ESTIMATION OF GROUNDWATER RECHARGE IN ARID REGION THROUGH HYDROCHEMISTRY AND ISOTOPE A CASE STUDY KOURIMAT BASIN MOROCCO

Abstract

ABSTRACT Morocco is classified as an arid to semi-arid country with a population according to 2013 estimates of 35 million inhabitants and a growth rate of 1,4 %. Efficient use of Morocco’s scarce water is becoming increasingly important as the urban population grows. This study concerns the groundwater recharge in the Kourimat basin and describes a combined methodology for groundwater recharge estimation in Morocco, through the isotopic and hydrochemical approaches. Groundwater samples from Essaouira basin, east Morocco, falls along the Global Meteoric Water Line (GMWL), and below the Local Meteoric Water Line (LMWL), suggesting that the waters have been recharged under a different climatic regime, different from today. Water isotopic composition shows low evaporation of precipitations during infiltration. Depletion in heavy isotopes is the characteristic of mountain rainfalls or of a climate colder and wetter than present at the research area. Carbon-14 activities (30 – 60 pMC) indicate a long residence time. Tritium levels in the groundwater of the Kourimat Basin are below the detection limit (<1.5 TU). Five groundwater samples in South-West of Essaouira city, presents tritium content between 1 and 3 TU.