Groundwater recharge sources in semiarid irrigated mountain fronts

Abstract

High‐elevation mountains often constitute for basins important groundwater recharge sources through mountain‐front recharge processes. These processes include streamflow losses and subsurface inflow from the mountain block. However, another key recharge process is from irrigation practices, where mountain streamflow is distributed across the irrigated piedmont. In this study, coupled groundwater fluctuation measurements and environmental tracers (18O, 2H, and major ions) were used to identify and compare the natural mountain‐front recharge to the anthropogenically induced irrigation recharge. Within the High Atlas mountain front of the Ourika Basin, Central Morocco, the groundwater fluctuation mapping from the dry to wet season showed that recharge beneath the irrigated area was higher than the recharge along the streambed. 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 irrigation areas close to the mountain front had greater water table increases (up to 3.5 m) compared with the downstream irrigation areas (<1 m increase). Upstream crops have priority to irrigation with stream water over downstream areas. The latter are only irrigated via stream water during large flood events and are otherwise supplemented by groundwater resources. These changes in water resources used for irrigation practices between upstream and downstream areas are reflected in the spatiotemporal evolution of the stable isotopes of groundwater. In the upstream irrigation area, the groundwater stable isotope values (δ18O: −8.4‰ to −7.4‰) reflect recharge by the diverted stream water. In the downstream irrigation area, the groundwater isotope 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 from the 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 groundwater.

Evaluation of the Drivers Responsible for Flooding in Africa

“…In Maghreb countries, stations are located close to the margins of the Sahara Desert, where flood generating processes are hardly captured at the daily time step (El Khalki et al., 2020). In addition, these basins are prone to be disturbed by human activities, such as water withdrawals for irrigation, even if the presence of large dams or reservoirs is not reported (Bouimouass et al, 2020).…”

Soil NO3− storage from oasis development in deserts: Implications for the prevention and control of groundwater pollution

“…This would suggest that the δ 2 H and δ 18 O values have also influenced by the infiltration recharge of irrigation water. These findings highlight the recharge effect of irrigation on groundwater in semiarid, irrigated mountain‐fronts (Bouimouass, Fakir, Tweed, & Leblanc, 2019). The δ 2 H and δ 18 O values in the JD sample, which is located in the northern sector of the Wuwei Basin, deviated from the LMWL and were higher than the δ 2 H and δ 18 O values for the Wuwei Basin (Figure 9), indicating that the groundwater has not been affected by modern plain atmospheric precipitation, but rather by precipitation and meltwater from the Qilian Mountains, although the evaporation of alluvial aquifers and river feeding are also important (Bresciani et al, 2018).…”

ADHI: the African Database of Hydrometric Indices (1950–2018)

“…The database used in the present work is based on the collection of stations from the Global Runoff Data Center (GRDC) and the SIEREM database (Boyer et al, 2006;Dieulin et al, 2019). The hydro-climatological data contained in SIEREM are the legacy of the former Laboratoire d'Hydrologie of the Office de la recherche scientifique et technique outre-mer (ORSTOM; now Institut de Recherche pour le Développement, IRD, France).…”

“…For these basins, a manual procedure with the Arcmap ® software has been implemented to delineate the catchment boundaries from flow di- rection maps. In addition, for several hundred catchments it was possible to compare the results of the catchment delineation procedure with the catchment areas available in the SIEREM database and the ORSTOM reports (available online at the address: https://horizon.documentation.ird.fr, last access: 13 April 2021), which have been most often individually delineated and carefully checked from ground knowledge over the years (Boyer et al, 2006).…”