| Accueil | << 1 >> |
|
Cecchi, P., Forkuor, G., Cofie, O., Lalanne, F., Poussin, J. - C., & Jamin, J. - Y. (2020). Small Reservoirs, Landscape Changes and Water Quality in Sub-Saharan West Africa. Water, 12(7), 1967.
Résumé: Small reservoirs (SRs) are essential water storage infrastructures for rural populations of Sub-Saharan West Africa. In recent years, rapid population increase has resulted in unprecedented land use and land cover (LULC) changes. Our study documents the impacts of such changes on the water quality of SRs in Burkina Faso. Multi-temporal Landsat images were analyzed to determine LULC evolutions at various scales between 2002 and 2014. Population densities were calculated from downloaded 2014 population data. In situ water samples collected in 2004/5 and 2014 from selected SRs were analyzed for Suspended Particulate Matter (SPM) loads, an integrative proxy for water quality. The expansion of crop and artificial areas at the expense of natural covers controlled LULC changes over the period. We found a very significant correlation between SPM loads and population densities calculated at a watershed scale. A general increase between the two sampling dates in the inorganic component of SPM loads, concomitant with a clear expansion of cropland areas at a local scale, was evidenced. Results of the study suggest that two complementary but independent indicators (i.e., LULC changes within 5-km buffer areas around SRs and demographic changes at watershed scale), relevantly reflected the nature and intensity of overall pressures exerted by humans on their environment, and locally on aquatic ecosystems. Recommendations related to the re-greening of peripheral areas around SRs in order to protect water bodies are suggested.
|
|
Fowe, T., Karambiri, H., Paturel, J. - E., Poussin, J. - C., & Cecchi, P. (2015). Water balance of small reservoirs in the Volta basin: A case study of Boura reservoir in Burkina Faso. Agricultural Water Management, 152, 99–109.
Résumé: Effective water resources development and management is crucial for sustainable economic growth and poverty reduction in many developing countries. In West Africa, large numbers of small reservoirs with volumes from 104 to 107 m3 play a considerable role in maintaining and developing activities in remote areas and in providing irrigation water for agriculture and supply water for both livestock and people. The lack of baseline data on reservoir operation hinders their optimal management. The objective of this study was to enhance the knowledge of water resources of the small reservoirs in order to improve their management in the context of multiple uses. This study was carried out on a small reservoir located in Southern Burkina Faso which was monitored for 2 years (from April 2012 to April 2014). A simple approach based on the mass conservation equation was developed for estimating reservoir fluxes. For a short hydrological monitoring period, the rainfall, evaporation and reservoir filling patterns revealed a different hydrological balance of the reservoir between these 2 years. A decrease of 32% in the annual rainfall leads to a 50% reduction in the annual runoff coefficient. The results showed that about 60% of water was lost by evaporation, whereas less than 20% of water caught in the reservoir was withdrawn for various uses. The available water resources in the studied system are largely sufficient to satisfy the current demands. There are still possibilities for developing uses of water storage and for enhancing the irrigation potential of the small reservoir. This analysis indicates that small reservoirs are under-performing. The results highlighted that estimating water fluxes in a reservoir is a central task to support water management authorities and stakeholders in operational strategies for water supply and irrigated agriculture.
Mots-Clés: Burkina Faso; Hydrological monitoring; Small reservoirs; Water balance; Water use
|