Assessment of Agricultural and Mining Pollutions of Waterbodies within the Nakanbé Basin (Burkina Faso): The Case of the Goinré, Ziga and Bagré Reservoirs

Abstract

Agriculture is harming its own future through soil degradation and pollution of the water that it generates. The different chemical analyses carried out on surface waters and the land surveys carried out in the Nakanbé basin have shown that agricultural practices contribute to water pollution. The monitoring of nitrate, ortho-phosphate and BOD5 levels in the dams of Goinré, Ziga and Bagré during the period from August to December revealed that agricultural practices lead to variation in these parameters. The average values for nitrates are 0.833 mg/L in the Goinré fresh waterbody, 1.372 mg/L in the Ziga reservoir, and 1.267 mg/L in the Bagré fresh waterbody. As for ortho phos- phate, mean values are 0.357 mg/L in the Goinré reservoir, 0.157 mg/L in the Ziga reservoir and 0.123 mg/L in the Bagré reservoir. These average values are higher than the norms established by Nisbet and Vernaux (1970) for eutrophication. Nitrates and orthophosphate are the elements that contribute to the eutrophication of water surfaces in the Nakanbé basin, although this eutrophication is of low intensity. Of all pesticides encountered in our study sites, 45% are registered by the Sahelian Pesticides Committee (CSP): 35% are non- accredited and 20% are unknown in the global list authorized by the CSP in 2010.