Spatio-temporal variation of nutrients in the Gagnoa reservoir (Western Central of Ivory Coast)

Résumé

Many peri-urban bodies of water are irreversibly damaged by eutrophication around the world. This study was carried out to know the spatial and temporal dynamics of nitrogen and phosphorus compounds contained in Gagnoa’s water reservoir and in its tributaries. During the long rainy and dry seasons from 2005, 2011 to 2013, nineteen sites’ waters, from springs, rivers and the reservoir permitted to analyze nutrients with the colorimetric method using a spectrophometer 2400/HACH LANGE. The values of nitrogen compounds showed a significant difference (p ˂ 0.05) during spatiotemporal variation. The water reservoir deemed to be at mesotrophic to eutrophic stage is more enriched with nutrients in the rainy season with a decrease in transparence and in chlorophyll a. This is explained by the use of fertilizers on the studied watershed, wastewater discharges, laundry doing and animals dejecta. These findings could be used as the basis for the setting-up of an integrated management plan for the water reservoir and its watershed.