Constraining permeabilities in a large-scale groundwater system through model calibration

Ophori, Duke

doi:10.1016/s0022-1694(99)00083-9

Cited by 22 publications

(17 citation statements)

References 45 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Furthermore, the variable density models (Figures 5 and 6) indicate that it is possible for saline water to occur close to the ground surface in discharge areas where groundwater movement is generally upward, and freshwater to recharge to great depths in recharge areas where movement is downward. This statement is in agreement with findings from modelling studies by Tóth and Sheng (1996), Ophori (1999) and Sheng and Tóth (2000), and is corroborated by field data from Fritz and Reardon (1979), Gascoyne et al (1987) and Davisson and Criss (1993).…”

Section: Generalsupporting

confidence: 90%

A simulation of large‐scale groundwater flow and travel time in a fractured rock environment for waste disposal purposes

Ophori

2004

Hydrological Processes

View full text Add to dashboard Cite

Abstract:Two-dimensional regional groundwater flow was simulated based on a conceptual model of low-permeability crystalline rocks of the Whiteshell Research Area (WRA) in south-eastern Manitoba. The conceptual model consists of fracture zones that strike in different directions and dip at various angles in the background rock mass. The thickness and hydraulic properties of the fracture zones in the conceptual model were varied as were the fluid properties and the boundary conditions of the groundwater flow system. The effects of these variations on the groundwater flow pattern and on the convective travel time along pathways from a hypothetical disposal vault at 500 m depth to discharge locations at the ground surface were evaluated. The vault was located in the regional discharge area of the groundwater system. A homogeneous conceptual model of the WRA, having only freshwater flow, formed a groundwater flow pattern with a regional flow system. Local flow systems developed increasingly with the introduction of fracture zones 20 m and 3 m thick, and depth-dependent fluid density. This indicates a reduction in groundwater residence time by fracture zones and fluid density. Flow pathways were analysed using both a stream-function and a particle-tracking technique. The pathways and their lengths from the location of the vault to the surface varied spatially according to the flow patterns. The minimum travel time along these pathways was less than 150 000 and greater than 4 000 000 years in models with and without fracture zones, respectively, indicating that the presence of fracture zones was the major controlling factor. A precise knowledge and refinement of conceptual model parameters is necessary during site selection for waste disposal purposes.

show abstract

Section: Generalsupporting

confidence: 90%

A simulation of large‐scale groundwater flow and travel time in a fractured rock environment for waste disposal purposes

Ophori

2004

Hydrological Processes

View full text Add to dashboard Cite

show abstract

“…These studies have been generously cited in the literature (e.g., Ophori 1998Ophori , 1999Lutz et al 2007;He et al 2008). The validity of several of these models has undergone critical review in the past (e.g., Konikow and Bredehoeft 1992;Jackson 1992).…”

Section: Introductionmentioning

confidence: 99%

“…It has been argued that it is possible to arrive at a reasonable match between observed and model computed heads with different sets of hydraulic parameters using this approach. The reviews of Franke and Reilly (1987), Motlyaner and Wills (1993), Ophori (1999) suggest that this approach may not be completely accurate and the results may be misleading because there is a large range of possible sets of aquifer hydraulic parameters that can result in reasonable matches between model computed and observed hydraulic heads. However, when models are carefully constructed and calibrated with data for all areas of the model domain, reasonably accurate values can be obtained for aquifer hydraulic parameters.…”

Section: Introductionmentioning

confidence: 99%

Groundwater flow modeling and particle tracking for chemical transport in the southern Voltaian aquifers

Yidana

2010

Environ Earth Sci

View full text Add to dashboard Cite

Groundwater is the major source of water supply for most uses in the rural settlements in Ghana. A groundwater flow model was calibrated for some aquifers of the southern Voltaian sedimentary system under steadystate conditions. The objective was to determine estimates of the hydraulic conductivities of the different hydrostratigraphic units of the southern Voltaian, and the distribution of recharge from precipitation. Data on the stable isotopes of oxygen and hydrogen from the study area suggest that groundwater recharge in the area is from rainfall. The calibrated steady-state model suggests that aquifer hydraulic conductivities in the study area range from 1.19 to 6.3 m/day. Hydrostratigraphic unit specific hydraulic conductivities are discussed. The calibrated recharge ranges from 3.81e-05 m/day to 6.0e-04 m/day, which represents 0.9-6% of the precipitation in the form of rainfall. Six distinct flowpaths have been defined using particle tracking. The particle tracking simulation suggests travel times in the range of 380 to 5,199 years from recharge areas to discharge areas along the flowpaths identified. A contaminant dropped at the recharge areas in the central sections of the model area would travel at these rates along the flowpaths, assuming that advection is the dominant transport process. Inverse geochemical modeling indicates the dissolution of albite, K-feldspars and anorthite, respectively, along flowpaths I and IV. The inverse modeling along flowpaths I and IV suggest the dissolution of albite, K-feldspar and anorthite, respectively, at 1.085e-06, 3.16e-08 and 3.168e-07 mmol/year.

show abstract

“…They contend that the non-uniqueness of such models lies in the fact that several different sets of data of aquifer parameters are capable of yielding the same level of calibration in models. However, it has been proven over time that when the data are sufficiently large and representative of the domain as is the case with the current study and the model is carefully calibrated (Ophori 1999), a reasonably accurate representation of the flow geometry and groundwater conditions can be achieved. Furthermore, the problem of apparent non-uniqueness is not the exclusive preserve of numerical groundwater flow models, as every system which is based on calibrated models is subject to the same limitation.…”

Section: General Groundwater Flowmentioning

confidence: 93%

“…When carefully calibrated with reliable and representative field data, it is possible to use numerical groundwater flow models to constrain aquifer parameters and their spatial variations. For instance, Ophori (1999) constrained the spatial and vertical variations in the permeability of a regional aquifer system through model calibration. A similar approach was applied by Yidana (2011a, b), Yidana et al (2012) and Attandoh et al (2013) in parts of Ghana.…”

Section: Introductionmentioning

confidence: 99%

Numerical analysis of groundwater flow and potential in parts of a crystalline aquifer system in Northern Ghana

Yidana

Alo

Addai

et al. 2015

Int. J. Environ. Sci. Technol.

View full text Add to dashboard Cite

The groundwater flow system in a crystalline aquifer system in parts of Northern Ghana was simulated and calibrated under steady-state conditions. The objective was to estimate the regional distribution of a key aquifer hydraulic parameter (the hydraulic conductivity) and recharge and also to predict possible effects of different abstraction and groundwater recharge scenarios on the sustainability of groundwater resources in the area. The study finds that the hydraulic conductivity field is quite homogeneous and has values ranging between 1.70 and 2.24 m/day. There is an apparent dominance of regional groundwater flow systems compared to local flow systems. This is probably attributed to the homogeneity in the hydraulic conductivity field and the absence of complex local relief. Estimated groundwater recharge ranges between 0.036 and 0.164 m/yr representing 3.6 and 16.4 % of the local annual precipitation, respectively. Substantial subsurface inflows and outflows have also been simulated through general head boundaries. The simulation suggests that under the current conditions of groundwater recharge estimated at calibration, the system can sustain increment in groundwater abstraction by up to 50 % without any significant changes in the groundwater flow geometry and drawdowns in the hydraulic heads. However, significant drawdowns will be expected in the wake of 100 % increment in groundwater abstraction and a reduction in recharge by 10 % during the 20-year period. Under such conditions, the flow geometry will significantly be altered and a reversal in groundwater flow will be observed.

show abstract

Constraining permeabilities in a large-scale groundwater system through model calibration

Cited by 22 publications

References 45 publications

A simulation of large‐scale groundwater flow and travel time in a fractured rock environment for waste disposal purposes

A simulation of large‐scale groundwater flow and travel time in a fractured rock environment for waste disposal purposes

Groundwater flow modeling and particle tracking for chemical transport in the southern Voltaian aquifers

Numerical analysis of groundwater flow and potential in parts of a crystalline aquifer system in Northern Ghana

Contact Info

Product

Resources

About