EVALUATING GROUNDWATER FLOW AND WATER-LEVEL OSCILLATIONS NEAR THE RING OF CENOTES,NORTHEASTERN YUCATAN, MEXICO

The Yucatan (Mexico) Peninsula's permeable karst aquifer is a critical water resource that is threatened by emerging groundwater contamination issues and rising sea level. Previous research has indicated that ocean tidal oscillations can be detected far from the Yucatan coast and have utilized these oscillations to quantify aquifer parameters. To better define the physical processes that control flow paths in the Yucatan's karst aquifer and measure the influence of ocean tides on groundwater levels, data logging pressure sensors were placed in cenotes and wells at nine locations in and around the Ring of Cenotes, a major geomorphic feature in the Yucatan. Water depths were manually measured at these and three additional locations after establishing surveyed control points using a GPS unit and an autolevel. An isolated one meter increase in groundwater level was measured south of Progreso, Mexico associated with a large precipitation even. This localized change in hydraulic head dissipated over the following month and locally altered groundwater flow patterns. Water level oscillations measured in a shallow coastal well near Progreso, Mexico did not visually match ocean tidal oscillations, suggesting that the associated aquifer is either hydraulically isolated from ocean tides or human activities have altered the aquifer, reducing hydraulic diffusivity and dampening the tidal influence. Fourier, Continuous Wavelet and Stationary Wavelet transforms have been applied to the groundwater level time series data and indicate there are water level oscillations with 12 and 24 hour periods. This analysis indicates that water level data from coastal cenotes and wells associated with the Ring Of Cenotes contain oscillations consistent with ocean tidal oscillations; however, water level oscillations measured at other stations appear to be related to atmospheric tides.