<p>The lack of adequate information on groundwater recharge mechanisms in the basement rock area of Sahelian regions does not allow to estimate recharge rates. Thus, this study, which aims to improve the knowledge of the groundwater recharge mechanisms of the Tougou (catchment of 37 km<sup>2 </sup>representing a basement rock in Sahel of West Africa) aquifers was initiated. The first step was to characterize the geology in terms of geometry and structure. The ERT profile (1.2 km length) crossing perpendicularly the river and lithologs from 10 observation wells (Average depth: 25m) and 1 borehole (Depth: 60 m) were used to make the correspondence between geological and geophysical data. The second step was to characterize vertically and laterally aquifers recharge mechanisms under the ephemeral river and two river banks. Hence, hourly to daily groundwater levels, electrical conductivity, and temperature of groundwater have been measured in those 10 observation wells and 1 borehole (Period: 2016-2020). The river water levels and the rainfall were also collected. The cross-correlation function was used between the rainfall or river water levels and the hydraulic heads time series. The geological characterization showed from top to bottom:</p><ul><li><strong>Residual soils: </strong>1 m to 2 m thick, present in the riverbed and on the right bank;</li> <li><strong>Laterite </strong>(lateritic clays and lateritic cuirass): 2 m to 14 m thick, absent in the riverbed and present on the two banks;</li> <li><strong>Laterally continuous clayey saprolite</strong>: 10 m to 22 m thick;</li> <li><strong>Weathered schist:</strong> 32 m thick in the river. A bedrock was found at a depth of 55 m.</li> </ul><p>This geological conceptual model was a grounding for interpreting the results incurred from other data collected. It was ascertained that the weathered schist aquifer below the river is semi-confined (Average water depth: 9.5 m < top: 25 m) and vertically recharged by the saprolite aquifer. Laterally, the clayey saprolite aquifer is recharged by two main flows from:</p><ul><li><strong>The river:</strong> the electrical conductivity and temperature of the groundwater in the clayey saprolite aquifer below the river vary at the same time as the water table increases during the rainy season. In addition, mean hydraulic head differences of +0.3 m and +2 m have been observed between the piezometer located in the river and respectively, the piezometer located at 20 m from the river on the left bank and other piezometers located on the right bank (up to 600 m from the river). A maximum good cross-correlation between hydraulic heads and river water levels rather than with rain was found in all piezometers, but mostly in the one located in the river (cross-correlation = 0.56). These indicate an indirect recharge process.</li> <li><strong>The left bank:</strong> An mean hydraulic head difference (+3 m) which is related to a transfer of hydraulic pressure from probably a nearby recharge area was noted between the piezometers located at 300 m and the riverbed.</li> </ul><p>For further studies, the information obtained will be used to estimate the recharge through different methods including numerical modeling.</p>

This study aims at identifying possible correlations between shapes, types of geophysical anomalies and borehole productivity according to geological and hydrogeological contexts. The methodology adopted was a two-pronged one-the first step sought to: (i) interpret the electrical resistivity values from horizontal profiling and vertical electrical sounding implemented in Seno province that preceded the drilling of 513 boreholes; (ii) interpret data from pumping tests carried out on boreholes having a discharge superior to 1 m 3 /h ("positive borehole") by using Cooper-Jacob's method. In the second step, according to geology, authors tried to identify possible correlations between each of the qualitative geophysical parameters: «shape of anomaly», «type of anomaly» and «type curve» on the one hand, and hydrogeological parameters such as discharge, alteration thickness, transmissivity and saturated level on the other. The results of this study have shown that the chances of having a positive borehole in Seno province are higher when the type of anomaly is TCC (80%), shape of anomaly is "W" and when type curve is "H" (80%) for all geological formations. Granitic formations are those that record higher discharges while schists record high transmissivity values.

This study aims to estimate the hydrodynamic properties of soils under various agricultural practices in the Tougou catchment in northern Burkina Faso. The methodology adopted is based on the determination of the unsaturated hydraulic conductivity and capillary sorptivity close to saturation. This method relies on the measurement of the transient infiltration flux at the soil surface with imposed hydraulic head varying from-60 to-20 mm. These tests are carried out on control, stony line, half-moon and zai plots. The results show a difference in hydrodynamic parameters according to the agricultural practices. The unsaturated hydraulic conductivity is 33.1 cm/h, 13.1 cm/h, 20.3 cm/h and 4.0 cm/h for zai, control, stony line and half-moon plots respectively. The unsaturated hydraulic conductivity is 33.1 cm/h, 13.1 cm/h, 20.3 cm/h and 4.0 cm/h for zai, control, stony line and half-moon plots respectively. The pores participating to water transfer also differ. The mean size of drainable pores is 43.7, 56.2, 22.3 and 87.2 μm on control, stony line, half-moon and zai plots respectively.