- Email: [email protected]
A groundwater trace study using a fluorescent dye
HYDROGEOLOGY:FLUID FLOW
247A
major importance for karst groundwater flow are confirmed by numerous field investigations. (from Author)
for three potential flow problems of HYDROCOIN Level 1. (from Author)
966049 Application of uncertainty analysis to groundwater pollution modelling A. G. Bobba, V. P. Singh & L. Bengtsson, Environmental Geology, 26(2), 1995, pp 89-96. Prediction and evaluation of pollution of the subsurface environment and planning remedial actions at existing sites may be useful for siting and designing new land-based waste treatment or disposal facilities. Most models used to make such predictions assume that the system behaves deterministically. A variety of factors, however, introduce uncertainty into the model predictions. The factors include model and pollution transport parameters and geometric uncertainty. The Monte Carlo technique is applied to evaluate the uncertainty, as illustrated by applying three analytical groundwater pollution transport models. The uncertainty analysis provides estimates of statistical reliability in model outputs of pollution concentration and arrival time. (from Authors)
966053 Three-dimensional groundwater flow near narrow surface water bodies L. C. Meigs & J. M. Bahr, Water Resources Research, 31(12), 1995, pp 3299-3307. A series of natural gradient tracer tests was conducted to delineate groundwater flow patterns near a drainage ditch in glacial outwash of central Wisconsin. Water level and precipitation data were collected to document factors that could contribute to temporal variations in the flow field. Year-to-year variations in recharge generated shifts in flow paths between replicate tracer experiments. The field data provided the basis for numerical modeling designed to elucidate the sensitivity of flow paths to variations in recharge. A three-dimensional aspect of flow paths identified in this study is a 'wrap-around' pattern, in which groundwater passes under a surface water body prior to turning in the downstream direction and continuing to migrate as subsurface flow. (from Authors)
966050 An analysis of perturbation based methods for the treatment of parameter uncertainty in numerical groundwater models L. D. Connell, Transport in Porous Media, 21(3), 1995, pp 225-240. Taylor series based procedures offer an alternative to Monte Carlo methods for calculating prediction statistics. Two such approaches, the first-order second moment and McLaughlin and Wood's perturbation method, are based on using a Taylor series to derive approximate expressions for the model predictions first and second statistical moments. In this paper the perturbation method presented by McLaughlin and Wood is rederived using Vetter matrix notation. This is compared with the first-order second moment (FOSM) method. The steady state expressions are shown to be equivalent, the transient forms considerably different. A new form of the FOSM is derived, which is simpler and has a lower computational burden. However, the transient McLanghlin and Wood expression is found to have a significantly lower computational overhead than either of the FOSM methods presented. (from Author) 966051 Continuous transmissivity transitions for horizontal groundwater flow models B. Odenwald, J. Stamm & B. Herrling, Advances in Water Resources, 18(5), 1995, pp 257-265. In the southern part of Germany, shallow and mostly unconfined valley aquifers are widespread. The differential equation describing groundwater flow and its boundary conditions varies for different flow situations due to the transient nature of the groundwater table. This paper present a continuous physical-mathematical formulation of twodimensional horizontal groundwater flow, which allows for a simultaneous computation of saturated unconfined, partially unsaturated, or confined aquifers. (from Authors) 966052 Mixed finite elements for accurate particle tracking in saturated groundwater flow E. F. Kaasschieter, Advances in Water Resources, 18(5), 1995, pp 277-294. Saturated groundwater flow can often be described by the law of mass conservation and Darcy's law, i.e. by a potential flow problem. An accurate approximation of the specific discharge can be determined by the mixed finite element method. In this article the lowest-order mixed method is presented including its hybridization, which results in a sparse symmetric positive definite system of linear equations. The applicability and advantages of the mixed finite element method are illustrated
966054 Prediction of groundwater flow J. Zhao, in: Engineering geology of waste disposal, ed S.P. Bentley, (Geological Society of London; Engineering Geology Special Publication, 11), 1996, pp 231-236. Predictions using an improved hydraulic model show that the permeability of a rock mass decreases with increasing depth; the groundwater flow into and around the repository, however, increases with repository depth until it reaches a maximum rate. The groundwater flow stabilizes or decreases after the peak rate due to joint closure of the rock mass surrounding the repository under high in situ stress. (from Author) 966055 A groundwater trace study using a fluorescent dye M. Townend & R. Aldridge, in: Engineering geology of waste disposal, ed S.P. Bentley, (Geological Society of London; Engineering Geology Special Publication, 11), 1996, pp 145147. The test procedure for a groundwater trace study in a sandstone aquifer is described. The field test was simple, quickly implemented and carried out within a limited budget. A result was obtained and this formed part of the hydrogeological assessment of the site. (Authors) 966056 Field-based determination of air diffusivity using soil air and atmospheric pressure time series S. Rojstaczer & J. P. Tunks, Water Resources Research, 31(12), 1995, pp 3337-3343. Air diffusivity in two zones over a 4.6-m interval of the unsaturated zone was determined through analysis of atmospheric pressure and soil air pressure time series. Regression analysis was used to calculate the ratio of amplitudes (admittance) and phase lag between these series at diurnal and semidiurnal frequencies. The admittance for each of the monitoring zones was close to unity for both frequencies. Phase lags between the two time series were statistically equivalent to zero at the diurnal frequency but were as large as 20 ° _+ 7° at the semidiurnal frequency. The absence of large variability in air diffusivity and the trends in phase shift with depth suggest that macropores or fractures propagate through a clay layer at a depth of 0.5-1.2 m. (from Authors) 966057 Research into the mobility of a gas phase within a porous network U. Boltze & M. H. De Freitas, in: Engineering geology of waste disposal, ed S.P. Bentley, (Geological Society of London; Engineering Geology Special Publication, 11), 1996, pp 313-322.
247A
major importance for karst groundwater flow are confirmed by numerous field investigations. (from Author)
for three potential flow problems of HYDROCOIN Level 1. (from Author)
966049 Application of uncertainty analysis to groundwater pollution modelling A. G. Bobba, V. P. Singh & L. Bengtsson, Environmental Geology, 26(2), 1995, pp 89-96. Prediction and evaluation of pollution of the subsurface environment and planning remedial actions at existing sites may be useful for siting and designing new land-based waste treatment or disposal facilities. Most models used to make such predictions assume that the system behaves deterministically. A variety of factors, however, introduce uncertainty into the model predictions. The factors include model and pollution transport parameters and geometric uncertainty. The Monte Carlo technique is applied to evaluate the uncertainty, as illustrated by applying three analytical groundwater pollution transport models. The uncertainty analysis provides estimates of statistical reliability in model outputs of pollution concentration and arrival time. (from Authors)
966053 Three-dimensional groundwater flow near narrow surface water bodies L. C. Meigs & J. M. Bahr, Water Resources Research, 31(12), 1995, pp 3299-3307. A series of natural gradient tracer tests was conducted to delineate groundwater flow patterns near a drainage ditch in glacial outwash of central Wisconsin. Water level and precipitation data were collected to document factors that could contribute to temporal variations in the flow field. Year-to-year variations in recharge generated shifts in flow paths between replicate tracer experiments. The field data provided the basis for numerical modeling designed to elucidate the sensitivity of flow paths to variations in recharge. A three-dimensional aspect of flow paths identified in this study is a 'wrap-around' pattern, in which groundwater passes under a surface water body prior to turning in the downstream direction and continuing to migrate as subsurface flow. (from Authors)
966050 An analysis of perturbation based methods for the treatment of parameter uncertainty in numerical groundwater models L. D. Connell, Transport in Porous Media, 21(3), 1995, pp 225-240. Taylor series based procedures offer an alternative to Monte Carlo methods for calculating prediction statistics. Two such approaches, the first-order second moment and McLaughlin and Wood's perturbation method, are based on using a Taylor series to derive approximate expressions for the model predictions first and second statistical moments. In this paper the perturbation method presented by McLaughlin and Wood is rederived using Vetter matrix notation. This is compared with the first-order second moment (FOSM) method. The steady state expressions are shown to be equivalent, the transient forms considerably different. A new form of the FOSM is derived, which is simpler and has a lower computational burden. However, the transient McLanghlin and Wood expression is found to have a significantly lower computational overhead than either of the FOSM methods presented. (from Author) 966051 Continuous transmissivity transitions for horizontal groundwater flow models B. Odenwald, J. Stamm & B. Herrling, Advances in Water Resources, 18(5), 1995, pp 257-265. In the southern part of Germany, shallow and mostly unconfined valley aquifers are widespread. The differential equation describing groundwater flow and its boundary conditions varies for different flow situations due to the transient nature of the groundwater table. This paper present a continuous physical-mathematical formulation of twodimensional horizontal groundwater flow, which allows for a simultaneous computation of saturated unconfined, partially unsaturated, or confined aquifers. (from Authors) 966052 Mixed finite elements for accurate particle tracking in saturated groundwater flow E. F. Kaasschieter, Advances in Water Resources, 18(5), 1995, pp 277-294. Saturated groundwater flow can often be described by the law of mass conservation and Darcy's law, i.e. by a potential flow problem. An accurate approximation of the specific discharge can be determined by the mixed finite element method. In this article the lowest-order mixed method is presented including its hybridization, which results in a sparse symmetric positive definite system of linear equations. The applicability and advantages of the mixed finite element method are illustrated
966054 Prediction of groundwater flow J. Zhao, in: Engineering geology of waste disposal, ed S.P. Bentley, (Geological Society of London; Engineering Geology Special Publication, 11), 1996, pp 231-236. Predictions using an improved hydraulic model show that the permeability of a rock mass decreases with increasing depth; the groundwater flow into and around the repository, however, increases with repository depth until it reaches a maximum rate. The groundwater flow stabilizes or decreases after the peak rate due to joint closure of the rock mass surrounding the repository under high in situ stress. (from Author) 966055 A groundwater trace study using a fluorescent dye M. Townend & R. Aldridge, in: Engineering geology of waste disposal, ed S.P. Bentley, (Geological Society of London; Engineering Geology Special Publication, 11), 1996, pp 145147. The test procedure for a groundwater trace study in a sandstone aquifer is described. The field test was simple, quickly implemented and carried out within a limited budget. A result was obtained and this formed part of the hydrogeological assessment of the site. (Authors) 966056 Field-based determination of air diffusivity using soil air and atmospheric pressure time series S. Rojstaczer & J. P. Tunks, Water Resources Research, 31(12), 1995, pp 3337-3343. Air diffusivity in two zones over a 4.6-m interval of the unsaturated zone was determined through analysis of atmospheric pressure and soil air pressure time series. Regression analysis was used to calculate the ratio of amplitudes (admittance) and phase lag between these series at diurnal and semidiurnal frequencies. The admittance for each of the monitoring zones was close to unity for both frequencies. Phase lags between the two time series were statistically equivalent to zero at the diurnal frequency but were as large as 20 ° _+ 7° at the semidiurnal frequency. The absence of large variability in air diffusivity and the trends in phase shift with depth suggest that macropores or fractures propagate through a clay layer at a depth of 0.5-1.2 m. (from Authors) 966057 Research into the mobility of a gas phase within a porous network U. Boltze & M. H. De Freitas, in: Engineering geology of waste disposal, ed S.P. Bentley, (Geological Society of London; Engineering Geology Special Publication, 11), 1996, pp 313-322.