The conceptualization of hard rock aquifers in terms of their geometry and structure has undergone considerable progress over the last two decades. Despite these advances, hydrogeologists are still divided by the models used to describe two central concepts: (i) the influence of weathering processes on hydraulic conductivity; (ii) the influence of tectonics on the hydraulic conductivity of hard rock aquifers. In order to provide further insight into this debate, the present study proposes a conceptual model for hard rock aquifers, based on an integrated hydrogeological and geophysical approach, using information acquired at different scales. The data and observations used for this case study were derived from the Sanon experimental site, located in Burkina Faso, which is presently exposed to a Sudano-Sahelian climate. The methodological approach consisted firstly in developing a description of the site's weathering profile at the scale of a borehole, based on lithologs and electrical resistivity logs. In a second step, the site's ridge to ridge (longitudinal) weathering profile was established from several 2D resistivity sections crossing a maximum number of lineament structures, which in some prior studies were considered to be the superficial manifestation of tectonic fractures. The results show that at that scale the weathering profile is comprised of three main layers, which from top to bottom are referred to as: the saprolite, the fissured layer and the fresh rock. This weathering profile model is consistent with other models proposed in recent years, suggesting that the hydraulic conductivity of hard rock aquifers is a consequence of weathering processes, rather than tectonic fracturing. Tectonic fractures are not visible on the 2D sections of the ridge to ridge profiles, and the lineaments originally thought to be overground representations of tectonic fractures are likely to have different origins. The lack of a substantial correlation between tectonic lineaments and fractures appears to account for the high incidence of negative boreholes in hard rock aquifers, where the siting of drillings has systematically been 3 based on lineament studies and on geophysical studies looking for vertical fractures such as profiling and vertical electrical sounding. There is thus a need to revise current hydrogeological concepts and methodologies to site wells based on tectonic fractures represented by lineaments.

This paper assessed the current and mid-century trends in rainfall and temperature over the Mono River watershed. It considered observation data for the period 1981-2010 and projection data from the regional climate model (RCM), REMO, for the period 2018-2050 under emission scenarios RCP4.5 and RCP8.5. Rainfall data were interpolated using ordinary kriging. Mann-Kendall, Pettitt and Standardized Normal Homogeneity (SNH) tests were used for trends and break-points detection. Rainfall interannual variability analysis was based on standardized precipitation index (SPI), whereas anomalies indices were considered for temperature. Results revealed that on an annual scale and all over the watershed, temperature and rainfall showed an increasing trend during the observation period. By 2050, both scenarios projected an increase in temperature compared to the baseline period 1981-2010, whereas annual rainfall will be characterized by high variabilities. Rainfall seasonal cycle is expected to change in the watershed: In the south, the second rainfall peak, which usually occurs in September, will be extended to October with a higher value. In the central and northern parts, rainfall regime is projected to be characterized by late onsets, a peak in September and lower precipitation until June and higher thereafter. The highest increase and decrease in monthly precipitation are expected in the northern part of the watershed. Therefore, identifying relevant adaptation strategies is recommended.Climate 2019, 7, 8 2 of 17 Furthermore, in tropical Africa a significant increase in temperature, about 0.15 • C per decade, was detected over the period 1979-2010 [5]. Consequently, high fatality rates are recorded in developing countries because of their high reliance on natural resources and their limited coping capacities [6]. Several authors highlighted that, since the 1970s, the number of natural disasters (flood, drought, windstorm, epidemic and famine) has been increasing in sub-Saharan Africa [7][8][9]. In 2012, central and western Africa were hit by severe floods which affected 1,538,242 people and caused 340 deaths as of September of that year. Moreover, flood events of 2010 have been recorded in West Africa as one of the most disastrous during the last decade. In 2010 only, Benin lost about USD 262 million [10], whereas Togo recorded about USD 43.934 million as damage and loss in the same year [11].Thus, there is a need to carry out future climate analysis in order to foresee potential hazards and ultimately to develop appropriate strategies to combat them. According to the fifth assessment report AR5, "global surface temperature change for the end of the 21st century is likely to exceed 1.5 • C relative to 1850-1900 for all RCP scenarios except RCP2.6" [12]. However, it is clear that climate-change impacts will be time and location specific [13]. Therefore, undertaking climate projection at regional and local level will contribute to more accurate and relevant actions towards human security.As in many other watersheds in the ...

This study evaluates the impacts of land use and climate changes on daily discharge in Ouémé river basin at Bétérou outlet. Observed rainfall and temperature over 2002–2008 and land use data of 2003 and 2007 were used. Corrected rainfall and temperature data, under RCP4.5 and RCP8.5 scenarios from regional climate model REMO were considered. Two land use scenarios from RIVERTWIN project were used. The first one, Land Use A (LUA), is characterized by stronger economic development, controlled urbanization, implementation of large-scale irrigation schemes, and 3.2% population growth per year. The other one, Land Use B (LUB), is characterized by a weak national economy, uncontrolled settlement, and farmland development as well as 3.5% population growth per year. Four climate and land use combined scenarios (LUA + RCP4.5, LUA + RCP8.5; LUB + RCP4.5, and LUB + RCP8.5) were used for forcing LISFLOOD hydrological model to estimate future discharges at 2050. As a result, during calibration and validation, the LISFLOOD model showed high ability to reproduce historical flows of Ouémé River at Bétérou outlet with Nash–Sutcliffe efficiencies greater than 90%. Future discharges simulations show general increase for all land use and climate combined scenarios for all time horizons until 2050. The increase is more exacerbated under the combined scenarios using LUB than the ones using LUA. Increase of river discharge varies between 7.1% and 52% compared to the mean of the reference period 2002–2004. These findings highlight growing challenges for water resources managers and planners. Moreover, they emphasize the need to address potential climate and land use changes’ impact on water resources. Then, developing water management plans, strategies to reduce flooding risks must be considered.