Statistical approach of factors controlling drainage network patterns in arid areas. Application to the Eastern Anti Atlas (Morocco)

International audience12 13 Abstract: 14 Several studies have revealed that the complexity in the distribution of drainage network patterns is not 15 random and controlled by major parameters, variable in space but also throughout geological time. Drainage 16 networks in the Eastern Anti-Atlas of Morocco consist of complex spatial arrangements with various types of 17 patterns, such as trellis, angular, dendritic and parallel. The objective was to distinguish, quantify and rank 18 the relationship that may exist between the different drainage networks patterns, geology and 19 geomorphology. A total of 230 basins were extracted from the ASTER-GDEM Elevation Data (USGS), which 20 were assigned 16 parameters reflecting their topography, morphometry, slope and geology. The statistical 21 treatment of the dataset (16 variables x 230 observations) was carried out through principal component 22 analysis (PCA), linear discriminant analysis (LDA) and agglomerative hierarchical clustering (AHC), in order to 23 investigate the complexity of drainage network patterns and their distribution. The PCA showed that the 24 topographical, slope and geological parameters, i.e. primarily the parameter associated with structural 25 control, best explains the variation in the type of the drainage pattern. The LDA made it possible to distinguish 26 between the four types of drainage patterns with a success rate of 90%, using 3 discriminant functions that 27 were better correlated with geological and slope parameters. LDA and AHC statistical treatments show 28 confusion between the parallel, trellis and angular patterns, on the one hand, due to similar factors 29 responsible for their formation, and on the other because of transitions phenomenon from one drainage 30 pattern to another over time or space. Such possible drainage network shifting may be explained by the 31 geological events that have occurred in the Eastern Anti Atlas from Lower Mesozoic to the Quaternary. 32 3

Mapping the pollution plume using the self-potential geophysical method: case of Oum Azza Landfill, Rabat, Morocco

The main landfill in the city of Rabat (Morocco) is based on sandy material containing the shallow Mio-Pliocene aquifer. The presence of a pollution plume is likely, but its extent is not known. Measurements of spontaneous potential (SP) from the soil surface were cross-referenced with direct measurements of the water table and leachates (pH, redox potential, electrical conductivity) according to the available accesses, as well as with an analysis of the landscape and the water table flows. With a few precautions during data acquisition on this resistive terrain, the results made it possible to separate the electrokinetic (~30%) and electrochemical (~70%) components responsible for the range of potentials observed (70 mV). The plume is detected in the hydrogeological downstream of the discharge, but is captured by the natural drainage network and does not extend further under the hills.info:eu-repo/semantics/publishedVersio

Evaluation of the acceptability of improved supplementary foods for the treatment of moderate acute malnutrition in Burkina Faso using a mixed method approach.

The objective of this study was to evaluate, within the context of a randomized controlled trial of product effectiveness, the acceptability of new formulations of six corn-soy blended flours (CSB) and six lipid-based nutrient supplements (LNS) with different quantities of milk and qualities of soy for the treatment of children with moderate acute malnutrition (MAM). Our study included 1546 children aged 6-23 months and involved questionnaires after one month of supplementation home visits and interviews with a sub-sample of 20 trial participants and their caretakers, and nine focus group discussion. All 12 products were well accepted in terms of organoleptic qualities and received good ratings. However, LNS were more appreciated by caretakers and children. Additionally, an effect of soy isolate was detected on child appreciation where products with high milk content also received better ratings. CSB were not consumed as readily; 33.9% (n = 257) of children receiving CSB were reported to have leftovers compared to 17.3% (n = 134) of children receiving LNS (p=<0.001). Both CSB and LNS were referred to as foods with medicinal properties and perceived as beneficial to child health. They were both reported to have high priority in the daily feeding of the child. In conclusion, there were minimal differences in acceptability of the various CSB and LNS formulations, although CSB were less readily consumed and required smaller meal volumes. Since all products were well-accepted, decisions regarding whether the more expensive products should be used for the treatment of MAM will need to be based on their effect on child nutrition, growth and health. Future supplementary feeding programs in similar contexts could furthermore consider introducing supplementary foods as a medical treatment, as this may increase adherence and decrease sharing

Early development in children with moderate acute malnutrition: A cross-sectional study in Burkina Faso

Malnutrition impairs cognitive, communication, and motor development, but it is not known how nutrition and health are associated with development in children with moderate acute malnutrition (MAM). We aimed to describe motor and language development of children with MAM and explore its nutrition and health-related correlates. This cross-sectional study used baseline data from a nutritional trial in children with MAM aged 6-23 months in Burkina Faso. Motor and language skills were assessed using the Malawi Development Assessment Tool (MDAT). Linear mixed models were used to explore potential correlates of MDAT including socio-economic status, anthropometry, body composition, whole-blood polyunsaturated fatty acids (PUFA), haemoglobin (Hb), iron status, and morbidity. We also assessed child and caregiver participation during MDAT procedures and their associations with correlates and development. MDAT data were available for 1.608 children. Mean (95% CI) MDAT z-scores were -0.39 (-0.45, -0.34) for gross motor, 0.54 (0.48, 0.59) for fine motor, and -0.91 (-0.96, -0.86) for language skills. Children with higher mid-upper arm circumference, weight-for-height, height-for-age, fat-free mass, n-3 PUFAs, Hb, and iron status had better MDAT z-scores, whereas children with more fat mass index, anaemia, illness, and inflammation had poorer z-scores. In addition, children living in larger households or with an unmarried mother had poorer MDAT z-scores. Associations between morbidity and z-scores were largely explained by children's poorer participation during MDAT assessment. The identified factors associated with child development may inform interventions needed to stimulate development during or after management of MAM

Ressources en eau souterraine du centre urbain de Ouagadougou au Burkina Faso, qualité et vulnérabilité

La croissance démographique de Ouagadougou la capitale du Furkina Faso entraîne une pénurie d'eau dans les zones périphériques de la ville qui sont confrontées aux problèmes d'alimentation en eau, en quantité et surtout en qualité. Cette étude a pour but de faire un état de la ressource en eau souterraine et de sa vulnérabilité. Ouagadougou est bâtie au centre du Pays, entre 280 m et 300 m d'altitude sur des formations de socle cristallin et cristallophyllien du paléo protérozoïque. Ces formations sont recoupées par des intrusions et de grandes fractures orientées Nord-Sud et Est-Ouest. Le tout est recouvert par une épaisse couverture d'altérites. On y distingue trois niveaux plus ou moins aquifères mais généralement deux nappes : celle supérieure avec la cuirasse quand elle est noyée, captée par des puits et l'autre inférieure regroupant les arènes et la roche fissurée-fracturée, captée par les forages. Les paramètres hydrodynamiques des aquifères inférieurs de fissures sont très intéressants grâce aux fractures qui constituent dans cet environnement de socle les voies privilégiées d'accès aux ressources en eau mais aussi et d'arrivée de polluants. Les outils hydrogéochimiques permettent de comprendre la complexité des aquifères de socle de Ouagadougou, leur fonctionnement et d'identifier la pollution au niveau des eaux des puits qui voient leur conductivité augmenter avec l'alcalinité (bicarbonates) par suite de minéralisation de la matière organique des charges anthropiques. Une cartographie des nitrates sur 1800 puits répertoriés à Ouagadougou basée sur une approche géostatistique par analyse variographique met en évidence trois grandes zones avec des concentrations excessives des nitrates allant parfois jusqu'à 150 mg/l. La dégradation de la qualité des eaux qui s'accompagne de la présence de coliformes et streptocoques fécaux est due à l'environnement immédiat de ces ouvrages côtoyant couramment latrines et eaux usées. L'essai de cartographie de la vulnérabilité de la nappe inférieure a été effectué à partir de deux paramètres : la densité de fracturation et l'épaisseur des altérites. Cette première ébauche indique deux zones très vulnérables sur lesquelles une grande attention doit être portée à l'occupation des sols et l'assainissementThe growth of Ouagadougou population, in the capital of Burkina-Faso (with more than 1 million inhabitants) results in drinking water shortage in peripheral areas of the city (Ouagadougou) which are confronted to drinking water problems in quality and mainly in quantity. This study aims the investigation of groundwater situation and the appreciation of its quality and its vulnerability. Ouagadougou is situated in the centre of Burkina-Faso, to an altitude comprised between 280 m and 300 m, laid on paleo proterozoic crystalline and foliated crystalline bedrock formations with cut by intrusions and high fractures oriented South North and East West. All is covered by thick weathered zone. One distinguishes in these formations more than less three aquifer levels but generally two groundwater table : the superficial water table captured of laterite when it is drowned, and the deep aquifer comprising granitic sand and fractured bedrock captured of boreholes. Hydrodynamic parameters of fractures water table are very interested because of the fractures which are in this bedrock environment the main access road to water resources but also and mainly the arrival road of pollutants. Hydrogeochemical tools enable to understand Ouagadougou bedrock aquifers complexity and to show the important pollution in water wells which have seen their conductivity increase with alkalinity (bicarbonate) mainly due to the mineralization of organic matter from anthropogenic charges. Nitrate cartography on 1800 wells indexed in Ouagadougou based on geostatistic approach by variogram analysis show three zones with nitrate excessive concentrate values approaching 150 mg/l. Water quality degradation accompanied by faecal streptococcus and coli forms presence is due to wells proximity from latrines and waste water. The vulnerability cartography test was carried according to two parameters : fracture density and weathered zone thickness. This first approach shows two most vulnerable zones on which a great attention must be paid for sol occupation and hydraulic urbanAVIGNON-BU Centrale (840072102) / SudocSudocFranceF

Caractérisation du fonctionnement des aquifères de socle dans la région de Ouagadougou à partir d’une étude de la qualité chimique des eaux

Une partie de l’alimentation en eau potable de Ouagadougou provient d’environ 1 800 puits traditionnels et 100 forages plus profonds de 40 à 65 m en moyenne. Une étude hydrochimique a été menée pour mieux connaître la qualité de la ressource en eau captée. Ses résultats permettent de proposer un modèle conceptuel du fonctionnement des aquifères dans la région de Ouagadougou, en contexte de socle cristallin.La ville connaît un climat de type soudano-sahélien avec une saison des pluies de juin à septembre et une saison sèche d’octobre à mai. Les précipitations moyennes sont de l’ordre de 700 mm. La géologie du secteur d’étude est constituée de formations de socle cristallin comportant une épaisse couverture d’altérites de 30 m environ. On y distingue, d’une part, l’aquifère supérieur libre de la cuirasse latéritique, capté par les puits et, d’autre part, isolé à son toit par des altérites argileuses, l’aquifère inférieur, souvent captif, constitué par les arènes grenues et le socle cristallin fissuré ou fracturé sous-jacent. Ce second aquifère est capté par les forages.L’eau des forages profonds présente un faciès bicarbonaté calcique et magnésien alors que celle captée par les puits présente un faciès chloruré et nitraté à tendance sodique. Le processus dominant dans l’aquifère inférieur est l’hydrolyse des silicates, alors que l’aquifère supérieur est fortement influencé par des apports superficiels. Dans ce cas, la minéralisation de la matière organique anthropique favorise la dissolution des silicates. Deux paramètres facilement mesurables sur le terrain, la conductivité électrique et l’alcalinité de l’eau, permettent de juger de ce phénomène.Les teneurs en nitrates dépassent les normes de l’OMS dans près de 60 % des 1 800 puits répertoriés. Le traitement statistique des concentrations mesurées en fonction de la distance séparant les différents ouvrages met en évidence l’hétérogénéité du milieu et le caractère localisé de l’influence des apports anthropiques. Cela confirme le concept d’une hydrodynamique en milieu discontinu caractéristique des zones de socle. Les variations saisonnières des teneurs en nitrates dans les puits indiquent un phénomène de pluvio-lessivage des sols durant la saison humide. Les teneurs en isotopes stables de l’eau (18O/2H) permettent de distinguer les puits, marqués par des phénomènes d’évaporation, des forages, dont les teneurs sont proches des teneurs moyennes pluriannuelles des pluies de pleine mousson. Ces observations valident un processus de recharge hétérogène et sélective. Elles indiquent deux types de recharge : l’une s’effectue directement à travers le manteau d’altération et l’autre de manière retardée à partir de mares et marigots soumis à des phénomènes d’évaporation.Some 1800 traditional wells and 100 deep boreholes (40 to 65 m depth) contribute to the drinking water supply of Ouagadougou. In order to better know the origin of the mineralization, the concentration trends and to characterize the structure and the functioning of the aquifers, a hydrochemical study has been carried out. The city is located in the Sudano-Sahelian climate zone with a rainy season from June to September and a dry season occurring between October and May. The average rainfall is about 700 mm. The geology of the study area comprises crystalline formations overlain by a layer of weathered materials about 30 m thick. Hydrogeologically, two main aquifers are encountered here: the near surface aquifer located in the laterites and exploited through hand-dug wells, and the deep aquifer consisting of coarse sands and fractured bedrock. The latter aquifer, most of the time confined, is tapped by the boreholes and is isolated from the first by clayey formations.Regarding the chemistry, water from the boreholes shows a bicarbonate calcic and magnesium facies, whereas the well waters are characterized by a chlorinated and nitrate facies with a sodium trend. The dominant process in the deeper aquifer is the hydrolysis of silicates. The near-surface aquifer is highly influenced by superficial supplies. In this case, the mineralization of the anthropogenic organic matter encourages the dissolution of the silicates. The electrical conductivity and the alkalinity, easily measurable in the field, support this suggestion. The nitrate contents exceed WHO norms in nearly 60% of the 1800 inventoried wells. Their statistical analysis in relation to the distances between the different sampling points highlights the heterogeneity of the environment and the localized state of the influence of the anthropogenic supplies, confirming the hydrodynamic concept of a discontinuous environment typical of bedrock zones. The seasonal variations of nitrate concentrations in the wells reflect soil leaching phenomena during the wet season.The stable isotope (18O/2H) content of the waters allowed a differentiation between the wells characterized by evaporation processes and the boreholes showing contents close to multi-year mean values of the monsoon rainfalls. These observations suggest two types of recharge: the first type takes place directly through the weathered mantle and the second type, delayed, occurs through lakes and creeks under evaporation conditions

Groundwater level changes since 1978 in an African city on basement rocks : the case of the CIEH borehole in Ouagadougou (Burkina Faso)

International audienceThe CIEH piezometer, located in the center of Ouagadougou city presents a water level record spanning the West African Drought which peaked during the 80s and 90s. Its water level is investigated as a potential proxy for groundwater water resources in West African basement rock aquifers submitted to climate changes. 23 boreholes and wells in various land uses and within a 2 km radius around the CIEH piezometer were monitored during the 2013-2014 hydrologic year. The minimum water level occurred in May, at the end of the dry season, while the maximum took place in October, one month after the end of the rainy season. The mean water level amplitude is 3 m, the minimum amplitude being reached at the CIEH piezometer (0.76 m). Moreover, the CIEH piezometer is located in a 2 m amplitude water table depression either in May or in October. Simplified 2d modeling using a general basement aqui-fer structure shows that (i) the water level in the piezometer is under ongoing influence of the spillway raise of the nearby dam#3 lake in 2002, (ii) the whole 1978-2004 period cannot be modelled with constant parameters. A 3% decrease of water uptake is adopted after 1985, presumably resulting from land use changes in the Ouagadougou city. The water table at the CIEH piezometer is presently at its 1978 level, which can considered as a pre-drought value. However this includes a 1.5 m contribution of the two abovementioned anth-ropic effects Further quantitative interpretations of the CIEH piezometer record will require additional geophysical and hydrological investigations

The impact of the Oum Azza landfill on the quality of groundwater at the Rabat region (Morocco)

A 110 ha dump, located in the Akrach shallow aquifer area in Morocco, was studied in order to characterize the quality of groundwater around the landfill, to delineate the contaminated area and to determine the factors favouring the contamination of groundwater. This dump is located in the city of Oum Azza (15 km south from Rabat), (Map 1). between the Akrach River in the west and the Sidi Mohamed Ben Abdellah Dam in the east. To assess groundwater pollution from this landfill, piezometric monitoring and Hydrochemical analyses were conducted on 22 wells. The results highlight a significant degradation in the groundwater quality, especially in the parts located in the direct vicinity downstream the dump. In the impacted areas, electrical conductivity was above 1100 μS cm-1, bicarbonates were higher than 508 mg L-1, chlorides, sulphate, and nitrates contents were higher than 850, 200 and 1 mg L-1, respectively. In addition we found high cadmium (50 - 100 μg L-1) and chromium (40 - 230 μg L-1) contents, i.e. much higher than the WHO guidelines for drinking or irrigation water. A principal component analysis conducted on this dataset highlights the absence of a prevalent principal component (PC), with the variance distributed across many PCs. The mechanisms responsible for the chemical variance of the hydro system are therefore numerous and fairly balanced in terms of influence. Finally, a hierarchical classification brings out three groups of observations, each group corresponding to a level of pollution.The impact of the Oum Azza landfill on the quality of groundwater at the Rabat region (Morocco) L’impact de la decharge d’Oum Azza sur la qualite des eaux souterain region de Rabat (Maroc) La décharge étudiée est localisée dans la zone de l’aquifère peu profond d’Akrach (Map 1). Elle est d’une superficie de 110 ha, située sur la commune d’Oum Azza à 15 Km de Rabat, entre la rivière Akrach à l’ouest et le barrage de Sidi Mohamed Ben Abdellah à l’est. Le but de cette étude est de caractériser la qualité des eaux souterraines autour de la décharge, de délimiter la zone contaminée et de déterminer les facteurs favorisant la contamination des eaux souterraines. Pour évaluer la pollution des eaux souterraines due à cette décharge, des analyses de niveau piézométrique et Hydrochimique ont été réalisées sur 22 puits. Les résultats des analyses géochimiques montrent une dégradation qualitative importante des eaux souterraines, en particulier dans les parties situées dans la zone de gradient descendant et à proximité directe de la décharge. Dans ces zones polluées, nous avons observé les valeurs suivantes: supérieure à 1100 μS/cm en conductivité électrique, 508mg/L en bicarbonates, 850mg/L et 200mg/L respectivement en chlorures et sulfate, 1mg/L en nitrates, 50 - 100 mg/L en cadmium, et 40 - 230 μg/L en chrome. Ces concentrations dépassent largement les valeurs standards de l’Organisation Mondiale de la Santé (OMS) pour l’eau potable et l’eau d’irrigation. Une analyse en composantes principales réalisée sur cet ensemble de données met en évidence l’absence d’une composante principale (PC) prévalente, la variance étant répartie sur de nombreux PC. Les mécanismes responsables de la variance chimique d’hydro système sont donc nombreux et assez équilibrés en termes d’influence. Enfin, une classification hiérarchique fait apparaître trois groupes d’observations, chaque groupe correspondant à un niveau de pollution.Un vertedero de 110 ha, ubicado sobre el acuífero superficial de Akrach en Marruecos, ha sido estudiado para caracterizar la calidad de las aguas subterráneas alrededor del vertedero, conocer la extensión del área contaminada y estudiar los factores involucrados en esta contaminación. El vertedero se emplazó en la ciudad de Um Azza (15 km al sur de Rabat), entre el rio Akrach, al oeste, y la represa Sidi Mohaed Ben Abdallah, al este. Un control piezómetro y análisis químicos se hicieron sobre 22 pozos para estudiar esta contaminación. La calidad del agua es afectada por una contaminación importante, especialmente en las áreas al contacto cercano del vertedero, y aguas abajo de este mismo. En las zonas afectadas la conductividad eléctrica de las aguas supera 1100 µS.cm-1, los bicarbonatos superan 508 mg.L-1 , los cloruros, sulfatos y nitratos superan 850,200 y 1 mg.L-1. Además se consiguió alto contenido en cadmio (50-100 µg.L-1) y cromo (40- 230 µg.L-1). En definitiva, se superaron olgadamente los valores estipulados en las normas de la OMS para el agua potable y de riego. Un análisis en componentes principales se llevó a cabo sobre el conjunto de datos. No aparece un eje factorial consistente, sino más bien muchos ejes de importancia similar, lo que muestra un conjunto de mecanismos de la misma fuerza involucrados en la calidad química de las aguas contaminadas. Una clasificación jerárquica ascendente da tres grupos de muestras, cada grupo corresponde a un nivel de contaminación

L'impact de la décharge d'Oum Azza sur la qualité des eaux souterraines au niveau de la région de Rabat (Maroc)

International audienceA 110 ha dump, located in the Akrach shallow aquifer area in Morocco, was studied in order to characterize the quality of groundwater around the landfill, to delineate the contaminated area and to determine the factors favouring the contamination of groundwater. This dump is located in the city of Oum Azza (15 km south from Rabat), (Map 1). between the Akrach River in the west and the Sidi Mohamed Ben Abdellah Dam in the east. To assess groundwater pollution from this landfill, piezometric monitoring and Hydrochemical analyses were conducted on 22 wells. The results highlight a significant degradation in the groundwater quality, especially in the parts located in the direct vicinity downstream the dump. In the impacted areas, electrical conductivity was above 1100 μS cm-1, bicarbonates were higher than 508 mg L-1, chlorides, sulphate, and nitrates contents were higher than 850, 200 and 1 mg L-1, respectively. In addition we found high cadmium (50 - 100 μg L-1) and chromium (40 - 230 μg L-1) contents, i.e. much higher than the WHO guidelines for drinking or irrigation water. A principal component analysis conducted on this dataset highlights the absence of a prevalent principal component (PC), with the variance distributed across many PCs. The mechanisms responsible for the chemical variance of the hydro system are therefore numerous and fairly balanced in terms of influence. Finally, a hierarchical classification brings out three groups of observations, each group corresponding to a level of pollution.Un vertedero de 110 ha, ubicado sobre el acuífero superficial de Akrach en Marruecos, ha sido estudiado para caracterizar a la calidad de las aguas subterráneas al rededor del vertedero, de conocer la extensión del área contaminada y estudiar a los factores involucrados en esta contaminación. El vertedero se ubicado en la ciudad de Um Azza (15 km al sur de Rabat) (mapa 1), entre el rio Akrach al oeste y la represa Sidi Mohaed Ben Abdallah al este. Un control piezómetro y análisis químicos se hicieron sobre 22 pozos para estudiar esta contaminación. La calidad del agua es afectada por una contaminación importante especialmente en las áreas al contacto cercano del vertedero y aguas abajo de este mismo. En las zonas afectadas la conductividad eléctrica de las aguas supera 1100 µS.cm-1 , los bicarbonatos superan 508 mg.L-1 , los cloruros, sulfatos y nitratos superan 850,200 y 1 mg.L-1. Además se consiguió alto contenido en cadmio (50-100 µg.L-1) y cromo (40-230 µg.L-1) o sea mucho más que las normas de la OMS para el agua para beber o regar. Un análisis en componentes principales e llevo a cabo sobre el conjunto de datos. No aparece un eje factorial fuerte sino más bien muchos ejes de semejante fuerza, lo que muestra un conjunto de mecanismos de misma fuerza involucrados en la calidad química de las aguas contaminadas. Una clasificación jerárquica ascendente da tres grupos de muestras, cada grupo corresponde a un nivel de contaminación

Hydrochemical characterisation of groundwater using multifactorial approach in Foum el Gueiss basin, Northeastern Algeria

Knowledge of the quantity and quality of groundwater is a prerequisite to encourage investment in the development of a region and to consider the sedentarisation of populations. This work synthesises and analyses data concerning the chemical quality of the available water acquired in the Foum el Gueiss catchment area in the Aures massif. Two families of waters are observed, on the one hand, calcium and magnesian chlorated-sulphate waters and on the other hand, calcium and magnesium bicarbonate waters. Multivariate statistical treatments (Principal Component Analysis – PCA and Discriminant Analysis – DA) highlight a gradient of minerality of the waters from upstream to downstream, mainly attributed to the impact of climate, and pollution of agricultural origin rather localised in the lower zones. These differences in chemical composition make it possible to differentiate spring, well and borehole waters. The main confusion is between wells and boreholes, which is understandable because they are adjacent groundwater, rather in the lower part of the catchment area. The confusion matrix on the dataset shows a complete discrimination with a 100% success rate. There is a real difference between spring water and other samples, while the difference between wells and boreholes is smaller. The confusion matrix for the cross-validation (50%)