Evaluation of nitrate source and its distribution in the groundwater of Essaouira basin

Abstract

Groundwater resources in Morocco are expected to decline over the next decades due to increasing drainage for rural and urban development and decreasing internal recharge through precipitation under the influence of climate change. In addition to water scarcity, Morocco is suffering deterioration in groundwater quality as a result of groundwater depletion. The aim of this research is to obtain a better understanding of electrical conductivity and nitrate distributions in the aquifers during a period of 12 years on Essaouira basin (southwestern Morocco) to communicate the negative effects of nitrate contamination in groundwater systems to water experts, decision makers as well as the general public. The results obtained indicate that the spatiotemporal distribution map of the electrical conductivity is become very improved from 2007 to 2019 (1935–2454 μS/cm), and the NO3 concentrations ranged from 2 to 214 mg/L based on 196 groundwater samples. These highest nitrate concentrations could be explained by: (1) the high concentration of fertilizers use; (2) the gap of a sewage system and wastewater treatment plant; (3) the tourist effect; (4) the absence of a sanitation network allowing the evacuation of wastewater; (5) poor protection of wells and especially against the permanent puddles surrounding the structures which are heavily loaded with excrement from animals coming for watering and also for the water supply of the inhabitant. Consequently, the development of a geoethical approach is an essential aspect to reduce the demand and the use of water by the inhabitants of the research region. The geoethical method has the potential to reduce the use of nitrogen fertilizers and help in the management of groundwater resources in the Essaouira basin.