Abstract

Fractured crystalline aquifer is considered as the main source of water supply in most of the arid and semi-arid regions. Fractures play an essential role as pathways through which groundwater flows from high catchments to supply the productive wells in lowlands. The hydraulic conductivity measurements for highly fractured crystalline aquifers are a must for optimal management of groundwater extraction from these aquifers. The current work aims at estimating the hydraulic conductivity of the crystalline aquifer by using an unconventional approach based entirely on the processing of remotely-sensed lineament data and field observations. Extracted lineaments at four sites near the productive wells along Wadi Nasab area (WNA) were traced from Landsat (ETM+7) and other ancillary geological data by using image processing and GIS tools. Hence, four discrete fracture networks (DFN) were designed and practiced for the selected test sites to model the groundwater flow through the fracture system in order to estimate the hydraulic conductivity of the investigated crystalline aquifer. The achieved results indicated that the hydraulic conductivity of fractured basement aquifer of WNA varied between 2.3 × 10⁻⁷ and 6.1 × 10⁻⁷ m/s. The estimated hydraulic conductivity values are close to the values of previous field infiltration tests in the nearby area at Sinai. The previously estimated infiltration rates (expressing the vertical hydraulic conductivity) on the fractured crystalline outcrops ranged between 2.6 × 10⁻⁶ and 6.5 × 10⁻⁷ m/s, which are concordant with achieved results. Moreover, the achieved values match the previously published values of hydraulic conductivity for similar crystalline aquifers around the world, reflecting the high validity of the used unconventional, low-cost approach to estimate the hydraulic conductivity of fractured crystalline aquifers. The designed approach can be potentially practiced on similar basins in Sinai peninsula and other comparable basins having similar geological and climatic environments around the world.

Research Highlights

• Estimating the hydraulic conductivity of fractured crystalline aquifer by using remotely sensed lineament data and field observations.

• Discrete fracture networks (DFN) models the groundwater flow to estimate the hydraulic conductivity of the crystalline aquifer.

• The estimated hydraulic conductivity values are varied between 2.3 × 10-7 m/s and 6.1×10-7 m/s, which come in agreement with the previously estimated values using the conventional infiltration tests.

• The results reflect the validity of using this unconventional and low-cost approach to estimate the hydraulic conductivity of fractured crystalline aquifers.

中文翻译：

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利用遥感和现场数据分析估算裂缝性含水层中的水力传导率：以埃及南西奈的Wadi Nasab地区为例

摘要

在大多数干旱和半干旱地区，破裂的含水层被认为是主要的水源。裂缝是地下水从高流域流向低地生产井的主要途径。要对从这些含水层中抽取的地下水进行最佳管理，必须对高度破裂的结晶含水层进行水力传导率测量。当前的工作旨在通过完全基于遥感的岩相数据处理和现场观测的非常规方法来估算结晶含水层的水力传导率。通过使用图像处理和GIS工具，从Landsat（ETM + 7）和其他辅助地质数据中追踪了Wadi Nasab地区（WNA）沿生产井附近四个地点的提取岩层。因此，为选定的测试点设计并实施了四个离散裂缝网络（DFN），以模拟流过裂缝系统的地下水，以估算所研究的结晶含水层的水力传导率。取得的结果表明，WNA裂缝性地下含水层的水力传导率在2.3×10之间变化。^-7和6.1×10 ^-7 m / s。估计的水力传导率值接近西奈附近地区先前的现场渗透测试的值。先前估计的在破裂的晶体露头上的渗透率（表示垂直水力传导率）在2.6×10 ^-6和6.5×10 ^-7之间m / s，与取得的结果一致。此外，所获得的值与世界各地类似的结晶含水层的水力传导率的先前公布值相符，这反映了所使用的非常规，低成本方法来估算裂隙结晶含水层的水力传导率的高度有效性。设计的方法可以在西奈半岛的类似盆地和其他在世界范围内具有相似地质和气候环境的类似盆地中实践。

研究重点

• 通过使用遥感线性数据和现场观测，估算裂缝性结晶含水层的水力传导率。

• 离散裂缝网络（DFN）对地下水流进行建模，以估算结晶含水层的水力传导率。

• 估计的水力传导率值在2.3×10-7 m / s和6.1×10-7 m / s之间变化，这与使用常规渗透测试得出的先前估计值一致。

• 结果反映了使用这种非常规且低成本的方法来估算裂缝性结晶含水层的水力传导率的有效性。