ALBERT

Notes: The tidal efficiencies of wells tapping the principal artesian aquifer in Glynn County, Georgia decrease with distance from the influencing tidal body and also decrease with well depth. Although the magnitude of water-level fluctuation of these wells is largely dependent upon the distance to a large tidal body, the time of a high or a low water level in the wells is mainly dependent upon the time of a high or a low tide in a small, nearby tidal body. A modified formula for computing tidal efficiency is developed:〈displayedItem type="mathematics" xml:id="mu1" numbered="no"〉〈mediaResource alt="image" href="urn:x-wiley:0017467X:GWAT24:GWAT_24_mu1"/〉 From this formula, tidal efficiency can be calculated rapidly and easily

Notes: Coarse granular deposits in preglacial river valleys are an important source of ground water on the Canadian prairies. Such an aquifer can commonly be modeled by an infinite-strip leaky-artesian aquifer. Test results can be analyzed, future drawdowns predicted, and safe yields estimated by applying the standard leaky-artesian formula in conjunction with image-well theory, making due allowance for well-loss factors.This paper develops basic formulas required for safe yield estimation for an array of n wells located on the axis of an infinite-strip leaky-artesian aquifer. In general, determination of safe yield for each well depends on the solution of n simultaneous linear or nonlinear equations. For certain symmetrical arrays, however, the number of equations to be solved is approximately halved. A linear equation will apply for any well if flow adjacent to the well bore always obeys the Darcy law for all pumping rates of interest. If all n equations are linear, they may be solved by the methods of matrix algebra; if not, a trial-and-error solution must be adopted.The method is illustrated by an application to a 6-mile stretch of a buried-valley aquifer near Edson, Alberta. The numerical coefficients in the system of equations are first derived and the equations then solved to obtain estimated 20-year safe yields for well arrays containing up to 38 equally spaced wells.

Notes: The horizontal viscous flow model with “infinite” areal extent can be used for almost any well flow problem whether two-dimensional or three-dimensional, steady or nonsteady, single aquifer or multiaquifer. This model can also be used in the field of soil mechanics for subsurface drainage problems. The design includes scale model analysis and the application of conformal mapping techniques in order to simulate an ideal aquifer. Construction, calibration, and test procedures for the model are described. The apparatus has proved to be both a valuable research tool and an excellent teaching aid.

Notes: Procedures are developed and charts are presented to determine the unsteady drawdown in a group of wells which are located along a straight line and fully penetrate a homogeneous, isotropic, artesian aquifer. Based on the linearity of the governing field equation, the principle of superposition is used to combine the effects of individual wells, and solutions are obtained by using a digital computer to evaluate an exponential integral. The concepts of equivalent radius, coefficient of interference, and degree of uniformity are introduced, and quantitative graphical relationships are given as functions of the independent variables, which are the number of wells, well spacing, and time.

Notes: A reconnaissance of parts of the former West Aden Protectorate enables a characterization of the dominant hydrologic elements to be made. In this desert environment intermittent streams from the east-west range of mountains provide considerable water for flood irrigation and groundwater recharge of alluvial fans along the Gulf of Aden. High yield wells are developed in the coastal area and in at least one alluvial area on the back slope facing the Empty Quarter. Ground water in the interior is generally restricted to areas where wadi flow provides occasional recharge. Relatively few rock wells have been drilled in the area. Many wells in the alluvium yield silty water leading to clogging of the wells and undue pump wear.

Notes: The economic potential of the Mekong Delta is largely unrealized because of the harmful effects of uncontrolled flows of surface water which occur generally during the period August-October. Interest in the Delta by various government agencies has resulted in preliminary plans for redistributing surface waters to control flooding, facilitate drainage, provide for irrigation, and prevent sea-water encroachment. Current estimates indicate that construction costs in excess of a billion dollars would be required to develop an initial 2.1 million hectares (5.2 million acres) of the Delta to maximum economic potential; these costs do not cover those for upstream projects upon which the Delta developments depend.The Mekong Delta is underlain by an upper section of Recent alluvium, and a lower section of older alluvium. The older alluvium contains a permeable artesian zone called the 100-meter aquifer, which is the most productive groundwater reservoir in Viet Nam. Tested well capacities range from about 145 to 635 gallons per minute (gpm); more efficiently designed wells should produce in the range of 500 to 1,000 gpm from this aquifer. Part of the 100-meter aquifer is intruded by sea water.Current data permit no more than speculation with regard to storage, recharge, and flow in the 100-meter aquifer. Storage is estimated to be approximately 30 million acre-feet in the lower Delta, where the total dry season irrigation requirement is about 1.2 million acre-feet. Piezometric levels in the Delta wells may be due merely to sea-water pressure gradients acting across a horizontal saline-fresh-water interface; they do not necessarily imply ground-water flow or an area of recharge.A major inconsistency exists in the relation of certain reported piezometric levels and corresponding depths to well intakes assuming conditions of either hydrostatic or hydrodynamic equilibrium, and it is necessary to postulate special circumstances to account for this. The data also indicate conditions conducive to subsidence, although no evidence for subsidence has yet been observed.The most feasible plan for development of the Mekong Delta may involve the conjunctive use of surface water and ground water of the 100-meter aquifer, even though induced recharge and a ground-water barrier against sea-water intrusion might be necessary. Storage capacity is adequate, but more information is needed on recharge and total obtainable well capacities for the 100-meter aquifer and on the possibilities for occurrence and control of subsidence in the event of widespread ground-water development.

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: One of the deepest water-exploration wells in the southeastern United States was completed in 1966 at Jacksonville, Florida. It was drilled to a depth of nearly 2,500 feet to supply geologic and hydrologic information on the deeper unexplored part of the Floridan aquifer. This aquifer consists of a series of water producing zones separated by nonproducing zones. An important new fresh-water producing zone was found, and the contact between the fresh water and salt water was located. The well was completed in three separate zones so that it could be used to monitor the the deeper part of the aquifer to detect any salt-water encroachment. This paper describes the objectives, techniques, and results of drilling the test well.