Irrigated agriculture in (semi-)arid regions may exert serious pressures on groundwater resources and jeopardise further agricultural and socio-economical developments. For assessing these pressures, we present in this paper results from a groundwater quality survey performed in 2005 within the irrigated agricultural Triffa plain in north-east Morocco. The study focuses on the physico-chemical and bacteriological quality of the groundwater body within the plain and exploits the correlation and spatial dependency of the quality parameters. It is demonstrated that the water quality in this region is critical. Nitrate levels are situated between 2 and 153 mg/l, with 73% of the observations exceeding the critical level of 50 mg/l. Nitrite, ammonia, orthophosphate and dissolved organic matter content do not exceed existing norms. Bacteriological residues (faecal, total coliforms, faecal streptococcus and clostridium sulfido-reductants), however, are retrieved in nearly all water samples. Bacteriological contamination is merely correlated with nitrite and ammonia content rather than with nitrate content, indicating a possible contribution of local pollution sources to groundwater deterioration. The variability of the nitrate and bacteriological pollution is important and spatially correlated. The spatially dependency is modelled using spherical and Gaussian semi-variograms and is used to map the nitrate and bacteriological contamination using ordinary kriging techniques. The results shown are significantly different as compared to earlier studies on groundwater quality for the studied aquifer. The differences may be explained partially by modified but inappropriate fertilizer management practices in combination with intensive irrigation. Given the agricultural developments in this area, further deterioration of the groundwater quality is expected if no mitigation strategies are developed.
Water resources in Morocco are currently under serious pressure. National averaged available water resources are estimated to be equal to 971 m3/habitant/year. Morocco thereby ranks on the 155th position on a scale of 180 countries, measuring the pressure that is exerted on available fresh water resources. The volume of available groundwater in Morocco is estimated to be equal to 4 × 109 m3/year. Groundwater resources are distributed within 32 profound and 46 superficial major groundwater bodies. Groundwater complements the 20 × 109 m3/year of available surface water and is therefore an essential resource that should appropriately be protected.
Irrigated agriculture is responsible for 93% of the total water demand in Morocco. Irrigated agriculture is also the principal driver for ensuring food security and economical development. Yet, the irrigated agricultural in Morocco is also reported to have negative impacts on groundwater quality for instance observed high nitrate contamination of groundwater in the central Moroccan Essaouira basin and explained this contamination by an intensifying agricultural activity. studied the groundwater quality in the Tadla plain for the period of August 1996 until April 1998. He reported nitrate contamination levels which varies between 3 and 228 mg/l for the Beni Amir part in the north of the plain and between 6 and 152 mg/l for the Beni Moussa part in the south of this plain. Similar observations have been made in Algeria. For instance, a study carried out jointly from 1990 to 1993 by the National Agency of the Hydrological Resources (ANRH) and the University of Blida, revealed the presence of critical levels of underground pollution of waters by nitrates in the area of High Chéliff and the Plain of Mitidja. The content of nitrates in this water sometimes reaches the level of 200–270 mg/l, which greatly exceeds the threshold of 50 mg/l fixed by the standards of the World Health Organization (WHO) for drinking water.
Unfortunately, most of the previous studies in this region focused only on one singular groundwater quality parameter, typical nitrate or total salinity. Previous studies did not allow to assess the overall water quality in holistic way, encompassing thereby as well physico-chemical, organic and micro-biological quality criteria. The potential correlation which may exist between quality parameters is further rarely explored, inasmuch as their space-time dynamics. The mapping of groundwater quality is therefore often subjected to a lot of uncertainty, which complicates the assessment of the overall quality of the groundwater body itself. We also observe that only few studies have been reported illustrating these problems for the coastal aquifers in the north-eastern part of Morocco.
This paper therefore envisages to illustrate the possible impact of irrigated agriculture on as well physico-chemical and bacteriological groundwater quality parameters for the Triffa aquifer. This aquifer is a major groundwater body of the Moulouya catchment, situated in north-east Morocco. The study focuses on nutrient related and bacteriological quality parameters of the groundwater body. The former parameters are well known to be related to fertilization and organic matter management practices within agro-ecosystems. Potential problems may be expected for nutrient related parameters since an inquiry conducted by the local administration responsible for agricultural development elucidated that 92% of the farmers in the area use fertilizer dosages which exceed the recommended levels. The latter parameters are further closely linked to health and sanitation problems.
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