Abstract
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.