A high measurement frequency based assessment of shallow groundwater fluctuations in Metouia Oasis, South Tunisia

概要

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The Metouia Oasis (South Tunisia) is increasingly being impacted by high soil salinity, leading to yield losses and ultimately to farmland abandon. In this area shallow groundwater rise is considered the major factor responsible for salt accumulation in soils. However, limited data exist on groundwater fluctuations in Metouia Oasis, despite the criticality of such information for accurate soil salinity assessment. In this study, groundwater behavior was monitored at a high measurement frequency. An observation well was installed and equipped with a water level sensor (Diver DI240, Van Essen Instrument) to record the groundwater fluctuation at 30 minute intervals. The results showed that at seasonal basis, groundwater was characterized by a declining phase during spring and summer seasons followed by a rising phase starting from mid-October. Further, the hydrograph was characterized by several rapid water table rises following recharge events followed by extended periods of water table decline. The hourly observations at daily basis displayed strong evidence of diurnal effects on groundwater patterns. The results from this study suggest that consideration should be given to monitoring water table behavior in Metouia Oasis more frequently in order to capture daily and seasonal patterns.