ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1987.tb02880.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

ABSTRACTThe hydrogeology and chemical quality of the shallow ground‐water regime at a coal fly ash landfill was investigated near Montpelier, Iowa. An embankment dam retains the two‐hectare deposit of silt‐sized alkaline coal fly ash in an upland ravine. The fly ash landfill was operated between 1964–;1973 and was subsequently capped with a thin loess layer and seeded to pasture. The ash is underlain by loess, over clay‐rich till, over sandstone. Ground water now saturates the lower one‐half of the ash.Nineteen shallow monitoring wells were installed around and within the landfill. Sampling in 1983–;1984 was conducted for water levels, temperature, pH, alkalinity, specific conductance, calcium (Ca2+), magnesium (Mg2+), sodium (Na+), potassium (K+), sulfate (SO42−), chloride (Cl−), arsenic (As), and selenium (Se).Calculated ion balances for 30 analyses had an error of less than 4%. Native loess‐derived ground water of a calcium bicarbonate type enters the landfill, and then shifts to a calcium sulfate type. A distinct leachate plume presently extends at least 46 meters downgradient from the landfill, passing under and through the dam, then discharging into a small pond. SO42−and Se concentrations in the plume exceed EPA drinking‐water standards, and trace As was detected.Although ground‐water pH increased after entering the landfill, bicarbonate alkalinity declined. Results of equilibrium solubility calculations suggest that this condition evolved from calcite supersaturation within the landfill, precipitating calcium carbonate. Dissolution of calcium and magnesium oxides on the glassy fly ash spheres sustains the highly a

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1987.tb02881.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

ABSTRACTSimilarity of ground‐water hydrographs in karst aquifers with surface runoff hydrographs indicates that some models used in unit hydrograph analysis could adequately model the ground‐water system. Two such models are used to model ground‐water levels in a karst aquifer. The aquifer was treated as a linear time‐invariant system with a response function representing the rise in ground‐water levels in response to rainfall. Two discrete parametric models, the Nash and Muskingum, were tested as response functions. Parameters for both models were identified from one year of data by applying the theory of moments to sets of input and output data. The models were verified using rainfall and water‐level data for a second year. The Muskingum method did not adequately model the system. Results of the Nash mode

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1987.tb02882.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

ABSTRACTThis paper examines the politics of ground‐water management reform in Oklahoma. It argues that the geographic distribution of water supplies and uses significantly modifies the distribution of costs and benefits of reform among political constituencies. Effective restrictions on ground‐water withdrawals would raise large and immediate threats to irrigators and farm communities dependent on irrigation in western Oklahoma. Municipal and industrial water users, concentrated in eastern Oklahoma and reliant on more plentiful surface‐water supplies, would receive more diffuse, longer‐range benefits to management reform. These effects have significant implications for the politics of ground‐water management. The results of the analysis suggest that approaches taken to ground‐water management reform in Oklahoma, and the other eastern Ogallala states, may be more effective and realistic than might initially be thought.Oklahoma's present ground‐water law, adopted in 1973, is based on a utilization policy of planned depletion and represents a major change in direction entailing significant implementation costs. Agricultural interests, seeking to protect their irrigation rights, were influential in both the adoption and implementation processes. Considering the problems encountered, the immediate outlook for effective state management of ground water remains unfavorable. Future prospects, however, are more favorable. Oklahoma has developed an institutional structure capable of responding to changing priorities and needs of irrigators. This long‐run approach to ground‐water management matches the interests of the most relevant political constituency and may prove to be the most e

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1987.tb02883.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

ABSTRACTContaminants from uranium tailings disposed of at an active mill in Colorado have seeped into the shallow ground water onsite. This ground water discharges into the Arkansas River Valley through a superposed stream channel cut in the resistant sandstone ridge at the edge of a synclinal basin. In the river valley, seasonal surface‐water irrigation has a significant impact on hydrodynamics. Water levels in residential wells fluctuate up to 20 ft and concentrations of uranium, molybdenum, and other contaminants also vary seasonally, with highest concentrations in the Spring, prior to irrigation, and lowest concentrations in the Fall. Results of a simple transient mixing cell model support the hypothesis that lateral ground‐water inflow, and not irrigation recharge, is the source of ground‐water contamin

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1987.tb02884.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

ABSTRACTResults from the first phase of a study on water movement within the till of east‐central South Dakota indicate that little to no water passes from the weathered till through the underlying unweathered till into underlying outwash deposits. Based on hydrographic analyses, field hydraulic conductivity measurements, and major‐ion sampling at 22 study sites, discharge from the weathered till is hypothesized to be primarily from evapotranspirative losses during periods of high water table. Hydraulic conductivity of the unweathered till is typically 10 to 200 times lower than the weathered till. Water sampled from the unweathered till is up to three times higher in major‐ion concentrations than water in underlying outwash deposits. Carbon‐age dates of water from the buried outwash deposits suggest an age in excess of 9,000 years before the present, corresponding to the Late Wisconsinan glacia

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1987.tb02885.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

ABSTRACTStudies of moisture migration in the vadose zone were conducted at four field sites using a reverse Schlumberger resistivity array. Gravimetric moisture measurements on soil samples taken at each of the field sites were made to a maximum depth of 1.83 meters, and these results were correlated with resistivity values. Tensiometer measurements were also taken at two of the four sites. The soils at the sites have combined clay and silt content (less than .0625 mm grain size) which varies from 13% to 84%. Three of the sites are underlain by sand or gravel in the unsaturated zone. The fourth site has fractured but relatively impermeable shales and siltstones under the surface soils. Depths to water table varied from 1.58 m to 13.7 m. Resistivity and gravimetric moisture measurements were carried out prior to the addition of water to the surface, and following the application of water, either by watering of the site (at two sites) or during and after rainfall events (at two sites). Monitoring was carried out for periods of one to three weeks. Results indicate that (1) moisture is retained for long periods of time in clay/silt‐rich soils; (2) moisture migration is slow below a moist soil zone and is not readily detected by surface resistivity measurements; and (3) near‐surface moisture changes can be defined by surface resistiv

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1987.tb02886.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

ABSTRACTThe occurrence of low‐level hits of volatile organic priority pollutant compounds is statistically modeled as a Poisson process. Methods are developed to estimate the mean of the Poisson distribution for a random sample of volatile organic measurements as well as 99% prediction limits and 99% tolerance limits. The prediction limits provide an interval estimate that will include values obtained for the nextkfuture measurements based on a sample ofnprevious measurements with 99% confidence. The tolerance limits provide an interval estimate for thenprevious measurements that will contain 99% of the population of background measurements with 95% confidence. These methods are illustrated with measurements obtained from 61 field blanks, 56 trip blanks, and 162 samples obtained from 29 upgradient wells. Both prediction and tolerance limits yielded extremely similar results in all three example

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1987.tb02887.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

ABSTRACTBoreholes terminated with a short (1–3 m) length of screen are often used in ground‐water quality monitoring, although to obtain representative samples, pumping is often required to overcome the effects of stagnant casing storage. Methods for estimating pumping time prior to sampling from a pumped discharge, presented graphically and in summary equations, show that for most requirements, pumping time (ta) to purge well storage (where mixing of casing storage and ground water takes place within the casing) or to overcome casing storage effects (where little mixing occurs within the casing) is given byHere V is the volume of well storage, Q is the average pumping rate, and m is given bywhere Ct, Cg, and Ccare concentrations of some substance in pumpage, and ground water, and the initial concentration in casing storage, respectively. In boreholes which have been developed and which are regularly pumped and where a relative sampling error of 2.5% is considered to be acceptable, then m has a value of 0.1. Pumping time then equates to the time necessary to pump 2.3 volumes of well storage from the borehole.Laboratory and field evaluations using boreholes in transmissive and low permeability formations generally validate the theoretical approach. The theory can be used as a basis for estimating and optimizing pumping times for monitoring programs where ground‐water samples are recovered from short‐screened boreholes. Additionally, the theory allows the determination of an optimum pumpi

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1987.tb02888.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

ABSTRACTThis paper presents an analytical model for predicting contaminant transport from a Gaussian vertical strip source in a three‐dimensional uniform ground‐water flow field. The model takes account of hydrodynamic dispersion, adsorption, and decay. In addition, the effects of partial penetration of the contaminant source and finite aquifer thickness are accounted for. Dimensional analysis and type curve procedure are developed for evaluating steady‐state (or maximum attainable) concentration along the plume center line. Application of the type curve procedure is demonstrated. Also included in the presentation is a method for evaluating the effective decay constant of a nonconservative chemical, based on an assumption of simple hydrolysis. The proposed model has been compared with three other analytical models given in the literature. Two simulation examples are presented. Results of the comparison indicate certain advantages of the present model over its previous counter

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1987.tb02889.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY