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Seasonality in intermittent streamflow losses beneath a Semiarid Wadi
  • Younes Fakir,
  • Houssne BOUIMOUASS,
  • Jim Constantz
Younes Fakir
University Cadi Ayyad

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University Cadi Ayyad
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Jim Constantz
United States Geological Survey
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Streamflow losses beneath non-perennial streams are potentially a major contribution to recharge, though measurements are often challenging due to the transient nature of these non-continuous (both spatially and temporally) streamflow. Significant investigative efforts for ephemeral streams have been described in literature, yet streams with intermittent streamflows lack this level of effort, particularly over an entire hydrological cycle. In this study, streambed water content and temperature were continuously logged over a year for an intermittent stream under semi-arid conditions in a wadi (arroyo) in Central Morocco. The results show that streambed water content and temperature are complementary data for identifying and classifying infiltration events, with respect to determining their duration, depth of water content increase and flow velocity within the sediments. Water content measurements easily allow distinguish between downward surface water percolation as well as upward groundwater wetting front. Over the entire year, the calculated total potential recharge based on temperature modeling was 425 mm. During winter and spring when the alluvium has a higher water moisture, this recharge is predominantly generated by floods. Normal streamflow generally generates low infiltration but contributes to wetting the sediment. During the summer, brief flashfloods over dry sediment result in shallower and slow wetting from infiltration, despite of their higher peak streamflows. Thus, for this wadi, there is clear seasonality (seasonal variation) in relations between amounts of streamflow, streamflow loss and depth of wetting into the streambed, as well as upward advance of wetting through deeper streambed sediments from groundwater receiving lateral mountain-front recharge.