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Message des coprésidents de La Revue des Sciences de l’Eau (RSE) sur la Fin de la publication

Jean-Pierre Villeneuve and Nicolas Roche

Évaluation de la vulnérabilité à la pollution des eaux souterraines par la méthode DRASTIC : cas de la nappe alluviale de Rich (Haut Atlas central, Maroc)

Youssef El Kayssi, Mohamed Hilali, Taoufiq Kouz and Ilias Kacimi
Rapid urbanization and corresponding wastewater discharges and the increasing use of chemical fertilizers in agriculture are a potential risk for groundwater pollution. Mapping the vulnerability of groundwater to pollution minimizes this risk by identifying the most sensitive areas to help a good qualitative management of the resource. Here, the vulnerability was assessed using the DRASTIC method, in comparison with PRK method (where P is the topographic slope, R the ratio of the piezometric level fluctuations to the thickness of the unsaturated zone, and K the aquifer permeability) for the Rich alluvial aquifer (Central High Atlas of Morocco). The vulnerability map obtained was tested and validated with the electrical conductivity of 44 wells using the Kappa test and the coincidence rate. The result obtained showed a low K (0.006) and a low coincidence rate of 24%, which validated partly the obtained vulnerability map. The vulnerability classes obtained showed that 21.7% of the study area had low to very low vulnerability, 56.6% moderate vulnerability, and 21.7% high to very high vulnerability. The complexity in producing this vulnerability map comes from the choice of the parameter to reflect the state of the pollution, and also in the density of the input data and how it is introduced, often by interpolation, assigning values in sectors where no data is known or exists. Finally, an update of this vulnerability map becomes necessary by choosing a different pollution indicator or by using a greater amount of data in the model in order to have a more reliable result to be used to raise awareness of the public services concerned by groundwater in the area.

Variabilité pluviométrique dans le bassin versant du Haut et Moyen Cheliff

Sekina Amiar, Abderrazak Bouanani, Kamila Baba-Hamed and Halima Belarbi
Algeria, an arid to semi-arid country, is highly vulnerable to climate change. Rainfall is limited in the coastal zone, uncertain or even non-existent towards the South, and is particularly vulnerable to the negative effects of global warming. There is a downward trend in rainfall since 1975 and the rising phase is not yet ready to begin.The purpose of this work is to analyze the interannual variability of the rainfall time series of 17 stations in the Upper and Middle Cheliff watershed over the period 1972/73-2012/13 (42 years). The seven-year moving average method and non parametric statistical tests (Pettitt and Mann-Kendall) have been used to analyze these time series. This analysis shows the existence of a succession of wet (1972/73 to 1979/80) and dry (1979/80 to 2005/06) sequences common to 14 stations. The rupture date detected for the majority of the stations is between the end of the 1970s and the middle of the 1980s. Indeed, 6 stations out of 17 have a regular rainfall pattern, while the remaining 11 stations have a rainfall deficit that fluctuates between 16% and 29%.

Biochars issus de roseau commun pour l’adsorption du méthylorange en solution aqueuse / Common reed biochars for the adsorption of methyl orange in aqueous solution

Soriya Melouki, Abdelbaki Reffas, Abdellah Merrouche, Laurence Reinert and Laurent Duclaux
The textile industry uses large amount of water and organic dyes to tint their products. These synthetic dyes are toxic and cause water coloring. This results in colored wastewater that must be treated before being discharged. In addition, most dyes are not biodegradable, and once released they alter the aquatic environment. Among the processes for treating these effluents, adsorption is an easy and a cost-effective process to implement. The objective of this study is the preparation of biochars from common reed applicable for the discoloration of effluents used in the textile industry. Common reed (Phragmites australis) has been collected from the Sed-Ksob river of M'sila (Algeria) and used as precursor for the production of biochars activated by phosphoric acid. The surface chemistry of the prepared materials has been characterized using selective titration (Boehm assay), TGA analysis and pH of point zero charge (pHpzc) measurements. The porous texture has been investigated by using methylene blue adsorption and iodine number measurements. The results of the TGA analysis and the Boehm assay show the presence of many superficial functional groups on the surface of the biochars. The amount of oxygenated functional groups on all the prepared biochars depends on the impregnation ratio of phosphoric acid, except for the one obtained at 150% impregnation ratio. The adsorption of methylene blue and the iodine test indicate an increase in the specific surface area with an increase in the impregnation ratio due to the development of the microporosity and the mesoporosity. The adsorption properties of methyl orange, an anionic dye, were studied on the prepared biochars as function of concentration, contact time, and temperature. The Langmuir model describes well the equilibrium adsorption of methyl orange on the prepared biochars. The adsorption kinetics are described by the pseudo-second order and the liquid film diffusion models. An endothermic physical adsorption of methyl orange on the prepared biochars has been highlighted.

Déterminants des volumes d’eau potable utilisés en milieu rural dans la basse vallée de l’Ouémé au Bénin

Fêmi Cocker, Jean-Bosco Kpatindé Vodounou and Jacob Afouda Yabi
This study aims to characterize the quantity of drinking water taken by households in the Lower Oueme Valley in Benin. To identify the determinants of the quantity of water used, simple and multiple logistic regressions were performed using SPSS 23 and XLSTAT software. Data included in this study were collected in 175 households. The results reveal that the quantity of drinking water used in the Lower Oueme Valley for domestic needs is 34 ± 12 L∙d-1 per inhabitant. However, this amount of water varies, depending on the geographical setting and factors such as the availability of drinking water sources, the distance to the source, and the season. Thus, the quantity of water used in the communes of Adjohoun (39 ± 14 L∙d-1 per inhabitant) and Dangbo (36 ± 12 L∙d-1 per inhabitant) is greater than the average of the study, while those of Bonou (34 ± 12 L∙d-1 per inhabitant), Sô-Ava (32 ± 12 L∙d-1 per inhabitant) and Aguegues (27 ± 10 L∙d-1 per inhabitant) are below the average. The non-availability of drinking water sources (adjusted odds ratio [AOR] = 0.05 [0.01-0.29], p < 0.01), the rainy season (AOR = 0.17 [0.04-0.76], p < 0.05) as well as distances greater than 300 m (AOR = 0.13 [0.02-0.7], p < 0.05) predict a risk of water comsumption of less than 20 L∙d-1 per inhabitant.

Chezy’s resistance coefficient in a horseshoe-shaped tunnel

Imed Loukam, Bachir Achour and Messaoud Djeddou
The calculation of Chezy’s resistance coefficient (CRC) is typically not provided a priori in a design problem, and its value is often selected subjectively from the literature in most open channels and conduits for the uniform flow. The evaluation of this coefficient is crucial to channel design and for computing its normal depth. The primary purpose of this research study is to revisit the mathematical formulation for the resistance coefficient. A general explicit relation of the resistance coefficient in turbulent flow is set with different geometric profiles of conduits and channels, mainly the horseshoe-shaped tunnel using the rough model method (RMM). CRC is firmly based on the internal walls' absolute roughness of the channel, the liquid kinematic viscosity, the longitudinal slope, the discharge and the filling rate. Additionally, a simplified method is proposed to determine CRC with a restricted number of variables such as the kinematic viscosity, the absolute roughness, the slope of the conduit, and the discharge. Based on studying the variation of CRC as a function of the filling rate, another explicit expression is provided to compute this coefficient efficiently when its maximum value is reached. To demonstrate how Chezy’s resistance coefficient can be calculated in a horseshoe-shaped tunnel, some examples of calculations are proposed.

Regards croisés sur l’évolution de la pénurie d’eau de la ville de Zinder (Niger) de 1900 à nos jours

Moussa Malam Abdou, Boubé Bali Saley, Ibrahim Mamadou and Laminou Issaka Brah
The town of Zinder has been confronted to a recurring drinking water scarcity since the 1920’s. The causes of this problem are diversely interpreted according to the contexts and periods. This paper proposes a critical look at this situation for a better understanding of the problem. From an inventory of etiological narratives analyzed with the tools of the myth critique, on the one hand, hydrometric data and surveys, on the other hand, questions relating to the production and management of water, as well as people’s pessimism as to a definitive solution to this problem are studied. Cross-analyses highlight three main explanations of the issue of water in Zinder. The popular imagination teaches that the lack of water finds its explanation in myths, which far from being mere cultural ornaments, are part of a perspective of legitimizing African people’s power against the white-skinned invaders. In addition, drilling flow analysis reveals there is a low availability of water resource due to the crystalline subsoil, which has been very little altered. Thus, of the fifteen or so water drilling points sampled around the city, the average productivity is 0.57 m3∙h-1 (±0.47). Sixty percent of water drilling points have below the average flow; therefore, they are barely considered as productive. Finally, the volumes of water produced by pumping stations are always lower than the increasing needs of the population. To manage the shortage, the city’s water management services have developed strategies such as the use of water access voucher, the limitation of connections and selective water cut. Despite the building of hydraulic infrastructures and the scientific arguments, the populations are less and less convinced about the definitive resolution of this problem due to the persistence of the shortage. Therefore, depending on the informants and the spatial scale of analysis, the shortage can be explained as a natural, economic, and socio-political issue.

Évaluation de la pollution azotée minérale des eaux superficielles de la zone humide Ramsar du lac Fetzara (Nord-Est algérien)

Khaoula Boulaksaa and Aziz Laifa
By its size and specificity, the Ramsar wetland of Lake Fetzara is representative of the rare type of natural wetland in the Mediterranean region. The agropastoral activity practiced in its peripheral zone and the wastewater of the surrounding urban agglomerations constitute potential sources of pollution of the lake waters by nutritive elements. This study was conducted with the objective of assessing the pollution of surface waters of the Fetzara Lake wetland by mineral nitrogen. By a spatio-temporal physicochemical approach, the analytical results obtained show that the wetland waters are not polluted by the nitrate ion, whereas the majority of these waters are rich in nitrite ions. The agricultural activity that characterizes this area would be the direct or indirect source of this pollution. With regard to ammonium ion contamination, all the stations studied have net pollution with maximum values (up to 20.7 mg∙L-1) in stations receiving urban wastewater. The mineral nitrogen concentrations become considerably high during the year 2016 and vary spatially depending on the distance from the source of pollution and with respect to the wet and dry seasons.

Variation de l’abondance des nauplii de copépodes et influence des variables environnementales sur leur développement dans les eaux du Haut-Bandama (Côte d’Ivoire)

Tiéligounon Ali Soro, Raphaël N’doua Etilé and Gouli Gooré Bi
The aim of this study is to investigate spatial and temporal variations of copepod nauplii abundance in relation to environmental factors. To this end, water and zooplankton sampling was conducted from November 2017 to September 2018 in the Lokpoho River (tributary of the Bandama River) and in the main stem of the Bandama River. The analyses of the samples showed that copepod nauplii are more abundant in the dry season (mean 74 ind∙L-1) than in the rainy season (mean 51 ind∙L-1), with the highest values recorded in the middle of the dry season (118 ind∙L-1). The average annual abundance of nauplii in the Lokpoho River (77 ind∙L-1) is higher than in the Bandama River (38 ind∙L-1). During the dry season, nauplii abundance is strongly influenced by conductivity, dissolved oxygen and pH. During the rainy season, the main variables influencing nauplii abundance are manganese, transparency, chlorophyll a and nitrate. Annually, the abundance of copepod nauplii is positively and significantly influenced by the abundance of adult copepods and transparency. However, nitrate levels have a negative influence on the development of copepod nauplii in the Upper Bandama. This negative influence is thought to be due to agro-pastoral activities in the Ferké region.

Assessment of the water quality of the upper reaches of the ouémé river in benin using benthic macroinvertebrate-based biotic indices

Koudjodé Simon Abahi, Modeste Fadéby Gouissi, Hotèkpo Hervé Akodogbo, Sorébou Hilaire Sanni Worogo, Ayodélé Shola David Darius Adje and Pierre Midogbo Gnohossou
To cope with the numerous consequences of stream pollution caused by anthropogenic activities, it is necessary to evaluate the water quality for sustainable management. The present study aims to evaluate the water quality of the upper reaches of the Ouémé River in Benin using biotic indices based on benthic macroinvertebrates. Macroinvertebrates were sampled using a Surber net in four stations distributed over the longitudinal profile of the upper reaches of the Ouémé River. After sample collection, the macroinvertebrates were separated, identified and counted under a stereo-microscope. A total of 13 macroinvertebrate orders and 24 macroinvertebrate families were collected in this study. The Chironomidae was the most abundant family. The results of the Ephemeroptera, Plecoptera, Trichoptera (EPT) Index, the EPT/Chironomidae Index, the Hilsenhoff Index and the Standardized Global Biological Index (IBGN) revealed that the Upper Ouémé River has very poor water quality. The intense pressures from human activities in this part of the river have led to serious organic pollution, which has resulted in the proliferation of macroinvertebrates resistant to pollution to the detriment of those sensitive to pollution. On the basis of this result, protection and recovery measures must be taken to preserve and improve the ecological status of the waters of the upper reaches of the Ouémé River.

Étude des biofilms bactériens isolés à partir du système de distribution d’eau potable dans la région sud-est de l’Algérie

Amina Lamache, Ibtissem Doghri, Mario Jacques and Saliha Boudjenah-Haroun
This study attempted to determine the influence of the characteristics of drilling sources and materials used in drinking water distribution systems on the development of biofilms in pipe networks in southeastern of Algeria (Ouargla). Our samples were selected according to the aquifer, pipe material and age in this region. To carry out our experiments, we mechanically took 27 biofilm samples from several distribution pipes based on different types of materials: copper, polyvinyl chloride (PVC) and high-density polyethylene (HDPE), and from different aquifers (Albian, Senonian and Miopliocene). Several bacterial strains have been identified using the Matrix-Assisted Laser Desorption/Ionization-Time of Flight Mass Spectrometry (MALDI-TOF) technology. The results obtained demonstrate that copper pipes appear to be unfavorable to bacterial colonization while a wide variety of bacterial species has been found on PVC and HDPE materials. The capacity of the isolated strains to form biofilms has also been studied in vitro. The majority of the isolated strains, cultivated in simple and mixed biofilm, showed a strong capacity to form biofilms.

Study of the mobility of trace elements at the water-sediment interface in coastal and estuarine areas

Cheikh Diop and Baghdad Ouddane
In coastal and estuarine environments, trace elements trapped in sediments can be released back into the water column if resuspended during tides or floods. This is how this work is carried out to determine the mobility of trace elements when these phenomena occur on Senegalese coasts subjected to high energy tides. Sequential extraction carried out according to the European Community Bureau of Reference (BCR) was used to determine the mobilizable fraction of trace elements in sediments. Subsequently, laboratory sediment resuspension experiments were conducted to evaluate the ability of sediments to release trace elements into the water in order to better understand the natural effect of resuspension during tidal cycles and water movement on the coast. The release of elements into the water was monitored over a 24 h period along with redox potential (Eh), dissolved oxygen and pH. Bioavailability percentages of Cd, Ni, Pb and Zn showed a strong affinity with the acid soluble fraction, suggesting easy mobility of these elements. The results of the kinetic monitoring tests of the release of trace elements in water show that during the first minutes, desorption is very important with peaks that can reach 90‰ depending on the element that could potentially cause acute effects on aquatic organisms. However, the bioavailability of trace elements in contaminated sediments only influences mobility at the beginning of resuspension. Remobilization tests would therefore provide an indication of the ability of sediments to release trace elements during rapid changes in the physico-chemical conditions of the aquatic environment.