Large areas of Morocco require irrigation and although good quality water is available in dams, farmers augment river water with poorer quality ground water, resulting in salt build‐up without a sufficient leaching fraction. Implementation of management plans requires baseline reconnaissance maps of salinity. We developed a method to map the distribution of salinity profiles by establishing a linear regression (LR) between calculated true electrical conductivity (σ, mS/m) and electrical conductivity of the saturated soil‐paste extract (ECe, dS/m). Estimates of σ were obtained by inverting the apparent electrical conductivity (ECa, mS/m) collected from a 500‐m grid survey using an EM38. Spherical variograms were developed to interpolate ECa data onto a 100 m grid using residual maximum likelihood. Inversion was carried out on kriged ECa data using a quasi‐3d model (EM4Soil software), selecting the cumulative function (CF) forward modelling and S2 inversion algorithm with a damping factor of 3.0. Using a ‘leave‐one‐out cross‐validation' (LOOCV), of one in 12 of the calibration sites, the use of the q‐3d model yielded a high accuracy (RMSE = 0.42 dS/m), small bias (ME = −0.02 dS/m) and Lin's concordance (0.91). Slightly worse results were obtained using individual LR established at each depth increment overall (i.e. RMSE = 0.45 dS/m; ME = 0.00 dS/m; Lin's = 0.89) with the raw EM38 ECa. Inversion required a single LR (ECe = 0.679 + 0.041 × σ), enabling efficiencies in estimating ECe at any depth across the irrigation district. Final maps of ECe, along with information on water used for irrigation (ECw) and the characterization of properties of the two main soil types, enabled better understanding of causes of secondary soil salinity. The approach can be applied to problematic saline areas with saline water tables.
Morocco has arid and semiarid climates. Irrigation is an imperative for agriculture. Skhirat region is known for the production of vegetables. Intensive peri-urban agriculture is associated with inconsiderate pumping of groundwater, and water becomes less abundant and of poor quality resulting in degradation of soil and water quality. Therefore, the objective of this research work was the assessment of the quality of irrigation water. The study site is located in a coastal area and dedicated to intensive land use for growing vegetables in a peri-urban agricultural zone. Monitoring of physicochemical parameters of water was carried out in 77 wells. Parameters like pH, electrical conductivity, and piezometric level were measured in situ while others like total dissolved solids and ionic balance were measured in laboratory whereas other parameters were calculated from those measured. Results showed that Na and Ca are predominant cations while Cl and SO4 are predominant anions. Piper diagram reveals two facies: sodic and calcic chlorinated. Regarding the permeability index, all wells are suitable for irrigation. The US Salinity Laboratory (USSL) diagram reveals that irrigation water has high salinization risk and low to medium alkalinization risk. The groundwater in the region is classified as very hard category; however, it does not present any risk of sodicity. These waters have a high risk of toxicity to chloride ions. In summary, although the groundwater in the Skhirat region presents a high risk of salinization, it is of good quality suitable for irrigation. Agricultural practices should be well managed to secure safe use of the water resource for a sustainable development of the agriculture in the region.
In many parts of the world, the impact of open landfills on soils, biosphere, and groundwater has become a major concern. These landfills frequently generate pollution plumes, the contours of which can be delineated by non-intrusive geophysical measurements, but in arid environments, the high soils resistivity is usually an obstacle, which results in the low number of studies that have been carried out there. In addition, such prospecting using geophysical techniques do not provide information on the intensity of the processes occurring in the water table. This study was carried out on an uncontrolled landfill in the arid Tadla plain, Morocco’s main agricultural region. A survey based on geo-referenced spontaneous potential measurements was combined with measurements of anoxic conditions (Eh-pH and O2 equilibrating partial pressure) in the groundwater and leachates, in order to highlight a pollution plume and its geometry. The range of spontaneous potential measurement is wide, reaching 155 mV. Ponds of leachate with high electrical conductivity (20 to 40 mS cm−1) form within the landfill, and present very reducing conditions down to sulphate reduction and methanisation. The plume is slowly but continuously supplied with these highly reducing and organic carbon-rich leachates from the landfill. Its direction is towards N-NW, stable throughout the season, and consistent with local knowledge of groundwater flow. The fast flow of the water table suggests pollution over long distances that should be monitored in the future. The results obtained are spatially contrasting and stable, and show that such techniques can be used on a resistive medium of arid environments.
Surface water is used for a variety of purposes, including agriculture, drinking water, and other services. Therefore, its quality is crucial for irrigation, human welfare, and health. Thus, the main objective is to improve surface water quality assessment and geochemical analysis to evaluate anthropogenic activities’ impact on surface water quality in the Oued Laou watershed, Northern Morocco. Thirteen surface water samples were characterized for 26 physicochemical and biological parameters. In this aspect, emerging techniques such as multivariate statistical approaches (MSA), water quality indices (WQI), irrigation water quality (IWQI), and Geographic Information System (GIS) were employed to identify the sources of surface water pollution, their suitability for consumption, and the distribution of surface water quality. The results showed that the major ion concentrations were reported in the following order: Ca2+, Na+, Mg2+, and K+; and HCO3− > CO32− > Cl− > SO42− > NO3− > F− > PO43− > NO2−. It was also demonstrated that almost all parameters had concentrations lower than World Health Organization (WHO) limits, except for bicarbonate ions (HCO3−) and the biochemical oxygen demand for five days (BOD5), which exceeded the WHO limits at 120 mg/L and 3 mg/L, respectively. Furthermore, the types of Ca2+-HCO3− (Calcium-Bicarbonate) and Ca2+-Mg2+-HCO3− (Calcium-Magnesium-Bicarbonate) predominated in surface water. The Principal Component Analysis (PCA) indicates that the Oued Laou river was exposed to two forms of contamination, the first being attributed to anthropogenic activities such as agriculture, while the second reflects the water-sediment interaction. The Hierarchical Cluster Analysis (HCA), reflecting the mineralization in the study area, has classified the samples into four clusters. The Inverse Distance Weighting (IDW) of the WQI indicates that 7.69% and 38.46% of the surface water represent, respectively, excellent and good quality for drinking. At the same time, the IWQI revealed that 92.30% of the water surface is good for irrigation. As a result, the combination of WQIs, PCA, IWQI, and GIS techniques is effective in providing clear information for assessing the suitability of surface water for drinking and its controlling factors and can also support decision-making in susceptible locations such as the Oued Laou river in northern Morocco.
Many methods for assessing the vulnerability of groundwater against anthropogenic pollution have been developed in the past decades. However, if aquifer vulnerability concept is well defined and the methods have been constantly tested and compared, the problem of the choice of the best method remains. The choice of the method depends on a series of factors, including the scale of the problem, the hydrogeological characteristics of the area and data availability. From a pile of a vulnerability assessing methods, the GOD, DRASTIC and SI approaches have been the most extensively tested. This is why, in the present work, we applied them to evaluate the groundwater vulnerability of the Ghiss-Nekkour aquifer, located in North East of Morocco, on its Mediterranean shore. The mapping resulting from the application of the three approaches shows a range of intervals divided into classes corresponding to fluctuating degrees of vulnerability from “very low” to “extreme”. The coincidence rate between the nitrate distribution of the groundwater and the mapped vulnerability classes is higher when the SI approach is applied. Such mapping constitutes basic documents guiding the land planner in decision-making within a framework of territorial intelligence and integrated management of the Ghiss-Nekkour coastal basin.
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