Assessment of recharge to the coastal Bou-Areg aquifer (Morocco) using environmental tracers.

English Abstract:

Located in NE Morroco, the coastal Bou-Areg aquifer provides an illustration of hydrogeological consequences of the rapid development of irrigated agriculture in semi arid mediterranean areas. The main features are a saline water intrusion in the coastal zone, and elevated nitrate concentrations in agricultural areas, as a consequence of excessive withdrawals and increased recharge through irrigation return flow, respectively. While, the aquifer is expected to receive fresh water from lateral recharge, the dissolution of messinian evaporites may provide another source for salinity. Here, more than elsewhere understanding the origin of groundwater and the global recharge pattern is a fundamental step for a sustainable groundwater management. To this end, eleven samples were collected in September 2014 for young-aged radiogenic (³H), old-aged radiogenic (¹⁴C) and stable (¹³C, ²H, ¹⁸O) isotopes combined with additional young-age (SF_6, CFCs) tracers and noble gases (Xe, Ar, Kr, Ne). Preliminary results allow to distinguish between at least two groundwater masses, to estimate recharge rates in the plain and to provide insights on lateral groundwater inputs from the surrounding mountainous areas.