Publications
152 results found
Mathias SA, Butler AP, Fowler G, et al., 2009, Beneficial hydraulic fracture propagation during in situ chemical oxidation, Contaminant Source Zone Characterisation and Remediation, Publisher: The Geological Society - Hydrogeological Group
Butler AP, Mathias SA, Gallagher AJ, et al., 2009, Analysis of flow processes in fractured chalk under pumped and ambient conditions, HYDROGEOL J, Vol: In Press, ISSN: 1431-2174
Ireson AM, Mathias SA, Wheater HS, et al., 2009, A model for flow in the Chalk unsaturated zone incorporating progressive weathering, J HYDROL, Vol: 365, Pages: 244-260, ISSN: 0022-1694
Mathias SA, Butler AP, 2008, Reply to comment by Robert P. Chapuis and Djaouida Chenaf on "Shape factors for constant-head double-packer permeameters'', WATER RESOURCES RESEARCH, Vol: 44, ISSN: 0043-1397
Jackson BM, Browne CA, Butler AP, et al., 2008, Nitrate transport in Chalk catchments: monitoring, modelling and policy implications, ENVIRONMENTAL SCIENCE & POLICY, Vol: 11, Pages: 125-135, ISSN: 1462-9011
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- Citations: 53
Mathias SA, Butler AP, Zhan H, 2008, Approximate solutions for Forchheimer flow to a well, J HYDRAUL ENG-ASCE, Vol: 134, Pages: 1318-1325, ISSN: 0733-9429
Mathias SA, Butler AP, Wheater HS, 2008, Modelling radioiodine transport across a capillary fringe, J ENV RAD, Vol: 99, Pages: 716-729, ISSN: 0265-931X
Wheater HS, Bell JNB, Butler AP, et al., 2007, Biosphere Implications of Deep Disposal of Nuclear Waste: The Upwards Migration of Radionuclides in Vegetated Soils, Publisher: Imperial College Press, ISBN: 978-1-86094-743-8
Mathias SA, Butler AP, Ireson AM, et al., 2007, Recent advances in modelling nitrate transport in the Chalk unsaturated zone, Q J ENG GEOL HYDROGEOL, Vol: 40, Pages: 353-359, ISSN: 1470-9236
Mathias SA, Butler AP, 2007, Flow to a finite diameter well in a horizontally anisotropic aquifer with well-bore storage, WATER RESOUR RES, Vol: 43, W07501, ISSN: 0043-1397
Jackson BM, Wheater HS, Wade AJ, et al., 2007, Catchment-scale modelling of flow and nutrient transport in the Chalk unsaturated zone, ECOL MODEL, Vol: 209, Pages: 41-52, ISSN: 0304-3800
Mathias SA, Butler AP, Peach DW, et al., 2007, Recovering tracer test input functions from fluid electrical conductivity logging in fractured porous rocks, ISSN: 0043-1397
Mathias SA, Butler AP, 2007, Shape factors for constant-head double-packer permeameters, WATER RESOUR RES, Vol: 43, W06430, ISSN: 0043-1397
Mathias SA, Butler AP, 2006, An improvement on Hvorslev's shape factors, GEOTECHNIQUE, Vol: 56, Pages: 705-706, ISSN: 0016-8505
Williams A, Bloomfield J, Griffiths K, et al., 2006, Characterising the vertical variations in hydraulic conductivity within the Chalk aquifer, JOURNAL OF HYDROLOGY, Vol: 330, Pages: 53-62, ISSN: 0022-1694
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- Citations: 41
Jackson BM, Wheater HS, Mathias SA, et al., 2006, A simple model of variable residence time flow and nutrient transport in the chalk, JOURNAL OF HYDROLOGY, Vol: 330, Pages: 221-234, ISSN: 0022-1694
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- Citations: 26
Ireson AM, Wheater HS, Butler AP, et al., 2006, Hydrological processes in the Chalk unsaturated zone - Insights from an intensive field monitoring programme, JOURNAL OF HYDROLOGY, Vol: 330, Pages: 29-43, ISSN: 0022-1694
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- Citations: 51
Mathias SA, Butler AP, Jackson BM, et al., 2006, Transient simulations of flow and transport in the Chalk unsaturated zone, JOURNAL OF HYDROLOGY, Vol: 330, Pages: 10-28, ISSN: 0022-1694
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- Citations: 51
Bakr MI, Butler AP, Guadagnini A, et al., 2006, State-space first-order estimate of well catchment uncertainty, IAHS-AISH Publication, Pages: 189-195, ISSN: 0144-7815
Nonstationarity of groundwater flow and transport processes is relevant in well capture zone design and wellhead protection. We introduce a State-Space First-Order approach as an alternative to numerical Monte Carlo methods to quantify the uncertainty associated with well catchment prediction. The mean and covariance of system state variables (i.e. head, pore water velocity and particle trajectory) are approximated by a first-order Taylor's series with sensitivity coefficients estimated from the adjoint operator for a system of discrete equations (state-space equations). By employing numerical solution methods, it is possible to handle irregular geometry, varying boundary conditions, complicated sink/source terms and different covariance functions, all of which are important factors for real-world applications. Results obtained using the State-Space First-Order method compare favourably with those from Monte Carlo analysis and are considerably more efficient.
Shields ARG, Butler AP, Daly P, et al., 2006, Monitoring of organic and inorganic parameters for a full-scale in situ pulsed air-sparging programme, LAND CONTAMINATION & RECLAMATION, Vol: 14, Pages: 329-334, ISSN: 0967-0513
Mathias SA, Butler AP, 2006, Linearized Richards' equation approach to pumping test analysis in compressible aquifers (Article no.W06408), Water Resources Research, Vol: 42, Pages: 1-10, ISSN: 0043-1397
[ 1] There is increasing acceptance of the importance of slow drainage from the unsaturated zone (SDUZ) when interpreting drawdown- time curves derived from pumping tests. Previous analytical solutions have generally assumed instantaneous drainage from the unsaturated zone. Such models typically underestimate the specific yield. Some authors have sought to account for SDUZ by assuming that drainage from the unsaturated zone declines exponentially with time, giving rise to an empirical delay index. These models tend to overestimate drawdown at early times and underestimate it during late times. More recently, the superposition of an arbitrary number of exponential models with different delay indices has been advocated, giving rise to an overparameterized and complicated empirical function. Following the work of Kroszynski and Dagan ( 1975), we obtain a new drainage function based on a linearized Richards' equation assuming that moisture content and hydraulic conductivity are exponential functions of pressure head. Furthermore, the drainage function can be incorporated into existing analytical solutions ( e. g., Moench, 1997) with minor adjustment. The resulting model requires an additional three parameters: a moisture retention exponent, a hydraulic conductivity exponent, and the initial unsaturated zone thickness. The new drainage function can also be used in an empirical fashion with only one parameter ( the other two are lost by assuming an infinitely deep unsaturated zone and that the moisture retention and relative permeability exponents are equal). Its applicability is demonstrated using pumping test data sets from Borden and Cape Cod. The results show improved consistency with the experimental data in comparison with previous studies.
Wheater HS, Bell JNB, Butler AP, et al., 2006, Biosphere Implications of Deep Disposal of Nuclear Waste: The Upwards Migration of Radionuclides in Vegetated Soils, London, Publisher: Imperial College Press, ISBN: 978-1-86094-743-8
Ireson AM, Wheater HS, Butler AP, et al., 2006, Movement of Water through the Chalk Unsaturated Zone: Development of a Depth-Dependent Model Parameterisation, Publisher: BOKU
van Leeuwen M, te Stroet CBM, Butler AP, et al., 2005, Stochastic determination of the Wierden (Netherlands) capture zones, GROUND WATER, Vol: 37, Pages: 8-17, ISSN: 0017-467X
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- Citations: 17
Mathias SA, Butler AP, McIntyre N, et al., 2005, The significance of flow in the matrix of the Chalk unsaturated zone, JOURNAL OF HYDROLOGY, Vol: 310, Pages: 62-77, ISSN: 0022-1694
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- Citations: 49
Stauffer F, Guadagnini A, Butler A, et al., 2005, Delineation of source protection zones using statistical methods, Water Resources Management, Vol: 19, Pages: 163-185, ISSN: 0920-4741
Source protection zones are increasingly important for securing the long-term viability of drinking water derived from groundwater resources. These may be either time-related capture zones or catchments related to the activity of a pumping well or spring. The establishment of such zones is an indispensable measure for the proper assessment of groundwater resource vulnerability and reduction of risk, which may be induced by human activities. The delineation of these protection zones is usually performed with the aid of models, which are in turn based on site-specific information of the aquifer's geometry, hydraulic parameters and boundary conditions. Owing to the imperfect knowledge of such information, predicting the location of these zones is inherently uncertain. It is possible to quantify this uncertainty in a statistical manner through the development of probability maps, which shows the probability that a particular surface location belongs to the aquifer's capture zone (or catchment area). This publication aims at the investigation of the requirements for the establishment of probabilistic source protection zones, the practical use of stochastic methods in their delineation, and the use of data-assimilation for uncertainty reduction. It also provides a methodology for the implementation of these methods by modelling practitioners. © Springer Science + Business Media, Inc. 2005.
Bakr MI, Butler AP, 2005, Nonstationary stochastic analysis in well capture zone design using first-order Taylor's series approximation, WATER RESOURCES RESEARCH, Vol: 41, ISSN: 0043-1397
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- Citations: 9
Bakr MI, Butler AP, 2004, Worth of head data in well-capture zone design: deterministic and stochastic analysis, JOURNAL OF HYDROLOGY, Vol: 290, Pages: 202-216, ISSN: 0022-1694
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- Citations: 10
Zacharof AI, Butler AP, 2004, Stochastic modelling of landfill leachate and biogas production incorporating waste heterogeneity. Model formulation and uncertainty analysis, WASTE MANAGEMENT, Vol: 24, Pages: 453-462, ISSN: 0956-053X
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- Citations: 40
Howden NJK, Wheater HS, Peach DW, et al., 2004, Hydrogeological controls on surface/groundwater interactions in a lowland permeable chalk catchment, London, Hydrology: science and practice for the 21st century, proceedings of the British Hydrological Society international conference, July 2004, Publisher: Imperial College London, Pages: 113-122
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