Monitoring the Mnasra groundwater quality regarding nitrate-related pollution. Gharb region-Morocco. 2011-2012

Water pollution by nitrate has become increasingly a serious problem in Mediterranean countries. Agricultural activities are probably the most significant anthropogenic sources of nitrate contamination in groundwater. Irrigation system is among the causes behind leaching of nitrate from soil surface to groundwater. Gharb plain is the largest agriculture irrigated zone in northwest of Morocco, well known for its intensive agricultural activities. The excessive use of fertilizers and manure under gravity irrigation system, presents a huge risk to groundwater quality especially for sandy-loam soils similar to those of the area. The purpose of the present study was the evaluation of the level of nitrate contamination in groundwater, and the attempt to relate it to the irrigation system adopted in Gharb area. A total of 90 water samples were collected and analyzed by ionic chromatography. Results showed that 86.7% of water samples have exceeded (54 - 400 mg/L) the limit of nitrate concentration (50 mg/L) fixed by World Health Organization (WHO). Attempts to focus on the main physical and chemical factors behind the magnitude of contamination are discussed.