ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1983.tb01937.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

ABSTRACTDue to characteristics of centrifugal pumps, most pumping tests in large‐diameter wells exhibit a decreasing abstraction rate with increasing drawdown. Type curves are obtained for the case of abstraction rates which are functions of the well drawdown; values for the type curves are obtained from a numerical model. For the case of constant abstraction, these curves provide an alternative to the classical approach. By plotting the ratio of drawdowns at different times, it is possible to identify more easily when the aquifer begins to contribute to the well discharge. The practical application of the technique is illustrated by a field exampl

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1983.tb01938.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

ABSTRACTSurface Impoundment Assessment (SIA) is a methodology for determining the potential for ground‐ water contamination from pits, ponds and lagoons. SIA produces a numerical rating of a site, based on the sum of scores assigned to four categories: vadose zone properties, ground‐water availability, ground‐water quality, and waste characteristics. The SIA for New Mexico was conducted as part of a nationwide survey of potentially hazardous waste‐disposal sites. Comparisons of the contamination potential scores and observed ground‐water contamination from mining, milling, and industrial impoundments in New Mexico using histograms, Mann‐Whitney U‐Test, and linear logistic regression indicate that vadose zone properties and the nature of the waste contribute most to the general success of the SIA method to predict contamination. The remaining two categories which rate ground‐water availability and natural ground‐water quality do not appear to be reasonable measures of ground‐water contamination potential. Rather, these categories are more indicative of the value of the gro

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1983.tb01939.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

ABSTRACTRecent drilling for natural gas in the Glaciated Appalachian Plateau area of northwestern Pennsylvania has caused limited, but increasing ground‐water contamination. By evaluating hydrogeologic parameters at a proposed gas well site, such as the ground‐water flow system, permeability of surficial sediments, and the presence of fracture zones, the contamination hazard of the site can be assessed. Three case studies document that the most hazardous sites are generally located on or near valley walls of major drainageways. The relatively steep hydraulic gradient, the frequent presence of highly permeable surficial sediments, and the low to moderate dilution of contaminants along the intermediate‐length flow paths at these sites all contribute to a relatively high pollution hazard. In addition to locating gas wells in high‐hazard hydrogeologic zones, allowing the annulus of gas wells to become pressurized is the other major factor contributing to aquifer contam

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1983.tb01940.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

ABSTRACTNonpumping monitoring wells are commonly installed and sampled to delineate the extent of a contaminant plume and its chemical character. Samples from municipal and private pumping wells are frequently collected during ground‐water contamination investigations as well. Pumping wells are also employed for remedial actions.To properly interpret sampling data from monitoring and pumping wells and to estimate their potential effectiveness in remedial actions, it is important to clearly define the geometry of that portion of the aquifer contributing water to the well (the capture zone). Velocity distribution plots by manual and computerized methods are illustrated and shown to be simple and of reasonable accurac

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1983.tb01941.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

ABSTRACTMany hydrologists have observed that dispersion coefficients, when measured in the field, turn out to be scale‐dependent. That is, the greater the travel distance in a tracer test used to measure dispersivity, the larger the dispersivity value that is calculated. Recently, Güvenet al.(1983) presented a study which contains a basis for understanding the phenomenon of scale‐dependent dispersion within a deterministic framework. The results of that study are used as a basis for defining a scale‐dependent macro‐ dispersion coefficient for unidirectional flow in a stratified aquifer. Theoretical expressions are then obtained for the macrodispersivity, its various components, and its small time and large time limits. Using the data of Pickens and Grisak (1981a, b), numerical values are calculated for the macrodispersivity, and estimates are made of the travel distance required in order to reach Fickian conditions. Asymptotic large time macrodispersivity values of 49.5 m to 990 m and travel distances of 5.4 km to 109 km result for the particular aquifer studied. Based on these results it appears that Fickian conditions will seldom apply in practice to porous media flow. This study and previous studies show that the primary physical mechanism that causes spreading of a solute near the source is different advection rates at different elevations in the aquifer. Present results and comparisons with field data indicate that this phenomenon is not represented well by a scale‐ dependent dispersion coefficient. In modeling dispersion phenomena, it appears that more emphasis should be placed on field study and the accurate determination of hydraulic conductivity variations and other nonhomogeneities, and less on incorporating somewhat arbitrary dispersion coefficients into complex mathemati

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1983.tb01942.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

ABSTRACTWarm Springs Valley, located in northwestern Virginia, is characterized by the discharge of springs from cavernous limestone at temperatures up to 40°C, although the measured geothermal gradient is a normal 10°C/km. The area is therefore hypothesized to be an important example of a situation where thermal convection is sufficient to produce high‐temperature surface waters. A finite‐difference numerical model was constructed to simulate the simultaneous transport of heat and fluid under combined forced and free convection conditions. This model was used to test the hypothesized heat flow system for Warm Springs Valley.The results of the testing show that, within the hydrogeological constraints found at Warm Springs Valley, convection with a normal geothermal gradient is capable of producing 40°C hot springs. The conditions required a zone of enhanced vertical hydraulic conductivity in the area of ground‐water discharge and a deep zone of enhanced horizontal hydraulic conductivity. The enhanced zones are consistent with the geology found in t

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1983.tb01943.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

ABSTRACTA two‐dimensional finite‐difference computer code was used to model the ground‐water flow system in an alluvial basin in southwest New Mexico. A three‐step approach was used to determine the transmissivity distribution for the model. First, values of the natural logarithm of transmissivity (In T) were interpolated from existing data using the kriging technique. This interpolation scheme also produced a map of standard deviations of the kriging errors. Second, a conventional flow net was drawn from steadystate water levels with the aid of the kriged hydraulic head distribution. Third, the approximate transmissivity map, the standard deviation map of the kriged In T values, and flow net were used to select the segment of each streamtube where transmissivity was known with greatest certainty (smallest In T kriging error). Then, transmissivities in other segments of the stream tubes were calculated from Darcy's Law. This distribution, when input to the numerical model, did not have to be altered appreciably during the calibration for a steady‐state and seven‐year transient period. Most of the transient calibration was accomplished by adjusting storage coefficients. Considering the uncertainty in the available pumping data, very good agreement was found between observed and predicted water levels during a four‐year model verifi

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1983.tb01944.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

ABSTRACTLaboratory investigations have been carried out on one‐ and two‐component artificial sand samples in order to estimate the relations between formation factor (F), porosity (φ), and permeability (K). The measurements were carried out by varying grain size and size distribution while keeping constant shape and packing; in our experimental conditions the measured formation factor approximated the intrinsic formation factor.The relationship between formation factor and porosity (F = a ·φ−m) is independent of grain size and size distribution; the coefficient values are: a = 1·15, m = 1·42.The relationship between permeability and formation factor has the general form K = r · F−s, where s is constant, and r is a function of the mean size d of the small component of the samples.The K‐F relation can be established only if d is constant; in these conditions the relationship is an inverse one, and the negative trend is related to the variations in si

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1983.tb01945.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract.The discharge in pumping tests conducted on large‐diameter wells declines with the fall of water level. This violates the basic requirement of pumping tests that the discharge should remain constant. A simple device to keep the discharge constant has therefore been developed. This device is also useful in keeping the discharge much lower than the rated capacity of the farmer's pump, and thus in increasing the total test period.The discharge from the farmer's pump is released in a barrel having a V‐notch at the top and an arrangement for returning a part of the discharge to the well. The return flow is gradually reduced through a control valve, and thus the net outflow is kept constant.This device has been used for conducting pumping tests on several dug we

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1983.tb01946.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY