in terms of the frequency of the reverberations heard in a well. These two methods are called the rock and the bong techniques respectively. Their theoretical basis, their proper execution, and their usefulness are discussed.

Notes: The feasibility of determining the ground-water contribution to stream flow during periods of storm runoff by continuous monitoring of a stream's electrical conductance was investigated. Methods involving graphical techniques or ground-water stage versus base flow rating curves are generally used to determine the ground-water contribution, but the ground-water contribution can also be estimated if stream flow and the conductance of surface water and of ground water are known. The conductance method was tested on a 95-square-mile basin in north-central Illinois. Continuous records of stream flow, stream-flow conductance, and ground-water stage within the basin were collected. A rating curve of base flow versus mean ground-water stage was constructed, and ground-water discharges determined from the rating curve were compared with those computed from conductance data. The conductance method normally gave a lower estimate of the ground-water contribution than did the rating-curve method. However, analyses of storms which were preceded by extended dry periods resulted in much lower estimates of ground-water discharge by the rating-curve method than by the conductance method. The conductance method offers a simple alternative for use in areas where observation wells are unavailable or where rating curves are difficult to construct.

Notes: Observation wells and access holes for neutron probe use were drilled by a jet-percussion drill rig in coarse alluvial material near Tucson, Arizona. The method combines the jetting action which effectively removes loose materials with the percussion necessary to break up tighter formations and large particles. A unique feature of the equipment is the provision for simultaneous drilling and driving the casing to keep the hole open in loose formations. Washed samples of the material being drilled can be obtained from the recirculating water system. Drilling rates were from seven to ten feet per hour, and costs including casing were less than $1.50 per foot. Maximum depth is about 100 feet.Hydrologic study of a ground-water reservoir requires access to the aquifer. Observations are made where the water table intersects the land surface, such as at springs or seeps, or through existing wells. However, wells are not always found in desired locations or are pumped so heavily that their usefulness as observation wells is impaired. Measurements are also made in the unsaturated zone with neutron moisture measuring equipment, which requires a small diameter cased access hole for the neutron probe.An observation well needs a diameter only large enough for access by measuring devices and must be immediately responsive to changes in aquifer water level. For neutron probe use, the required diameter is about two inches, and the well must have no significant effect on moisture movement in the unsaturated zone. To meet these requirements the drilling process should have no lasting effect on the formation surrounding the well. Finally, since the wells have no economic utility, construction cost must be low.A network of observation wells and neutron probe access holes was drilled as part of a project to evaluate the natural recharge from Rillito Creek near Tucson, Arizona. The formation along the creek bed is a coarse alluvial outwash containing almost no clay, considerable running sand, and some large gravel and boulders. Commercial churn (percussion) and hydraulic rotary drills, commonly used for drilling in this area, were first tried but encountered much difficulty in the loose materials.Previous investigators used jetting equipment drill small diameter holes in a variety of alluvi formations (Cederstrom and Tibbitts, 1961; Bowma: 1911; and Pillsbury and Christiansen, 1947). Howeve in most cases, either open hole drilling was used because the fine material content and the limited numb. of boulders or large gravel particles made this methc possible, or drilling mud was used to maintain th hole. The jetting method uses water pumped unde pressure through hollow rods and a drill bit to loose the material and carry it to the surface. The jettin water receives little aid from the drill in loosenin the material to be removed. Usually the drill cutting are settled out in a tank or basin, and the water i recirculated.

Notes: Under steady state conditions of flow, the seepage toward a single gravity well is governed by the Laplace Equation which may be written in terms of either the hydraulic head, the pressure head or the velocity potential. Although this equation is linear, the principle of superposition cannot be applied to sum up the individual effects in the case of a multiple gravity well system due to the variation of the flow domain under the effect of one or several wells. A method is presented allowing the use of the superposition principle in a restricted form. The superposition of the decrements of the base pressure heads than the initial heads before pumping is valid. Also the decrements in the areas of the pressure head diagrams across specific vertical sections than the original areas can be summed up together.The limitations of Dupuit's well formula are explained. The validity of that formula has been proven on the basis of the analysis of the hydraulic forces within the flow medium, an approach which is different than that given by Hantush and Charney. Furthermore, the derived equation is written in terms of the areas of the pressure head diagrams across vertical sections and termed as the Unified Well Formula because it has been proven that the same formula is also valid for artesian wells.The analysis of the hydraulic forces leads to the development of an equation for the free surface. This equation is then solved numerically in one iterative cycle. Due to the lack of simple available solutions, only one case, previously solved by the relaxation techniques, is compared with the presented method. The maximum percent difference in the depth of saturation within 82% of the flow region does not exceed 3.2% whereas in the remainder 18% of the flow region around the well, the percent difference varies between 2.63% to 4.67%. Even these differences do not really indicate actual errors due to the approximation implied in the relaxation method itself using a coarser grid.This distribution of the hydraulic head across a vertical section is assumed parabolic. Although Polubarinova-Kochina presented a mathematical proof which leads to the same conclusion, yet for the reasons explained in the text, the writer preferred to use this type of distribution as a valid physical assumption.The results of the analysis of each single well are applied to determine the pattern of the interference between several gravity wells. By means of the presented approach, the resultant values of the depths of saturation can be obtained on the basis of the explained restricted procedure, of superposition. The hydraulic potential distribution within the flow medium of a multiple gravity well system can also be obtained. The assumption of the parabolic hydraulic head distribution is maintained in analyzing a group of wells. It is recommended to establish a proper computer program covering a grid system that encompasses all the wells and their individual influence regions in a certain well field.In the entire analysis, Dupuit's assumptions are eliminated. However, the two main assumptions in the given analysis are: (a) the parabolic distribution of the hydraulic head across a vertical section within the flow medium, and (b) the elimination of the circumferential velocities. These two introduced assumptions are -i in the writer's opinion – practically valid.

Notes: Carbonate aquifers with highly developed anisotropic permeabilities and other fractured rocks under water-table or semiwater-table conditions present complex hydrologic settings in which to predict the sustained yield of individual wells or groups of wells. Yields of wells in these settings are particularly responsive to the position of the water level and its relationship to one or more producing zones. Often a well's total capacity may be accounted for by one or more openings encountered in drilling which are separated by varying thicknesses of essentially nonproductive rock. A well s yield is determined more by the position of the water table with respect to these openings than to the proportion of saturated rock penetrated by the well bore.A permeability profile must be defined for. these wells along with their available drawdown, and the inclination of water-yielding openings. Permeability profiles may be roughly estimated from detailed driller's logs and caliper logs, and more precisely determined from flow meter surveys; packer tests and by pumping wells after successive increments of drilling or by a combination of increasing casing lengths and extended drilling. Available drawdown is dependent upon the inclination and position of significant water-yielding openings exposed within the bore hole and seasonal variations in the water-table position. In gently dipping carbonate rocks openings may follow bedding planes or selected beds favoring conduit development. Where this is known to be the case, pumping levels may be allowed to approach the top o.f one or another of these zones depending upon which is most productive.Where openings‘are inclined, pumping levels should be kept well above the depth at which the opening was penetrated to minimize the risk of dewatering conduits where they occur higher in elevation adjacent to the well bore compared to where they were penetrated by the well bore, Test holes may be drilled immediately adjacent to the potential production well to define the inclination of individual conduits or wells test pumped when possible at rates sufficient to draw the pumping level to the top of the opening in question. The latter is preferable because reductions in yield can be observed directly as a function of drawdown. To determine available drawdowns in fractured rocks, a permeability or yield profile, the inclination of openings adjacent to the well and seasonal variations in water levels must be known.

Notes: A field experiment has been installed near Firebaugh in the San Joaquin Valley of California to test submergence of drains as a means of denitrification of ground water. Laboratory and field experiments have shown that denitrification occurs in saturated soil where there is ample organic carbon available for bacterial metabolism. Denitrification and dilution of high nitrate ground water were accomplished in the field.

Notes: As round-water research is accelerated and basic data on aquifer parameters become more abundant, a statistical approach to evaluation of the ground-water regimen becomes increasingly useful. One such statistical technique is the fitting of polynomial trend-surfaces to ground-water levels. Barcholomew County, Indiana was chosen as a test site to derive techniques which could give additional guidance in the selection of areas suitable for the development of future ground-water resources.Trend-surface maps and maps of the deviations from the trend-surfaces were prepared from water-level data and evaluated to establish their relationships with the hydrogeologic regimen. A field-testing program was carried out to evaluate aquifer parameters.On the basis of the results obtained from these studies, the following conclusions were drawn:〈list xml:id="l1" style="custom"〉1A mathematically fitted surface may be considered to approximate the water-table or piezomecric surface, and will be sensitive to fluctuations in the ground-water reservoir.2The anomalous areas of the trend-surface represent local effects superimposed on the regional base and may be explained by a particular set of geologic, hydrologie or man-made conditions.From these conclusions, it appears that trend-surface analysis provides a rapid, inexpensive method of delineating attractive areas for detailed ground-water investigations.

Notes: Accurate measurement of static water levels in wells tapping deeply buried aquifers and aquitards at the Nevada Test Site requires evaluation of and correction for several factors exclusive of instrumentation. Both the drilling method used and the depth of the hole at the time of measurement significantly affect determination of the static water level for the aquitards, and frequently these factors preclude head determination in an economically justifiable time. Density of fluid in the drill stem and hole deviation affect the determination of accurate static water levels for the aquifers. In the principal aquifers, in which hydraulic gradients are as low as 0.5 foot per mile, direct measurement of depth to water is preferable to pressure-gage measurements at the aquifer face. Case histories and graphs are presented to illustrate the magnitude of errors that can result when these factors are disregarded.

Notes: The purpose of well screens and gravel packs is to maintain open access within the aquifer ensuring that thorough development of the well is not impeded by sand. Where a well draws on unconsolidated sands and gravels, or other friable materials, the installation of a screen and pack is essential.The use of correctly designed equipment is important and this paper represents a review of the diverse types available, but does not set out to make any recommendations.Well screen designs should incorporate the following features:〈list xml:id="l1" style="custom"〉1Minimum entrance velocity.2Maximum open area of screen.3Correct design of slots to minimize blockages.4Slot size should match aquifer or gravel pack medium.5Screen material should be corrosion resistant.6Screen should allow for periodic maintenance.Commercial well screens fall into various categories according to their slot designs. A slot shape, offering the maximum open area consistent with strength, is a priority and the material used in screen manufacture has an important bearing on this. Blockage of screens may be caused by chemical deposition formed by precipitation or corrosion products, and coated screens have been introduced seeking to inhibit this.Gravel packs should include the following design features:〈list xml:id="l2" style="custom"〉1Sand free operation after development.2Give lowest possible resistance to permeation.3Offer low entrance velocities.4Be resistant to chemical attack and have an efficient service life.The gravel pack should ensure that the completed well operates free of sand; thus the particle size of the pack depends upon the particle size of the aquifer. Gravel pack design should be guided by standard sieve analysis.It is evident from the variety of claims made for well screens and gravel packs that further research is necessary. It is suggested that the following points need further investigation:〈list xml:id="l3" style="custom"〉•. Improved design of nonblocking opening.•. Design consideration of screen resistance to chemical attack.•. Best type of gravel and optimum thickness of the pack.•. Head loss through the screen and pack.

Notes: Theoretical analyses predicted and experimental observations—confirmed a mechanism by which strong capilary forces hindered instead of helped promote infiltration into soils. Infiltration into an unsaturated soil overlying an impermeable barrier displaces the air from the soil interstices. Unable to escape downward, the air may escape upward in bubbles travelling through large pores, or, if the pores are small and the capillary forces are large, the air is compressed between the wetting front and the barrier. This reduces the infiltration rate and may result in an almost stable wetting front. Under certain calculable conditions the air pressure build-up is sufficient to cause sudden localized horizontal rupturing of the soil at the wetting front and to lift it along with the infiltrating water, forming a cavity. The air-filled cavity breaks the flow passages and percolation ceases through pores terminating in the cavity. Observations with soil columns have shown that when provision was made fot the displaced air to escape less than one minute was required for the wetting front to move three inches; when the air was not free to escape and the soil raptured, two weeks were required for the wetting front to move this distance. Grain size and packing play a role by limiting the capillary pressure build-up and the bubbling pressure. This phenomenon should emphasize precautions to be followed in applying laboratory infiltration results to engineering predictions of field conditions.

Notes: The minimum probability that: anomalous bulges and re-entrants produced by mechanical (as opposed to interpretational) contouring of data on maps actually exist and are not merely the result of measurement errors may be calculated. The calculation consists of computing the compound probability that the value of at least one data point within each anomaly is actually higher or lower than the value of one data point on each flank of the anomaly. The calculation requires multiple data values at one or more locations on che map or a subjective estimate of the variance of the data. It is assumed that the variance of the data does not change from place to place on the map and that the recorded data values are normally distributed about the true value.

Notes: Studies of limestone hydrology have largely ignored the possible significance of water not flowing in major conduits. This component is designated “percolation water.” The importance of percolation water in an area is probably a function of rock type, structure and hydrologic characteristics. Experiments undertaken in England and Jamaica tracing percolation water with the dyestuff Pyranine Conc. suggest longer flow-through times than for water sinking at discrete points on the surface (allogenic water). The soil cover in an area may be in part responsible for this delay. Results from percolation water traces may be used to compile isochronal maps of limestone catchments.

Notes: For several years resistance-capacitance networks have been used to simulate aquifers. Most reported work has been concerned with fast time analogues in which the period under consideracign is represented in micro-seconds. However the alternative slow time analogue has many advan tages since the electrical experiment takes several seconds. This results in simpler equipment and simpler experimental techniques.The paper concentrates on the practical aspects or the slow time analogue giving details of the components, describing a method of simulating wells and recharge and comparing measuring instruments. The techniques are illustrated by a simplified example.

Notes: Insights into the chemical and Hydrogeologie history of spring waters in carbonate rocks can be gained from a study of the chemical quality of such waters and of the waters which feed springs. The median Ca2+/Mg2+ ratio was 3.4 in 29 spring waters from folded and faulted carbonate rocks near State College, Pennsylvania, indicating ground-water flow predominantly in limestone. The mean dissolved oxygen content was 7.7 mg/1 or 71% of saturation consistent with subsurface flow chiefly under water table conditions. Most of the dissolved solids (as specific conductance) including pollutants such as Cl and NO3 were added to spring waters during ground-water flow. Specific conductances ranged from 180 to 476 micromhos, with a mean of 347 micromhos. CO2 pressures were from 10−1.9 to 10−2.6 atm with a mean of 10−2.2. atm. The CO2, which is chiefly introduced as gas by downward diffusion from the soil zone, gives spring waters the capacity to hold about 3 times more hardness and alkalinity than streams in equilibrium with the atmosphere. However, all spring waters were undersaturated with respect to calcite and dolomite because of their short residence times as ground water. Dye tracing of ground-water feeding springs in two drainage basins gave residence times of 2–6 days for subsurface flows of about 4,000 feet. The specific conductance and carbonate saturation data indicate that ground-water residence times of the 29 spring waters average somewhat longer than 2–6 days.

Notes: Reliable prediction of the yield of infiltration galleries can be made only on the basis of careful field testing combined with evaluation of surface flow-duration data. While extensive pump testing is often relatively expensive the information obtained indicates the long-term utility of the system. Pump test procedures and methods of analysis are outlined.With proper design much wider utilization can be made of infiltration galleries than is presently done. The long life and low maintenance requirements are particularly favorable for small systems. Design and maintenance suggestions are made for successful operations.

Notes: In the Maumee River Basin of northwestern Ohio the principal source of ground water is the Silurian-Devonian carbonate aquifer. The use rate of ground water from this aquifer could rapidly increase many fold in the near future. This situation demands quantitative information on the resource potential of the aquifer, if proper development is to be encouraged.A relationship between ground-water use and recharge rates through an analysis of the cones of influence is demonstrated in this paper. Computed recharge rates for the cones of influence vary from 6,800 to 75,300 gpd/sq mi, and the variation is systematic in that the higher recharge rates correlate with the higher pumpage rates. Recharge rates appear to have an upper limit of approximately 100,000 gpd/ sq mi, which corresponds to a maximization of the vertical hydraulic gradient. Although maximization of the vertical hydraulic gradient is impossible to achieve for a given cone of influence, it can be approached by lowering the piezometric surface of the aquifer by increasing the pumpage rate.Assuming that the safe yield of an aquifer is equivalent to the rate of recharge, this study demonstrates that development of an aquifer can increase many times its potential.

Notes: An extensive program of electric well logging has been conducted in Hawaii during the past three years to determine the applicability of this tool to the volcanic environment which exists in Hawaii. Electric well logging techniques were found to be useful in Hawaiian basaltic aquifers; however interpretation of both spontaneous potential logs and resistivity logs varies from the conventional interpretation of electric logs in sediments. The interpretation of fluid conductivity logs in Hawaii follows conventional water well techniques.The analysis of spontaneous potential and resistivity well logging in basalts, which constitute most of the Hawaiian aquifers, poses problems because of the relatively uniform composition of the basalts and the complex relation of porosity to resistivity in basaltic aquifers, and because logging usually is performed in water-filled boreholes. Spontaneous potentials are thought to result primarily from fluid flow rather than from electrochemical potential, and positive SPs generally indicate zones with flow from the aquifers into the well, and negative SPs generally indicate zones with little flow or flow from the well into the aquifer. Resistivity logs indicate the location, number, individual thickness, and total thicknesses of permeable and less permeable formations, and are useful as indicators of water-yielding zones. High resistivities generally are indicative of dense impermeable basalts and low resistivities are indicative of porous permeable zones most likely to contribute water to the borehole. Both resistivity and spontaneous potential logs provide a direct measurement of depth to water, depth of casing, and depth of hole.

Notes: The salinity and nitrate content of well water for an urban zone (Fresno-Clovis, California) and the immediate surrounding irrigated agricultural zone were compared using data for 1950 through 1967. Time trends in these water chemical properties were evaluated statistically by dividing the 18-year period into three 6-year periods. Salinity of the urban zone ground water has increased with time, whereas that of the agricultural zone has fluctuated considerably. Possible reasons for changes are discussed. The nitrate content of well water from both zones has increased with time, with water from the agricultural zone showing the greatest increase. Key words; ground-water degradation; salinity; nitrate.

Notes: A break in a waste-discharge line associated with a 49-foot rise in stage of the Ohio River in March 1967 allowed an undetermined volume of 22 percent hydrochloric acid to enter the Pleistocene outwash aquifer used by a Kentucky industry. Chloride concentrations in excess of 30,000 mg/l (milligrams per liter) were observed in the water discharged from the industrial well nearest the break in the waste-discharge line. Chlorides ranged from 5–26 mg/l in water pumped from this area prior to intensive development. Other changes in water chemistry such as an increase in iron from 5 mg/l to 9,600 mg/1 indicate a dissolution of the aquifer materials. Movement of the highly mineralized water in response to river stage and pumping of the industrial wells has forced the industry to change its water-supply system. Three wells, approximately 600 feet from the river, were the primary water source prior to March 1967. By March 1968, the well nearest the acid source was abandoned, the remaining two wells near the river were used in a supplemental capacity and a fourth well 1,500 feet from the river plus a new well were the primary water sources. Fluctuations of chlorides in an industrial well near the river for a 16-month period indicate a persistent body of highly miner alized water near the acid source. Movement of this water body appears to be regulated at low river stages by the inclined surface of the New Albany Shale bedrock.

Notes: This paper deals with the ground-water flow into a drilled well, consisting of a vertical shaft and radially spaced horizontal intake pipes.It is based on model tests, devised and executed by the author in the Hydraulic Laboratory of the Haile Selassie I University in Addis Ababa, Ethiopia.The author tested the assumption of linearly distributed inflow into the pipes, based on the steady-flow theory of Darcy-Thiem, and found satisfactory agreement between theory and experiment.

Notes: A research project “Hydrologic and Other Aspects of Water Laws in Minnesota,” was conducted by the authors during the period July 1, 1967 through June 30, 1969 (see Walton and others, 1968, and Haik and others, 1969). The project was supported by funds provided by the U. S. Department of the Interior as authorized under the Water Resources Research Act of 1964 (Public Law 88–379).The project was concerned with: a compilation and analysis of the numerous codified and uncodified legislative laws, major court decisions, federal legislation, and ordinances of villages and cities bearing on water and related land resources in Minnesota. This paper briefly summarizes, without citation, the results of the research and presents the authors' views on the following subjects: state water resources administration, water policies as expressed in Minnesota's laws, problems associated with differing scientific and legal classifications of water, conflicting objectives of major resource agencies, provincialism and precedent in court decisions, insecurity of existing water rights, the adequacy of current legislation regulating water permits, the adequacy of the existing riparian doctrine of water rights, conflicts of federal-state jurisdiction, and constraints on development and management of water and related land resources in Minnesota.

Notes: The engine of a field vehicle can easily be used as an air pump by inserting a commercially manufactured check valve into a spark-plug socket. Small-diameter piezometers can be pumped with compressed air from this source. With sufficient air-line submergence, the air lift method can be used to pump 1-inch diameter piezometers where the pumping lift is less than 70 feet and 1.25-inch diameter piezometers where the pumping lift is less than 50 feet. In cases where this method will not work, some of the water contained in a piezometer can be pumped out by pressurizing the piezometer if the formation transmissivity is low and the pumping lift is not excessive. The maximum pumping lift is a function of the rate at which pressure in the piezometer is increased and the rate at which water flows into the formation with increasing head in the piezometer.The engine air pump is useful in developing piezometers, flushing out stagnant water before taking water samples, obtaining water samples, and creating head differences to initiate slug tests.

Notes: Increased irrigation demands on water from the Platte River in central Nebraska are causing a depletion in the flow that passes the City of Lincoln's Municipal well field, at Ashland, Nebraska. A study was made for the U. S. Army Engineers, Omaha District as to the future harmful effects of this depletion.a mathematical model using the Theis nonequilibrium equation was formulated. Drawdown computations were performed using an IBM 360 Model 65 computer. Recharging image wells were used to represent the physical boundary of the aquifer. Drawdowns in selected wells were calculated using the method of superposition by including both the real wells and the image wells. Values for permeability and the storage coefficient were computed from field pumping test data.Three different model runs were made. First, the wells were assumed to be pumped continuously at maximum output of 84 M.G.D. for periods of 10, 30, and 60 days both with and without river recharge.Next, the same time periods and recharge situations were run assuming 37 wells to be operating at their present field capacities, totaling 60 M.G.D.The third computer run was made using 39 wells. During the first 10-day period only 27 wells were modeled to produce 51 M.G.D. In the next 10 days 31 wells were required to produce 59 M.G.D., and finally for the last 10 days 20 wells were-used to produce 37 M.G.D. This operation duplicated the actual operation for July, 1968, when the all-time peak production for any one month was recorded.It is concluded that the well field can be operated at high rates for periods of greater than 30 days without recharge from the river. Previous studies have indicated the river is the source of most of the water produced from the wells. The study does indicate that the well field can draw on the ground-water reservoir for much longer periods than had been assumed in the past.

Notes: Acid mine drainage is a serious problem in the Appalachian region. Coal mining has disturbed the natural ground flow system. The mines are continuously being flushed by this disturbed flow system and producing enormous quantity of sulphuric acid. A study of McDaniel Mine has revealed that the flow is lateral and clay layers under the coal do not allow it to leak into the underlying aquifer. A study of water well logs within 10 miles of Todd Mine revealed the existence of three separate aquifers. A pilot plan for Todd Mine is proposed to discharge the uncontaminated water from the upper aquifer to the lower aquifer under the concept of “weeping wells.” The acid discharge from the mine may be stopped. The extension of this scheme may solve the serious problem of pollution of Lake Hope. The concept may further be extended to other areas of the Appalachian region to control acid mine pollution.

Notes: A technique is presented for simulating partially penetrating rivers on two dimensional resistance-capacitance network analogue aquifer models. The method is tested against an analytic solution due to Boulton (1942). Several results are presented which can be used to estimate an approximate value for the steady state discharge of a well pumping near to a partially penetrating river.

Notes: This report is the result of a request by the State Board of Examiners of Water Well and Pump Installation Contractors. The Board is in the process of formulating a more reasonable set of guidelines which control the location of wells designed to produce water for human consumption and/or food processing with respect to potential or existing sources of ground-water pollution.The pollution of ground-water supplies is artfully treacherous. It appears belatedly and often is not recognized until a relatively large area has been contaminated and perhaps one or more individual water supplies have been rendered unfit for human consumption. It is known that soils and aquifer materials have capacity to remove or “filter” some types of contaminants, and something is also known of the limitations in this regard. It is with these thoughts upon which this report is based. The report is designed to briefly describe the results of several pertinent ground-water pollution investigations and present current and potential standards for governing “safe distances” between domestic-food processing wells and sources of potential or existing pollution. The recommendations are meant to emphasize the fact that no one set of distances are adequate and reasonable for ALL conditions. Whenever possible the “safe-distance” between a subject well and a source of potential or existing pollution should be based on local conditions.It is important that we develop knowledge that will permit continued use of the soil mantle as a waste-water treatment system and at the same time permit continued use of ground water for human consumption and/or food processing. Functional legal, administrative and engineering mechanisms must be developed to maintain this combined usage.The Colorado Board of Examiners of Water Well Drilling and Pump Installation Contractors was established in early 1968. By October the Board adapted a set of rules and regulations which provide minimum standards for location, construction, modification or repair of pumping equipment.The Board's current concern is with the sanitary quality of those waters which are to be used for domestic purposes; in particular. human consumption. Realizing that proper sanitary protection of domestic wells involves the prevention of the intake of contaminants, the Board of Examiners introduced a set of standards which provides for the location of wells and well casings with respect to sources of contamination. The standards were chosen arbitrarily and do not consider the differences between chemical and biological contaminants.It is the purpose of this report to briefly point out some of the past and current developments regarding the nature of ground-water pollution and, in particular, data related to studies of the length of travel of bacteria and virus-laden water when injected on both soil surfaces and in water wells.Two distinctly different aspects of pollution travel are considered. They are: (1) the movement of bacteria and viruses downward with percolating water; and (2) the lateral movement of identical pollutants once they have reached the zone of saturation.

Notes: Seismic methods, combined with available well and geologic data, were used to define the subsurface hydrologic and geologic conditions of the Walnut Gulch Experimental Watershed, a deep, alluvial basin near Tombstone, Arizona. Surface geology of the valley indicates an alluvium-filled area between igneous intrusives and sedimentary rocks that support the Tombstone Hills on che southwest and the Dragoon Mountains on the northeast. Seismic determinations revealed depths to the water table ranging from near zero at the confluence of Walnut Gulch and the San Pedro River to 475 feet in the central portion of the watershed. The accuracy of predicting the depth to either ground water or basement was ± 6 percent, while that for ground water alone was ± 10 percent.Seismic refraction methods failed to produce satisfactory results when certain conditions or combinations of conditions existed. The great depths of alluvium created the problem of estimating the seismic traverse length necessary to accurately determine the alluvium-basement interface. Increased compaction of alluvium with depth causes additional interpretation difficulties in some areas. Also, water-table elevation may not always be accurately determined if it is located above, and close to, a highervelocity layer.A minimum of gravity or well log information greatly increases the reliability of seismic information in these problem cases. Other methods may still be necessary to substantiate the seismic data obtained under these conditions.

Notes: Two stable finite difference schemes are presented for the numerical solution of the nonlinear partial differential equation describing the radial flow of soil moisture. The nonlinearity is due to the fact that the soil moisture diffusivity, D, is a nonconstant function of the nondimensional soil moisture, y. Numerical solutions for twenty-one different moisture dependent diffusivities are obtained. These diffusivities have the following forms: (a) eleven of the diffusivities represent flow into a sink, and the other ten represent flow from a source; (b) D is proportional to yP, where p =¼, ⅓, ½, 1, 2, 3, 4; (c) D is proportional to Ay, where A is a positive constant; and (d) some of the D's possess inflection points as y varies from 0 to 1. From these numerical solutions quantitative results are obtained for the following: (1) the boundedness and monotonicity of the moisture distribution; (2) the continuous dependence of the moisture distribution on the system's parameter, namely, the diffusivity; (3) the rate at which the “wetting front” approaches the steady state solution; (4) the evolution of the moisture front with time and with the formulation of the diffusivity; and (5) the time evolution of the rate of inflow or outflow at the wall of the source or sink.

Notes: The knowledge of aquifer parameters is invaluable for quantitative description of geohydrologic systems and for optimal utilization of ground-water resources. The classical methods of pumping-test analysis are mostly graphical in nature and there is room for error in individual judgment in the geographical analysis. The computer method for aquifer evaluation comes under the inverse analysis techniques and is based on the classical principle of least squares. The sum of the weighted squares of differences between the observed drawdowns and the drawdowns calculated using the theoretical drawdown equations for the flow system under consideration is minimized, treating the aquifer parameters as decision variables. The method can be applied to any flow system for which analytical expressions for the potential distribution are known. The method was successfully applied to four pumping tests, two in nonleaky confined flow 1 systems, one in a leaky confined flow system, and one in an anisotropic nonleaky confined flow system. The percentage differences between the values of storativity and of transmissivity arrived at by the two methods are found to be as much as 24-and 1.6 percents, respectively.

Notes: Alluvial faults are generally treated as impermeable boundaries. Recent investigations of the faults in Califoria's Owens Valley, however, reveal that they are semi-pervious, or leaky in nature. The rate of ground-water movement through a semi-pervious alluvial fault is dependent upon the hydraulic conductivity of the fault gouge, the thickness of this zone, and the water-level differential across the fault. Optimization of the ground-water resources in the Owens Valley is currently being practiced using these faults in a controlled RECHARGE-EXTRACTION-SALVAGE System. In a system of this type, artificial recharge is induced into the Valley's aquifers upgradient from alluvial fault zones by impounding and diverting the creek flow tributary to the area. Extraction of ground water is effected by means of large-diameter supply wells located near the faults on the upstream side. Salvage of ground water is accomplished by lowering the water table in the vicinity of these faults, thereby causing phreatic growth to die out. When predicting water levels in the vicinity of semi-pervious faults, a solution is obtained for the induced water-level decline caused by backward leakage through the faults.

Notes: The true velocity, V, of ground water at a point in the ground-water system may be expressed as the sum of a number of partial velocities labeled V1, V2, V3, et cetera. Each partial velocity may be denned as a velocity which results from the presence of certain features of the configuration of the water table. Partial velocities may be used to facilitate the discussion of ground-water flow systems and associated phenomena.

Notes: This paper presents some of the more common errors made in the development of ground-water supplies in the alluvial aquifers along the Ohio River in Kentucky. Ample available literature on proper methods of development of the alluvial aquifers generally seems to have been ignored by the water users in the area. The more common errors made in the typical developments are singled out for discussion.In the typical development the aquifer is treated as an inexhaustible underground river. Wells generally are clustered in small areas remote from the Ohio River, and are likely to be located more for convenience and economy of pipeline or property access than for hydrologic considerations. It is hoped by highlighting these errors and showing alternative methods of development that proper development practices will be fostered.Stages in the development of two hypothetical groundwater aquifers in the Ohio River valley are shown by eight illustrations that stress the common errors made in development and alternative methods of development taking into account hydrologic considerations.