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Article Dans Une Revue Hydrological Processes Année : 2020

Groundwater recharge sources in semiarid irrigated mountain fronts

Résumé

High-elevation mountains often constitute for basins important groundwaterrecharge sources through mountain-front recharge processes. These processes includestreamflow losses and subsurface inflow from the mountain block. However, anotherkey recharge process is from irrigation practices, where mountain streamflow is distrib-uted across the irrigated piedmont. In this study, coupled groundwater fluctuationmeasurements and environmental tracers (18O,2H, and major ions) were used to iden-tify and compare the natural mountain-front recharge to the anthropogenically inducedirrigation recharge. Within the High Atlas mountain front of the Ourika Basin, CentralMorocco, the groundwater fluctuation mapping from the dry to wet season showedthat recharge beneath the irrigated area was higher than the recharge along thestreambed. Irrigation practices in the region divert more than 65% of the stream water,thereby reducing the potential for in-stream groundwater recharge. In addition, the irri-gation areas close to the mountain front had greater water table increases (up to3.5 m) compared with the downstream irrigation areas (<1 m increase). Upstream cropshave priority to irrigation with stream water over downstream areas. The latterare only irrigated via stream water during large flood events and are otherwisesupplemented by groundwater resources. These changes in water resources used forirrigation practices between upstream and downstream areas are reflected in the spa-tiotemporal evolution of the stable isotopes of groundwater. In the upstream irrigationarea, the groundwater stable isotope values (δ18O:−8.4‰to−7.4‰) reflect rechargeby the diverted stream water. In the downstream irrigation area, the groundwaterisotope values are lower (δ18O:−8.1‰to−8.4‰) due to recharge via the flood water.In the nonirrigation area, the groundwater has the highest stable isotope values(δ18O:−6.8‰to−4.8‰). This might be due to recharge via subsurface inflow fromthe mountain block to the mountain front and/or recharge via local low altitude rainfall.These findings highlight that irrigation practices can result in the dominant mountain-front recharge process for groundwate
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Dates et versions

hal-03956609 , version 1 (25-01-2023)

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Houssne Bouimouass, Younes Fakir, Sarah Tweed, Marc Leblanc. Groundwater recharge sources in semiarid irrigated mountain fronts. Hydrological Processes, 2020, 34 (7), pp.1598-1615. ⟨10.1002/hyp.13685⟩. ⟨hal-03956609⟩
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