Groundwater Flow Properties Research Articles

Estimation of groundwater flow along complex coastal aquifers in presence of tidal waves

ABSTRACT Coastal aquifers are of interest for many years in understanding the transient interaction of tides and groundwater. With existing studies, water table fluctuations in the two zonal aquifers of various configurations separated by horizontal or sloping bases have been addressed; however, flow properties in respective aquifers are not addressed. The present study is an application of the previous study and it addresses flow properties such as flow rate at both ends of the complex coastal aquifer, and volumetric exchanges of groundwater at the proximity surface and at the boundary point. The combined effect of the bed slope and tidal waves on groundwater flow properties is addressed by obtaining the analytical expressions. Furthermore, numerical simulation using a finite difference method (FDM) is carried out for the flow rate and analytical solution is compared with it and found to be satisfactory. The hydrographs representing the flow rate and amount of groundwater exchanged are studied with different bed slopes and for various time lags. The flow analysis is carried out in a heterogeneous aquifer by changing various hydrological parameters. The study focused on dependency of groundwater hydraulic properties for the sloping zone on the horizontal zone. Based on the results, the groundwater flow in the complex aquifer systems is discussed.

Study of Groundwater Flow Properties in a Karst System by Coupled Analysis of Diverse Environmental Tracers and Discharge Dynamics

Monitoring of various naturally present substances or physical properties of the water, commonly called environmental tracers, can provide valuable insight in characteristics of groundwater flow systems and intrinsic processes. Analysis of individual tracer data most often gives an ambiguous interpretation, but employment of multiple diverse tracers can greatly increase interpretation reliability. We monitored multiple natural tracers including spring water electrical conductivity, temperature, loads of major anions and cations, stable isotopes of water, and total organic carbon together with discharge dynamics on Krbavica springs located in the Croatian part of Dinaric Karst region. We also monitored dissolved oxygen concentration as an indicator of “excess air” dynamics in the spring water, which is a very rarely recognized and not properly understood phenomenon in the karst groundwater studies. Analysis of the monitoring data revealed main characteristics of the karst system, among which following can be emphasized: (1) oxygen concentration together with conductivity and temperature (parameters monitored with high temporal resolution) were strongly related to discharge dynamics, while seasonal patterns were absent; (2) supersaturation with oxygen confirmed presence of “excess air”, most pronounced in high water conditions following the hydrograph peaks, indicating prevalence of closed flow conditions within the system; (3) electrical conductivity showed “anomalous” gradual decrease during the hydrograph recessions, attributed both to CO2 dynamics and mobilization of water from tiny fissures during high recharge conditions; and (4) stable isotope measurements confirmed good mixing of water within the system with mean residence time of a few years. Simultaneous monitoring of diverse tracer dynamics enabled detailed characterization of the karst system without excessive ambiguity.

Tracer test to assess flow and transport parameters of an earth slide: The Montecagno landslide case study (Italy)

Subsurface water processes are principle triggering and driving factors during slope movements. However, the hydraulic properties that drive groundwater flow along the slope remain poorly understood. Moreover, landslide deposits are often characterized by layering and fissures that cause high heterogeneity in the distribution of hydraulic properties. This heterogeneity leads to great uncertainty in the prediction of groundwater flow paths. This study aimed to improve understanding of hydraulic and transport properties of deep earth slides and to identify preferential flow directions inside the landslide body. A dye tracer test was used to estimate transport parameters and characterize groundwater flow paths. The results indicate that in the studied landslide, two groundwater flow types exist and are related to the presence of fissured rock blocks and debris horizons embedded in a fine matrix. The estimated low groundwater flow velocity has rarely been estimated in other studies of this landslide type. The groundwater flow direction appears to be mainly influenced by the failure surface shape and differs from the sliding direction. Our results differ from those in other landslide studies and improve our knowledge of groundwater flow properties in deep earth slides; furthermore, they offer a new contribution to slope stability analyses and formula, and to the effective design of mitigation strategies.

Contribution of water geochemistry and isotopes (δ18O, δ2H, 3H, 87Sr/86Sr and δ11B) to the study of groundwater flow properties and underlying bedrock structures of a deep landslide

A comprehensive understanding of bedrock lithology and groundwater circulation is necessary to identify areas prone to landslide initiation and reactivation. This necessity is particularly required in the case of outcroppings of weak rocks such as gypsum that, due to their high solubility and low mechanical strength, can promote slope deformation with the development of caves and collapses. In the Upper Secchia River Valley, where gypsum outcrops extensively and is covered by landslide deposits, an accurate identification of the gypsum outcrops and their distribution is needed to reduce the damage to urbanized slopes. In this paper, a hydrologic and geochemical approach is used in the Montecagno landslide to identify the origin, flow paths and transit time of groundwater circulating inside the landslide body and to identify gypsum deposits and their distribution in the bedrock. The results of groundwater-level monitoring, δ18O-δ2H and 3H isotope analyses and FLOWPC modelling suggest a local and recent origin of the groundwater hosted in shallow flow paths inside the landslide. Chemical and isotope (87Sr/86Sr, δ11B) analyses offer evidence of the presence inside the landslide of small blocks of gypsum that, due to their dimensions, probably have a minor influence on landslide stability. This research demonstrates that the methodology used can provide satisfactory information about bedrock structures and their hydrological aspects.

Quantitative Estimates of Non-Darcy Groundwater Flow Properties and Normalized Hydraulic Aperture through Discrete Open Rough-Walled Joints

Quantitative Estimates of Non-Darcy Groundwater Flow Properties and Normalized Hydraulic Aperture through Discrete Open Rough-Walled Joints

Tide-Induced Groundwater Flow Properties Along Sloping Unconfined Coastal Aquifer

Tidal attenuation on groundwater flow properties is a crucial aspect in understanding groundwater-surface water interaction along coastal beaches. In this article, an analytical model is developed for describing the flow in the sloping unconfined aquifer bounded by ocean water along one side. Closed form of the transient solution from the linearized Boussinesq equation is obtained with exponentially decreasing tidal boundary condition. Numerical solution of nonlinear hydrodynamic equation is derived to assess the validity of linearization method. In this regard, the Alternate Direction Implicit (ADI) Method is applied, which is further used to obtain the impact of recharge on groundwater flow from non-linear Advection-Convection equation. Sensitivity analysis for larger amplitudes over smaller mean depths of saturation is carried out to obtain the validity of linearization technique. For varying bed slopes, water table fluctuation is analyzed using various tidal components. The error statistics involving mean error and Relative Percentage Difference (RPD) show that both solutions are in good agreement with each other. The flow rate and volumetric exchange are discussed to elaborate the flow analysis of groundwater in the interaction. The bed slope is considered along the inland side and the results are discussed briefly with graphs. Similarly, the flow behavior along the coastal side is presented in tabular values.

Hydrogeophysical investigation of groundwater potential and aquifer vulnerability prediction in basement complex terrain – A case study from Akure, Southwestern Nigeria

Abstract This study provides a model for the prediction of groundwater potential and vulnerability of basement aquifers in parts of Akure, Southwestern Nigeria. Hydrogeophysical surveys involving very-low-frequency electromagnetic (VLF-EM) profiling and electrical resistivity (ER) sounding, as well as evaluation of hydraulic gradient using three-point method, were carried out. Ten VLF-EM reconnaissance survey traverses, with lengths ranging from 55 m to 75 m, at 10 m station separation, and 12 vertical electrical sounding (VES) stations were occupied. Two-dimensional map of the filtered real component reveals areas of high conductivity, indicative of linear features that can serve as a reservoir or conduit for fluid flow. Interpretation of the VES results delineates three to four geoelectric units. Two aquifer zones were identified, with resistivity values in the ranges of 20 Ωm to 310 Ωm and 100 Ωm to 3,000 Ω m, respectively. Transverse resistance, longitudinal conductance, coefficient of anisotropy and hydraulic gradient have values ranging from 318.2 Ωm2 to 1,041.8 Ωm2, 0.11 mhos to 0.39 mhos, 1.04 to 1.74 and 0.017 to 0.05, respectively. The results of this study identified two prospective borehole locations and the optimum position to site the proposed septic system, based on the aquifer’s protective capacity and groundwater flow properties.

ICONE19-43163 DEVELOPMENT OF A METHODOLOGY FOR THE CHARACTERISATION OF LONG-TERM GEOSPHERE EVOLUTION : (1) IMPACTS OF NATURAL EVENTS AND PROCESSES ON THE GEOSPHERE EVOLUTION OF COASTAL SETTING, IN THE CASE OF HORONOBE AREA

A critical issue for building confidence in the long-term safety of geological disposal is to demonstrate the stability of the geosphere, taking into account its likely future evolution. This stability is broadly defined as the persistence of Thermal-Hydrological-Mechanical-Chemical conditions considered favourable for the long-term safety of a geological repository. This study provides the conceptualisation and preliminary results of numerical simulations of the long-term geosphere evolution, especially groundwater flow properties, in the Horonobe area, Hokkaido, northern Japan, based on data from the JAEA's underground research laboratory project. Information on natural events and processes has been integrated into a chronological conceptual model, which indicates space-time sequences of the events and processes in the Horonobe area over geological time. Spatial scale for the numerical simulations are based on the recharge and discharge area in the present and the past glacial periods, and the direction of the groundwater flow in the present of Horonobe area. Time scale for the numerical simulations over the last 1.5 million years are defined by the palaeogeography of Horonobe area, and mainly focused on the changes of the geological structure (i.e. hydrogeological structure), recharge rate, and distribution of sea and land area caused by sub-surface and earth-surface processes such as crustal movement, climatic and sea-level changes. The results of the simulation show that the range and magnitude of change in groundwater flow properties, and sensitivity of the properties to the sea-level and elevation changes due to crustal movement have close relationship with the distribution and the evolution of the hydraulic conductivities of geological formations.

Influence of morphology and permafrost dynamics on hyporheic exchange in arctic headwater streams under warming climate conditions

We investigated surface‐subsurface (hyporheic) exchange in two morphologically distinct arctic headwater streams experiencing warming (thawing) sub‐channel conditions. Empirically parameterized and calibrated groundwater flow models were used to assess the influence of sub‐channel thaw on hyporheic exchange. Average thaw depths were at least two‐fold greater under the higher‐energy, alluvial stream than under the low‐energy, peat‐lined stream. Alluvial hyporheic exchange had shorter residence times and longer flowpaths that occurred across greater portions of the thawed sediments. For both reaches, the morphologic (longitudinal bed topography) and hydraulic conditions (surface and groundwater flow properties) set the potential for hyporheic flow. Simulations of deeper thaw, as predicted under a warming arctic climate, only influence hyporheic exchange until a threshold depth. This depth is primarily determined by the hydraulic head gradients imposed by the stream morphology. Therefore, arctic hyporheic exchange extent is likely to be independent of greater sub‐stream thaw depths.

Applied hydrogeology for scientists and engineers

Introduction Hydrogeology of Groundwater Reservoirs Groundwater Flow Properties Aquifer Properties Groundwater Flow Laws Water Wells Field Measurements Steady-State Flow Aquifer Tests Porous Medium Aquifer Tests Fractured Medium Aquifer Tests Well Test Nonlinear Flow Aquifer Tests Index