Conjunctive use of floodwater harvesting for managed aquifer recharge and irrigation on a date farm in Morocco

Abstract

In arid regions, harvesting floodwater can mitigate irrigation-induced groundwater depletion by providing additional surface water and recharging aquifers. We designed an experimental protocol to quantify these fluxes on a date farm located along the Wadi Satt, whose flow originates from the Anti-Atlas Mountains in south-eastern Morocco. Automatic barometric sensors were used to monitor the water level in a 6500 m³ floodwater harvesting pond and in surrounding boreholes. Six flood events occurred from 2021 to 2023. The pond water balance indicated that most stored water is pumped for irrigation (56% of harvested floodwater). More than 40% infiltrates at a rate of approximately 90 mm day⁻¹, and the remainder evaporated. Analytical modelling of the pond water table system showed that the radius of the piezometric mound resulting from pond infiltration is less than 360 m. Groundwater recharge from the irrigated plot could be observed after two close floods that enabled continuous pumping for several weeks, suggesting that in this specific context, over-irrigation using surface water allows the aquifer to be recharged. The hydrological effects of possible future expansion of these ponds at the watershed scale should be analysed to assess possible negative impacts on downstream water resources.