by Eyong Thomson Areakpoh, Akoachere Richard Ayuk II, Omogbemi Omoloju Yaya and Ntonga Jean Claude
Original Research
Aquifers are the main sources of water in Garoua and due to a lack of knowledge of their vulnerability to contaminants for the management and protection of these aquifers, this study to assess their vulnerability to pollution within four hydrogeological seasons using the DRASTIC (Depth-to-water, net-Recharge, Aquifer-media, Soil-media, Topography, Impact-of-vadose-zones and hydraulic-Conductivity) model was a necessity. Depth to water (D) of 196 wells ranged from 0.2 to 11.87 m are assigned ratings of 5, 7, 9 and 10. Net Recharge (R) ranged between 0-35.4 mm/yr. with assigned rating of 1. Aquifer media (A) are alluvium, sandstone, granites, and gneiss with ratings of 10, 8, 10 and 7. Soil media (S) from 50 infiltrometer tests are sands, silty clay, clays and loam soils with assigned ratings of 1, 5, 7 and 10. Topographic (T) slopes from DEMs varied from 0% to 18% were classed into 7 ranges and assigned ratings of 1, 3, 5, 7, 8, 9 and 10. Impact of the vadose zone of sand, clay and gravel were assigned ratings of 3, 9 and 10. Hydraulic conductivity (C) from slug tests on 50 wells ranged from 0.12 to 0.7 m/day and was assigned rating of 1. The derivative DRASTIC scores of aquifer vulnerability to contaminants in Garoua were: 150 in the wet season, 146 in wet-dry season, 158 in dry season and 157 in dry-wet season. DRASTIC indices classified the area into a high vulnerability class in all seasons. These higher vulnerabilities to pollution could be due to porous sandstone formations, the presence of fractured gneisses and fractured granites. From single parameter sensitivity analysis, depth to water, aquifer media, topography and impact of the vadose zone layer tend to be the most effective parameters in the vulnerability assessment because their mean effective weights are higher than their theoretical weights. Highest vulnerabilities to pollution occur during the dry seasons; this is of particular importance since during these periods water is scarce thereby, decreasing the pollution opportunity as there is no transport medium into the aquiferous formations.
American Journal of Water Resources. 2024, 12(1), 12-23. DOI: 10.12691/ajwr-12-1-2
Pub. Date: February 20, 2024
by Issa Malam Salmanou Souleymane, Abdou Babaye Maman Sani, Illias Alhassane and Moussa Issaka Abdoulkader
Original Research
The commune of Gouchi is located in the extreme south of the Zinder Region, resting on a sub-watershed of the Korama, and lies between 13°08' and 13°37' North latitude and 09°26' and 09°47' East longitude (). From a hydrogeological point of view, this zone is essentially underlain by Malawa sandstone and recent sand aquifers. This area, characterized by a high potential groundwater resource and an abundant ecosystem, has been subjected for many years to the phenomena of climate change, land use dynamics and galloping demography. This has resulted in changes to the quantity and quality of the commune's water resources. However, it seems necessary to undertake quantitative and qualitative studies of these groundwater resources, which are the main source of supply for the population, livestock and irrigation. The main objective of the present study is the hydrogeological and qualitative characterization of groundwater in the commune of Gouchi. The methodology adopted can be summed up in three stages: collection and campaign of measurements and samples; laboratory analysis of samples and, finally, processing and statistical analysis of hydrogeological, chemical and bacteriological data, and production of a piezometric map and hydrogeological cross-section. This led to the following results: From a hydrogeological point of view, the depths of the structures, taking into account all the water tables, vary from 2.70 to 49.93 m, with an average of 20.10 m, giving an average depth of 12.85 m. Static levels range from 0.52 m to 28.58 m, with an average of 4.86 m. Water flow rates are highly disparate, ranging from 0.2 to 30 m3/h, with an average of 5.46 m3/h. Furthermore, the piezometric map shows that the direction of groundwater flow is generally from north-west to south-east. This general trend follows the direction of flow of surface water, whose hydrographic network is more or less fossilized (Korama). This suggests that there may be a groundwater-river relationship. As for the chemical results of the 151 water samples, two (02), one hundred and twenty-one (121) and twenty-three (23) were characterized respectively by fluoride, arsenic and nitrate levels exceeding the WHO drinking water standard. Finally, from a bacteriological point of view, of the 151 samples, 56 and 42 showed respectively Total Coliforms (TC) and Escherichia. Coli in groundwater. This could be explained by the lack of hygiene around water points, combined with the shallow depths of the water in places. All these aspects can compromise the population's drinking water supply.
American Journal of Water Resources. 2024, 12(1), 1-11. DOI: 10.12691/ajwr-12-1-1
Pub. Date: January 01, 2024