Small Reservoirs, Landscape Changes and Water Quality in Sub-Saharan West Africa

Jean-Christophe Poussin,Gerald Forkuor,Franck Lalanne,Olufunke Cofie,Philippe Cecchi,Jean-Yves Jamin

doi:10.3390/w12071967

Abstract

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.

Highlights

Small reservoirs (SRs) are important artificial water resource structures in semi-arid environments around the world and noticeably in Sub-Saharan Africa [1]
We found that the changes of the PIM contribution to the Suspended Particulate Matter (SPM) loadings between the two dates were sensitively associated to the evolution of cropland within
This study sought to fill this gap by relating demography and land use and land cover (LULC) changes at different geographical scales and water quality changes in a decade

Summary

Introduction

Small reservoirs (SRs) are important artificial water resource structures in semi-arid environments around the world and noticeably in Sub-Saharan Africa [1]. They harvest rainwater during the rainy season and are often the only source of water for multiple uses such as domestic water supply, livestock watering, irrigation, etc., and in delivering local employment opportunities during the dry season. 1/3 perennial), most of which were constructed between 1974 and 1987 in response to the Sahel droughts of the 1970s and 1980s [2]. Both improved household income and food security associated with their presence and uses are universally acknowledged by riverine populations [1]

Methods

Discussion

Conclusion