Water-level fluctuation and its implication on the hydrologic cycle in the Gwangneung Supersite, Korea

For effective assessment and management of water resources, it is important to understand and quantify each component of the hydrologic cycle. A careful and detailed analysis of spatio-temporal variations in water levels in aquifers could reveal useful information on the groundwater system. This study is objected to understand the reasons and mechanisms of fluctuations. As a part of an interdisciplinary research project, HydroKorea, to ascertain the water cycle quantitatively, water levels have been monitored from shallow monitoring wells(G1, G4) with less than 1-m in depths and a deep well enclosing three monitoring wells (ft1, ft2 and ft3 screened at depths of 102m, 45m and 6m below ground surface, respectively). Monitoring wells are located in the Gwangneung Supersite, Korea. Water levels used in this study were monitored by 10-min interval from February to May in 2007. Water levels compensated for air pressure were analyzed using a Fast Fourier Transform(FFT) technique for power spectral analysis. Results show periodic variations in 11.38, 12.19, 21.33, 24.38, and 28.44 hours, indicating strong influence of diurnal and semidiurnal tidal components. The diurnal components of the water levels from G1 and G4 in summer had greater power than those in winter, implying that the water table is affected by not only earth tides but evapotranspiration. However, those of the water levels from ft1, ft2 and ft3 do not show seasonal characteristics indicating that evapotranspiration has no influence in water levels of deep monitoring wells.