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<p>The inherent heterogeneity of aquifer systems poses substantial difficulties in delineating Hydraulic Flow Units (HFUs) and evaluating groundwater flow efficiency. This study presents an innovative approach for delineating Hydraulic Flow Units within a heterogeneous aquifer system by integrating petrophysical modeling techniques with electrostratigraphic information. A key novelty is the application of an optimized hydraulic flow unit classification framework that leverages Flow Zone Indicator and Aquifer Quality Index computations to resolve complex spatial variations in aquifer permeability. To achieve a comprehensive geophysical assessment, geoelectrical surveys were conducted at 20 sites utilizing the SAS 1000 ABEM resistivity meter. This methodological approach was adopted to facilitate high-resolution subsurface characterization. Geoelectrostratigraphic results revealed the presence of three subterranean layers interbedded with minor clay sequences. The uppermost layer (loamy topsoil) had resistivity values in the range of 0.4–52.8 Ωm, while the layer thickness ranged from 0.5 to 4.0&#xa0;m. Directly underlying this was fine sand, characterized by resistivity values spanning 1.1–26.0 Ωm, with thickness ranging from 1.4 to 45.0&#xa0;m. The third layer (gravelly sand) had resistivity values in the range of 3.5–1822.5 Ωm. Aquifer hydraulic conductivity ranged from 6.81 × 10–6 to 6.47 × 10–4&#xa0;m/s, permeability ranged from 965.9137 to 91,753.53 mD, tortuosity ranged from 0.570 to 1.027, Aquifer Quality Index values ranged from 1.85 to 6.13, and Flow Zone Indicator values ranged from − 3.58 to 4.86. The Stratigraphic Modified Lorenz Plot identified three hydrostratigraphic flow units, each exhibiting unique flow behaviors. The first flow unit was classified as a superconductor; the second and third flow units were classified as conductors with fair flow efficiency ranking. The study also highlighted the pronounced heterogeneity of the aquifer system, evidenced by a Dykstra-Parsons coefficient of 1. This heterogeneity, resulting from the interbedding of variable sand grain sizes within the saturated layers, directly impacts groundwater recharge, contamination transport, and water resource management strategies. The results of this research offer important insights for optimizing borehole placement, improving groundwater extraction strategies, and mitigating potential aquifer depletion. These results also enhance permeability prediction in highly heterogeneous coastal aquifers and provide a systematic methodology applicable to diverse water reservoir systems. </p>

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Hydrogeophysical characterization of unconsolidated aquifers: an application of Stratigraphic Modified Lorenz Plots and Flow Zone Indicators for groundwater management

  • 期刊论文

  • 发表日期：

    2025年4月28日

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  • N. I. Udosen

摘要

The inherent heterogeneity of aquifer systems poses substantial difficulties in delineating Hydraulic Flow Units (HFUs) and evaluating groundwater flow efficiency. This study presents an innovative approach for delineating Hydraulic Flow Units within a heterogeneous aquifer system by integrating petrophysical modeling techniques with electrostratigraphic information. A key novelty is the application of an optimized hydraulic flow unit classification framework that leverages Flow Zone Indicator and Aquifer Quality Index computations to resolve complex spatial variations in aquifer permeability. To achieve a comprehensive geophysical assessment, geoelectrical surveys were conducted at 20 sites utilizing the SAS 1000 ABEM resistivity meter. This methodological approach was adopted to facilitate high-resolution subsurface characterization. Geoelectrostratigraphic results revealed the presence of three subterranean layers interbedded with minor clay sequences. The uppermost layer (loamy topsoil) had resistivity values in the range of 0.4–52.8 Ωm, while the layer thickness ranged from 0.5 to 4.0 m. Directly underlying this was fine sand, characterized by resistivity values spanning 1.1–26.0 Ωm, with thickness ranging from 1.4 to 45.0 m. The third layer (gravelly sand) had resistivity values in the range of 3.5–1822.5 Ωm. Aquifer hydraulic conductivity ranged from 6.81 × 10–6 to 6.47 × 10–4 m/s, permeability ranged from 965.9137 to 91,753.53 mD, tortuosity ranged from 0.570 to 1.027, Aquifer Quality Index values ranged from 1.85 to 6.13, and Flow Zone Indicator values ranged from − 3.58 to 4.86. The Stratigraphic Modified Lorenz Plot identified three hydrostratigraphic flow units, each exhibiting unique flow behaviors. The first flow unit was classified as a superconductor; the second and third flow units were classified as conductors with fair flow efficiency ranking. The study also highlighted the pronounced heterogeneity of the aquifer system, evidenced by a Dykstra-Parsons coefficient of 1. This heterogeneity, resulting from the interbedding of variable sand grain sizes within the saturated layers, directly impacts groundwater recharge, contamination transport, and water resource management strategies. The results of this research offer important insights for optimizing borehole placement, improving groundwater extraction strategies, and mitigating potential aquifer depletion. These results also enhance permeability prediction in highly heterogeneous coastal aquifers and provide a systematic methodology applicable to diverse water reservoir systems.