scholarly journals Environmental hydrochemical and stabile isotope methods used to characterise the relation between karst water and surface water

2017 ◽  
Vol 6 (1) ◽  
Author(s):  
Romeo Eftimi ◽  
Tete Akiti ◽  
Sokrat Amataj ◽  
Ralf Benishke ◽  
Hans Zojer ◽  
...  
Keyword(s):  
Groundwater Flow ◽  
Large Scale ◽  
Total Hardness ◽  
Karst Water ◽  
Karst Aquifers ◽  
Water Conductivity ◽  
Altitude Effect ◽  
Classical Study ◽  
Recharge Sources ◽  
Stabile Isotope

Karst aquifers are characterized by high heterogeneity of groundwater flow. The classical study methods such as boreholes, pumping tests, and point observations give important data but cannot be extended to the entire aquifer. However the environmental hydrochemical and stabile isotope methods could give important information about large scale aquifer characterization. Some study examples from Albania, shown in this paper, demonstrate the successful application of the isotope methods, which are more powerful if applied in combination with hydrochemical ones, for the identification of the karst water recharge sources. Among the isotope methods the altitude effect seems to be more indicative for the solution of the problem concerned. For characterising the lithology of karst rocks and the physical aspects of karst aquifers (type of groundwater flow) the combined use of some hydrochemical parameters like the water conductivity, total hardness, ionic ratios rCa/ rMg, rSO4/r/mg, CO2 pressure and the indexes of calcite and (Sic) and of dolomite saturation (Sid), result very useful.

scholarly journals Representation of water abstraction from a karst conduit with numerical discrete-continuum models

2014 ◽  
Vol 18 (1) ◽  
pp. 227-241 ◽  
Author(s):  
T. Reimann ◽  
M. Giese ◽  
T. Geyer ◽  
R. Liedl ◽  
J. C. Maréchal ◽  
...  
Keyword(s):  
Boundary Condition ◽  
Large Scale ◽  
Pumping Test ◽  
Karst Water ◽  
Karst Aquifers ◽  
Flow Process ◽  
Conduit Flow ◽  
Water Abstraction ◽  
Model Studies ◽  
Karst Conduit

Abstract. Karst aquifers are characterized by highly conductive conduit flow paths embedded in a less conductive fissured and fractured matrix, resulting in strong permeability contrasts with structured heterogeneity and anisotropy. Groundwater storage occurs predominantly in the fissured matrix. Hence, most mathematical karst models assume quasi-steady-state flow in conduits neglecting conduit-associated drainable storage (CADS). The concept of CADS considers storage volumes, where karst water is not part of the active flow system but hydraulically connected to conduits (for example karstic voids and large fractures). The disregard of conduit storage can be inappropriate when direct water abstraction from karst conduits occurs, e.g., large-scale pumping. In such cases, CADS may be relevant. Furthermore, the typical fixed-head boundary condition at the karst outlet can be inadequate for water abstraction scenarios because unhampered water inflow is possible. The objective of this work is to analyze the significance of CADS and flow-limited boundary conditions on the hydraulic behavior of karst aquifers in water abstraction scenarios. To this end, the numerical discrete-continuum model MODFLOW-2005 Conduit Flow Process Mode 1 (CFPM1) is enhanced to account for CADS. Additionally, a fixed-head limited-flow (FHLQ) boundary condition is added that limits inflow from constant head boundaries to a user-defined threshold. The effects and the proper functioning of these modifications are demonstrated by simplified model studies. Both enhancements, CADS and FHLQ boundary, are shown to be useful for water abstraction scenarios within karst aquifers. An idealized representation of a large-scale pumping test in a karst conduit is used to demonstrate that the enhanced CFPM1 is able to adequately represent water abstraction processes in both the conduits and the matrix of real karst systems, as illustrated by its application to the Cent Fonts karst system.

scholarly journals Representation of water abstraction from a karst conduit with numerical discrete-continuum models

2013 ◽  
Vol 10 (4) ◽  
pp. 4463-4487
Author(s):  
T. Reimann ◽  
M. Giese ◽  
T. Geyer ◽  
R. Liedl ◽  
J. C. Maréchal ◽  
...  
Keyword(s):  
Boundary Condition ◽  
Large Scale ◽  
Pumping Test ◽  
Karst Water ◽  
Karst Aquifers ◽  
Flow Process ◽  
Conduit Flow ◽  
Water Abstraction ◽  
Model Studies ◽  
Karst Conduit

Abstract. Karst aquifers are characterized by highly conductive conduit flow paths embedded in a less conductive fissured and fractured matrix resulting in strong permeability contrasts with structured heterogeneity and anisotropy. Groundwater storage occurs predominantly in the fissured matrix. Hence, most karst models assume quasi steady-state flow in conduits neglecting conduit associated drainable storage (CADS). The concept of CADS considers storage volumes, where karst water is not part of the active flow system but rather hydraulically connected to conduits (for example karstic voids and large fractures). The disregard of conduit storage can be inappropriate when direct water abstraction from karst conduits occurs, e.g. large scale pumping. In such cases, CADS may be relevant. Furthermore, the typical fixed head boundary condition at the karst outlet can be inadequate for water abstraction scenarios because unhampered water inflow is possible. The objective of this paper is to analyze the significance of CADS and flow-limited boundary conditions on the hydraulic behavior of karst aquifers in water abstraction scenarios. To this end, the numerical hybrid model MODFLOW-2005 Conduit Flow Process Mode 1 (CFPM1) is enhanced to account for CADS. Additionally, a fixed-head limited-flow (FHLQ) boundary condition is added that limits inflow from constant head boundaries to a user-defined threshold. The affect and proper functioning of these modifications is demonstrated by simplified model studies. Both enhancements, CAD storage and the FHLQ boundary, are shown to be useful for water abstraction scenarios within karst aquifers. An idealized representation of a large-scale pumping test in a karst conduit is used to demonstrate that the enhanced CFPM1 is potentially able to adequately represent water abstraction processes in both the conduits and the matrix of real karst systems.

scholarly journals Process-based karst modelling to relate hydrodynamic and hydrochemical characteristics to system properties

2013 ◽  
Vol 17 (8) ◽  
pp. 3305-3321 ◽  
Author(s):  
A. Hartmann ◽  
M. Weiler ◽  
T. Wagener ◽  
J. Lange ◽  
M. Kralik ◽  
...  
Keyword(s):  
Sensitivity Analysis ◽  
Groundwater Flow ◽  
Large Scale ◽  
Model Parameters ◽  
Karst Water ◽  
Flow Duration ◽  
Flow Duration Curves ◽  
System Properties ◽  
Karst Systems ◽  
Sensitive Parameters

Abstract. More than 30% of Europe's land surface is made up of karst exposures. In some countries, water from karst aquifers constitutes almost half of the drinking water supply. Hydrological simulation models can predict the large-scale impact of future environmental change on hydrological variables. However, the information needed to obtain model parameters is not available everywhere and regionalisation methods have to be applied. The responsive behaviour of hydrological systems can be quantified by individual metrics, so-called system signatures. This study explores their value for distinguishing the dominant processes and properties of five different karst systems in Europe and the Middle East. By defining ten system signatures derived from hydrodynamic and hydrochemical observations, a process-based karst model is applied to the five karst systems. In a stepwise model evaluation strategy, optimum parameters and their sensitivity are identified using automatic calibration and global variance-based sensitivity analysis. System signatures and sensitive parameters serve as proxies for dominant processes, and optimised parameters are used to determine system properties. By sensitivity analysis, the set of system signatures was able to distinguish the karst systems from one another by providing separate information about dominant soil, epikarst, and fast and slow groundwater flow processes. Comparing sensitive parameters to the system signatures revealed that annual discharge can serve as a proxy for the recharge area, that the slopes of the high flow parts of the flow duration curves correlate with the fast flow storage constant, and that the dampening of the isotopic signal of the rain as well as the medium flow parts of the flow duration curves have a non-linear relation to the distribution of groundwater storage constants that represent the variability of groundwater flow dynamics. Our approach enabled us to identify dominant processes of the different systems and provided directions for future large-scale simulation of karst areas to predict the impact of future change on karst water resources.

Groundwater age from multi-level bores: What it can tell about the aquifers

2021 ◽  
Author(s):  
Uwe Morgenstern ◽  
Zara Rawlinson
Keyword(s):  
Groundwater Flow ◽  
Groundwater Recharge ◽  
Sea Level ◽  
Preferential Flow ◽  
Groundwater Age ◽  
Geological Processes ◽  
Recharge Sources ◽  
Transient Electromagnetic ◽  
Geophysical Surveys ◽  
Multi Level

<p>Geologic data to provide information on the functioning of aquifers is often scars. For the aquifers underlying the Heretaunga Plains, Hawkes Bay, one of New Zealand’s most important groundwater systems, we used groundwater age (tritium, SF6, 14C) to inform the geologic model and to provide information on groundwater flow through alternating strata of permeable river gravel beds and fine impermeable beds that form an interconnected unconfined–confined aquifer system with complex groundwater flow processes.</p><p>The aquifers are a result of geological processes responding to climate change cycles from cold glacial when sea level was more than 100m below present sea level, to warm interglacial periods with sea level similar to present day. Glacial climate strata are river gravel, sand and silt deposits and include the artesian aquifers. The interglacial strata form the aquicludes and are marine sand, silt, and clay deposits with interbedded estuarine, swamp and coastal fluvial silt, clay, peat and gravel deposits.</p><p>We have re-visited tracer data sampled during the drilling of multi-level observation well in the early 1990s, and collected new samples from these multi-level bores in order to understand in 3D the groundwater recharge sources, groundwater recharge and flow rates, connection to the rivers, and potential groundwater discharge out to sea. Consistently young water (c. 25 years) at depth greater than 100m indicates preferential flow paths, likely related to paleo-river channels. The flow pattern obtained from the water tracer data improves the geologic information from the drill-holes, and fits with information from recent airborne transient electromagnetic (SkyTEM) geophysical surveys.</p>

scholarly journals Improved representation of groundwater at a regional scale – coupling of mesocale Hydrologic Model (mHM) with OpeneGeoSys (OGS)

2017 ◽  
Author(s):  
Miao Jing ◽  
Falk Heße ◽  
Wenqing Wang ◽  
Thomas Fischer ◽  
Marc Walther ◽  
...  
Keyword(s):  
Time Series ◽  
Groundwater Flow ◽  
Groundwater Recharge ◽  
Large Scale ◽  
Groundwater Modeling ◽  
Coupled Model ◽  
Hydrologic Model ◽  
Source Modeling ◽  
Prediction Ability ◽  
Groundwater Head

Abstract. Most of the current large scale hydrological models do not contain a physically-based groundwater flow component. The main difficulties in large-scale groundwater modeling include the efficient representation of unsaturated zone flow, the characterization of dynamic groundwater-surface water interaction and the numerical stability while preserving complex physical processes and high resolution. To address these problems, we propose a highly-scalable coupled hydrologic and groundwater model (mHM#OGS) based on the integration of two open-source modeling codes: the mesoscale hydrologic Model (mHM) and the finite element simulator OpenGeoSys (OGS). mHM#OGS is coupled using a boundary condition-based coupling scheme that dynamically links the surface and subsurface parts. Nested time stepping allows smaller time steps for typically faster surface runoff routing in mHM and larger time steps for slower subsurface flow in OGS. mHM#OGS features the coupling interface which can transfer the groundwater recharge and river baseflow rate between mHM and OpenGeoSys. Verification of the coupled model was conducted using the time-series of observed streamflow and groundwater levels. Moreover, we force the transient model using groundwater recharge in two scenarios: (1) spatially variable recharge based on the mHM simulations, and (2) spatially homogeneous groundwater recharge. The modeling result in first scenario has a slightly higher correlation with groundwater head time-series, which further validates the plausibility of spatial groundwater recharge distribution calculated by mHM in the mesocale. The statistical analysis of model predictions shows a promising prediction ability of the model. The offline coupling method implemented here can reproduce reasonable groundwater head time series while keep a desired level of detail in the subsurface model structure with little surplus in computational cost. Our exemplary calculations show that the coupled model mHM#OGS can be a valuable tool to assess the effects of variability in land surface heterogeneity, meteorological, topographical forces and geological zonation on the groundwater flow dynamics.

CUDA-based solver for large-scale groundwater flow simulation

2011 ◽  
Vol 28 (1) ◽  
pp. 13-19 ◽  
Author(s):  
Xiaohui Ji ◽  
Tangpei Cheng ◽  
Qun Wang
Keyword(s):  
Groundwater Flow ◽  
Large Scale ◽  
Flow Simulation

Multiscale-finite-element-based ensemble Kalman filter for large-scale groundwater flow

2012 ◽  
Vol 468-469 ◽  
pp. 22-34 ◽  
Author(s):  
Liangsheng Shi ◽  
Lingzao Zeng ◽  
Dongxiao Zhang ◽  
Jinzhong Yang
Keyword(s):  
Finite Element ◽  
Kalman Filter ◽  
Groundwater Flow ◽  
Ensemble Kalman Filter ◽  
Large Scale ◽  
Multiscale Finite Element
Sign in / Sign up

Export Citation Format

Share Document