Modelling the effects of climate change and its uncertainty on UK Chalk groundwater resources from an ensemble of global climate model projections

Laboratory experiments and numerical modeling have shown that dissolution in carbonate aquifers results in high-permeability channel networks. However, the lack of techniques to assess the extent and significance of these channel networks presents a major problem in characterizing carbonate aquifers. This problem was addressed by identifying the differences between two simulations (with and without channels) of the intensely studied limestone aquifer at Mammoth Cave (Kentucky, USA). Long-distance tracer-test results and spring discharges were used for assessing model accuracy as well as head measurements in wells. The channel simulation provided a much better calibration than the homogeneous porous-medium simulation and revealed five important differences: (1) convergent flow to large springs, (2) equipotentials forming troughs, (3) decreases in hydraulic gradient and (4) increases in hydraulic conductivity in a downgradient direction, and (5) substantial scaling effects. These five characteristics are also common in other carbonate aquifers and provide a means of identifying whether a carbonate aquifer is more similar to porous-medium or to karst-aquifer end members.

Diagnostic hydrogeologic characteristics of a karst aquifer (Kentucky, USA)

A salt water lens is found above fresh water under the shore between Dunkerque (France) and Nieuwpoort (Belgium). This inverse density distribution is in a dynamic equilibrium. It develops due to the infiltration of salt water on the back shore during high tide. Under this salt water lens, water infiltrated in the adjacent dune area flows towards the sea and discharges at the seabed. This water quality distribution differs from the classic salt water wedge under fresh water described in the literature. Here, the evolution to this water quality distribution is simulated with a density dependent numerical model. A large tidal range, shore morphology and a permeable groundwater reservoir are the main conditions for the observed water quality distribution. By altering these conditions, intermediate water quality distributions between the classic salt water wedge and the one discussed here develop. Based on these simulations, it is expected that similar kinds of inverse density distribution could be present in a number of coastal areas, which have tides, a gently sloping shore and a permeable substratum.

Occurrence of salt water above fresh water in dynamic equilibrium in a coastal groundwater flow system near De Panne, Belgium

Simulation and prediction of suprapermafrost groundwater level variation in response to climate change using a neural network model

Representation in regional models of saturated river–aquifer interaction for gaining/losing rivers

Preface1 IntroductionPART I: BASIC PRINCIPLES2 Background to Groundwater Flow3 Recharge due to Precipitation or Irrigation4 Interaction between Surface Water and GroundwaterPART II: RADIAL FLOW5 Radial Flow to Pumped Boreholes - Fundamental Issues6 Large Diameter Wells7 Radial Flow where Vertical Components of Flow are Significant8 Practical Issues of Interpretation and Assessing ResourcesPART III: REGIONAL GROUNDWATER FLOW9 Regional Groundwater Studies in which Transmissivity is Effectively Constant10 Regional Groundwater Flow in Multi-Aquifer Systems11 Regional Groundwater Flow with Hydraulic Conductivity Varying with Saturated Thickness12 Numerical Modelling InsightsAppendix: Computer Program for Two-zone ModelList of SymbolsReferencesIndex

K. R. Rushton

Papers

Groundwater Hydrology: Conceptual and Computational Models