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<p>Groundwater level (GWL) fluctuations and flow system dynamics were investigated across diverse topographic and geological settings in the volcanic highlands of Ethiopia. GWLs were monitored with automatic pressure transducers in both shallow and deep boreholes, and manually in hand-dug wells. Concurrently, water samples were collected for major ion chemistry and stable isotope analysis to delineate the groundwater flow system characteristics and dynamics. GWLs rise during the rainy season and recede during the dry season. However, GWLs in some deep boreholes rise later in the dry season, indicative of confined aquifers that are recharged from distal areas. During the dry season, certain deep boreholes displayed distinctive daily GWL fluctuation phases due to earth tides, characterized by amplitudes ranging from 2 to 3&#xa0;cm in one phase and &lt; 1&#xa0;cm amplitude fluctuations in the second phase. Spectral analysis identified four main tidal periods: M2, S2, K1, and O1, with M2 and S2 being the most dominant. Quantitative tidal analysis further indicated that GWL dynamics in some deep boreholes reflect a semi-confined aquifer system. Hydrochemistry and isotope data demonstrated that groundwater evolves from rapidly circulating, Ca-HCO<sub>3</sub> groundwaters in recharge areas to highly evolved Na-HCO<sub>3</sub> and Mg-Ca-Na-HCO<sub>3</sub> groundwaters in discharge areas. A conceptual groundwater flow model was developed from the integrated approach, revealing three distinct flow systems: shallow, intermediate, and deep. A comprehensive understanding of the groundwater response to hydrological processes and anthropogenic activities is essential for effective groundwater resources management.</p>

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Temporal variability of groundwater levels and flow system dynamics in the semi-humid tropical volcanic highlands of Ethiopia

  • 期刊论文

  • 发表日期：

    2025年8月2日

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  • Fenta Nigate,
  • Alemu Yenehun,
  • Ashebir Sewale Belay,
  • Desale Kidane Asmamaw,
  • Elias Sime,
  • Kristine Walraevens

摘要

Groundwater level (GWL) fluctuations and flow system dynamics were investigated across diverse topographic and geological settings in the volcanic highlands of Ethiopia. GWLs were monitored with automatic pressure transducers in both shallow and deep boreholes, and manually in hand-dug wells. Concurrently, water samples were collected for major ion chemistry and stable isotope analysis to delineate the groundwater flow system characteristics and dynamics. GWLs rise during the rainy season and recede during the dry season. However, GWLs in some deep boreholes rise later in the dry season, indicative of confined aquifers that are recharged from distal areas. During the dry season, certain deep boreholes displayed distinctive daily GWL fluctuation phases due to earth tides, characterized by amplitudes ranging from 2 to 3 cm in one phase and < 1 cm amplitude fluctuations in the second phase. Spectral analysis identified four main tidal periods: M2, S2, K1, and O1, with M2 and S2 being the most dominant. Quantitative tidal analysis further indicated that GWL dynamics in some deep boreholes reflect a semi-confined aquifer system. Hydrochemistry and isotope data demonstrated that groundwater evolves from rapidly circulating, Ca-HCO3 groundwaters in recharge areas to highly evolved Na-HCO3 and Mg-Ca-Na-HCO3 groundwaters in discharge areas. A conceptual groundwater flow model was developed from the integrated approach, revealing three distinct flow systems: shallow, intermediate, and deep. A comprehensive understanding of the groundwater response to hydrological processes and anthropogenic activities is essential for effective groundwater resources management.