Comparative Study of Anthropogenic Activities Influences on Water Qualities of Boundiali, Korhogo and Ouangolodougou Dams (Cote d'Ivoire)

Abstract

Aims: This study was conducted in the context of water resource security. The main objective was to highlight human activities that could have a significant impact on dams water quality of the dams of Boundiali, Korhogo, and Ouangolodougou. Study Design:  Water samples were analysed. Then, water quality and pollution levels have been evaluated. Finally, waters pollution origins were highlighted. Place and Duration of Study: The First sampling campaign was carried out during the rainy season from August to September 2021, and the second in the dry season from December 2021 to January 2022, at the Boundiali, Korhogo, and Ouangolodougou dams. Methodology: The adopted methodology consisted of water characterisation in these infrastructures and their compliance comparison with the WHO drinking water supply standards. Waters characterization concerns the following parameters: pH, temperature, electrical conductivity and dissolved oxygen, chemical oxygen demand (COD), biological oxygen demand (BOD5), nitrate (NO₃-), nitrite (NO₂-), ammonium (NH4+), iron (Fe), manganese (Mn), total phosphate (POᵌ-), lead (Pb), arsenic (As), cyanide (CN), mercury (Hg), organohalogen (POH) and organophosphorus (POP) pesticides and carbamates (CAR). Subsequently, quality and pollution indices were determined in order to provide an overview of the quality and pollution levels of these resources. Then, surveys were carried out with a view to identifying sites likely to be responsible for pollution. Finally, similarities and divergences in human activities that are the source of this water quality degradation were noted. Results: Characterization results show that these waters have relatively neutral pH values with relatively low electrical conductivities. Metals (iron and arsenic), nitrate, phosphorus and pesticides (POPs and POHs) have concentrations above the WHO drinking water standard. Quality and organic pollution indices indicate that these dams’ waters have very poor quality in rainy periods and are not drinkable in dry periods with moderate pollution. WQIs results are considered to be high, with 477.620 for Boundiali, 130 for Korhogo and 147.66 for Ouangolodougou in dry season, while WQIs were 83.467 in Boundiali dam, 190.6404 in Korhogo and 94.81 in Ouangolodougou in dry season.  In Boundiali, OPI has a high value of 3.667 in the rainy season and 2.667 in the dry season. At Korhogo, the OPI level has a constant value of 2.33 in both seasons. In Ouangolodougou, IPO is 3 in rainy season and 2,667 in the dry season. Field surveys confirmed that the quality of these resources is influenced by human activities, particularly agricultural practices in the immediate perimeters, which are the main pollution factors in Boundiali and Ouangolodougou, unlike Korhogo, where the main sources of pollution are non-seasonal activities such as sewage from riparian houses, livestock farming, artisanal activities and quarries. Conclusion: Waters from these three dams have different pollution sources such as natural incomes, but anthropogenic activities remain the main pollution source.