A regional study connecting geolelectrical surveys with geology and hydrogeology was carried out in the western part of the Iullemmeden basin, precisely in the Dosso region in Niger. One hundred and four (104) vertica...A regional study connecting geolelectrical surveys with geology and hydrogeology was carried out in the western part of the Iullemmeden basin, precisely in the Dosso region in Niger. One hundred and four (104) vertical electrical sounds have been realized, among them nineteen representative were thus be used as parametric surveys. The local resistivity values of the geological formations of Quaternary range from 100 Ω⋅m to 1000 Ω⋅m (sands and lateritic sandstones). The Oligo-Miocene formation of the Continental terminal (Ct) shows resistivity values ranging from 1 to 5 Ω⋅m (brackish groundwaters) to 1500 Ω⋅m (clay sandstones) while the Upper Cretaceous formation of the Continental “hamadien” (Ch) indicates values ranging from 20 Ω⋅m (sandy clay) to 5000 Ω⋅m (clayey sandstones). The geological formations of Paleocene have values from 2 Ω⋅m (marls) to 60 Ω⋅m (calcareous marl), while the Precambrian basement exhibits values of granite around 300 Ω⋅m to 60,000 Ω⋅m. The update of the structural settings reveals many faults in the study area which explain both the shape of the basin and the geometry of the aquifers. Tectonics is also consistent with the hydraulic characteristics of aquifers. In addition, brackish groundwaters were identified as perched aquifer groundwaters in different depths in Dosso region. They probably come from the marine brines during the regression of the Paleocene Sea.展开更多
This study was conducted in the region of Tahoua the northeastern part of the Southern Illulemeden sedimentary basin. In this region the transboundary aquifer system of Continental Intercalaire (CI) and the Continenta...This study was conducted in the region of Tahoua the northeastern part of the Southern Illulemeden sedimentary basin. In this region the transboundary aquifer system of Continental Intercalaire (CI) and the Continental Hamadien (CH) are potentially rich in underground water especially in free and captive aquifers. More, this water is the main source of drinking water for the populations, the animals and for agriculture and extractive industries. However, the population growth, the agricultural development, and the climate change have a real impact on the dynamics of groundwater and the exploitation of these resources. Hence, this study aims at analyzing the behavior of aquifers and assessing the impact of various natural and anthropogenic factors. Especially it matters to analyze the drilling parameters and cuttings, logging data and pumping test of nine new boreholes. The results reveal that the depths equipped with boreholes catching the CI/CH complex vary from 70 to 800 meters from East to West while the average thickness of the reservoir CH is 50 meters and it mainly consists of coarse sandstone. Drilling penetrated more than 100 meters into the CI without reaching the base. The CI tank is composed of several layers of gravel and clay whilst the CI/CH aquifers flow rates range from 0.2 to 22.8 m3/h/m. So this is cause of great variability of the water potential within this aquifer. Lastly, the transmissivity coefficients are more important in the CH than in the CI, and the water flow average rates range respectively from 29 m/year to 7 m/year.展开更多
文摘A regional study connecting geolelectrical surveys with geology and hydrogeology was carried out in the western part of the Iullemmeden basin, precisely in the Dosso region in Niger. One hundred and four (104) vertical electrical sounds have been realized, among them nineteen representative were thus be used as parametric surveys. The local resistivity values of the geological formations of Quaternary range from 100 Ω⋅m to 1000 Ω⋅m (sands and lateritic sandstones). The Oligo-Miocene formation of the Continental terminal (Ct) shows resistivity values ranging from 1 to 5 Ω⋅m (brackish groundwaters) to 1500 Ω⋅m (clay sandstones) while the Upper Cretaceous formation of the Continental “hamadien” (Ch) indicates values ranging from 20 Ω⋅m (sandy clay) to 5000 Ω⋅m (clayey sandstones). The geological formations of Paleocene have values from 2 Ω⋅m (marls) to 60 Ω⋅m (calcareous marl), while the Precambrian basement exhibits values of granite around 300 Ω⋅m to 60,000 Ω⋅m. The update of the structural settings reveals many faults in the study area which explain both the shape of the basin and the geometry of the aquifers. Tectonics is also consistent with the hydraulic characteristics of aquifers. In addition, brackish groundwaters were identified as perched aquifer groundwaters in different depths in Dosso region. They probably come from the marine brines during the regression of the Paleocene Sea.
文摘This study was conducted in the region of Tahoua the northeastern part of the Southern Illulemeden sedimentary basin. In this region the transboundary aquifer system of Continental Intercalaire (CI) and the Continental Hamadien (CH) are potentially rich in underground water especially in free and captive aquifers. More, this water is the main source of drinking water for the populations, the animals and for agriculture and extractive industries. However, the population growth, the agricultural development, and the climate change have a real impact on the dynamics of groundwater and the exploitation of these resources. Hence, this study aims at analyzing the behavior of aquifers and assessing the impact of various natural and anthropogenic factors. Especially it matters to analyze the drilling parameters and cuttings, logging data and pumping test of nine new boreholes. The results reveal that the depths equipped with boreholes catching the CI/CH complex vary from 70 to 800 meters from East to West while the average thickness of the reservoir CH is 50 meters and it mainly consists of coarse sandstone. Drilling penetrated more than 100 meters into the CI without reaching the base. The CI tank is composed of several layers of gravel and clay whilst the CI/CH aquifers flow rates range from 0.2 to 22.8 m3/h/m. So this is cause of great variability of the water potential within this aquifer. Lastly, the transmissivity coefficients are more important in the CH than in the CI, and the water flow average rates range respectively from 29 m/year to 7 m/year.
