Dynamics of groundwater recharge near a semi-arid Mediterranean intermittent stream under wet and normal climate conditions
Résumé
In semiarid and arid stream-dominated hydrosystems, the temporal variability of groundwater recharge is not widely addressed. It still holds various questions about the sources of recharge, its patterns, and the appropriate measuring technics. Hence, the main objective of the present study was to assess the changes that might affect the pattern of recharge under wetter than normal surface water availability. To this aim, water table fluctuation (WTF) was monitored near an intermittent stream in a piedmont area, over two years (2014-2016) with different conditions: extreme wet and typical weather. The groundwater recharge was assessed using the Episodic Master Recession (EMR) algorithm. During the two years, the recharge pattern was dominated by episodic events and by a high seasonality from wet seasons to dry seasons. In the wet year (2014-2015) the highest recharge was recorded following an extreme flood, which has deeply replenished groundwater. Furthermore, an exceptional steady state of groundwater level took place induced by a steady recharge rate. For several events, the assessed recharges were multisource, mainly from streamflow at local scale, but possibly from precipitation, underflow, deep percolation or irrigation return, from the upstream part of the system. The local recharge by streamflow is likely to be short-lived and the lateral recharge is likely to last longer. Consequently, the EMR algorithm estimated the total recharge that could encompass various sources. More research works and multidisciplinary approaches should be carried out to partition those sources and determine their specific contribution. In semiarid stream-dominated systems, different recharge patterns induced by extreme hydrological events (e.g. wet events) and various potential sources of recharge are to consider when assessing and predicting groundwater recharge.
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