Groundwater Level Changes since 1978 in an African City on Basement Rocks: The Case of the CIEH Borehole in Ouagadougou (Burkina Faso)

Abstract

The 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 aquifer 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 anthropic effects Further quantitative interpretations of the CIEH piezometer record will require additional geophysical and hydrological investigations.

Analysis of stakeholder perceptions and practices related to climate change adaptation in Burkina Faso.

“…Burkina Faso is a Sahelian country, with 84% of the population economy and livelihoods based on the agricultural sector. According to a recent study about water resources assessment and management framework (MEE, 2001), agriculture alone accounts for more than 64% of the total water consumer demand. The irrigable areas are estimated at 233,500 ha, and only 14% was effectively explored (Evans et al, 2012).…”

“…Most farmers irrigated their crops twice a day, especially in the mornings and afternoons. These practices likely amplified the waste of agricultural water since evaporation was quite high (80% on average) in this region (MEE, 2001). Farmers need adequate technical advisory support on climate smart agricultural practices.…”

In Situ Observations and Lumped Parameter Model Reconstructions Reveal Intra‐Annual to Multidecadal Variability in Groundwater Levels in Sub‐Saharan Africa

“…We therefore made an initial estimate of hydraulic conductivity values based on the reported transmissivity values and an estimate of the saturated thickness under pumping conditions based on borehole logs, resulting in a range of 0.3-1.7 m day −1 . While Yameogo (2008) reports transmissivity, unconfined storage coefficient, and hydraulic conductivity for a number of sites across the city of Ouagadougou, Mouhouyouddine et al (2017) notes that no successful pumping tests have been undertaken at the observation borehole in Ouagadougou used for long-term monitoring in this research. No pumping test data are available for the remaining three sites (Dingasso, Binde, and Ouda), and no data for unconfined storage coefficients are available for any of the sites.…”

“…Using the same approach as Martin and Thiéry (1987), Filippi et al (1990) developed 1-D reservoir models for six of the sites (Bassinko, Silmissin, Niangoloko, Tibou, Arbinda, and Katchari), but only using <2 years of monitoring data. Mouhouyouddine et al (2017) subsequently also used the same approach to model observed groundwater levels at Ouagadougou from 1978-2015. Recently, Cuthbert, Taylor, et al (2019) used data from this site in a continental scale evaluation of controls on groundwater recharge processes.…”

“…The equations used in this AquiMod model structure are shown in Supporting Information S1. Soil water balance methods similar to the UN FAO method have been used as a part of the 1-D reservoir modeling previously undertaken at some of the sites, which resulted in acceptable model calibration of groundwater levels (Filippi et al, 1990;Martin & Thiéry, 1987;Mouhouyouddine et al, 2017). These methods have been widely applied in semiarid African settings for recharge estimation (see Wang et al, 2010, for a summary of studies).…”