Assessment of the water quality of the Niger River in Bamako, Mali, based on the Water Quality Index

Abstract

The Niger River, threatened by human activities, is mainly the drinking water source for the population of Bamako city. This study assesses the trend of Niger River pollution in Bamako using the Water Quality Index (WQI). Fourteen parameters, namely Turbidity, Potential of Hydrogen (pH), Electrical Conductivity, Dissolved Oxygen, Total Dissolved Solids, Biochemical Oxygen Demand (BOD5), Chemical Oxygen Demand (COD), Nitrate, Nitrite, Ammonium, Phosphate, Sulphate, Chloride and Copper, were employed to characterise the Niger River water quality during the period from 2016 to 2020. Parameters were measured at 15 sampling locations. High values of Turbidity, pH and high concentrations of BOD5, COD, Nitrite, Ammonium and Phosphates were recorded. The results showed that the Niger River water quality was good for 4 months and poor for 5 months during the dry season in a low flow period. Moreover, the water quality was poor during the 3 months of the wet season in the high flow period. The calculated WQI average values ranged from 75 to 100, indicating very poor water quality from upstream to downstream of Bamako city. Therefore, the Niger River water is polluted and cannot be used for drinking or industrial uses without any treatment.

A multivariate approach to assessing the water quality of the Bamako reach of the Niger River in Mali as irrigation water

“…Thus, they support multiple index approaches to irrigation water quality assessment (Ezea et al, 2022). This study's results confirm Sangare et al's (2023) recent findings about using the Niger River water for irrigation. Those authors determined the pollution status of the Niger River based on the simple water quality index (WQI).…”

“…The concentration of all parameters, except for NO 3 − , PO 4 3− , and K + , is higher during the high flow (wet season) compared with the low flow (dry season). The high concentration of the parameters in the wet season could be explained by the cumulated effects of rain (runoff) and discharges from households and industrial units in the capital city of Bamako (see Sangare et al, 2023). In the same line, Dutta and Sarma (2018) explained that seasonal variation of the parameters' concentration was due to the high land erosion and direct discharge from stormwater drains.…”

“…The data pertained to the average monthly flow of the Niger River over 5 years, from January 2016 to December 2020. Sample locations are located at geographic coordinates: West longitude (X): −7.99845982; North latitude (Y): 12.6312999725342 in Bamako city (Sangare et al, 2023). The physicochemical parameters were collected from the “Laboratoire Nationale de l'Eau” (National Water Laboratory).…”

Evaluation of SENTINEL-2 products-based algorithms in estimating water pollutants of the River Niger in Bamako

“…This analysis shows two clear trends during the dry and rainy seasons, which describe the instability of the water quality of the Niger River with a more significant temporal variability during the rainy season than during the dry season. The variation in the parameters during the rainy season is explained by the effect of runoff water discharged into the river, which is most often loaded with domestic and industrial wastewater without appropriate treatment in the city of Bamako [66,67]. The same pattern emerged in other studies that reported that most water quality parameters were slightly higher during the wet season than during the dry season [56,66,70].…”

“…The increasing of Chlorophyll-a from May to November was observed during all the high flow periods (wet season) across Bamako city. This high distribution reveals growth of aquatic plants and is due to anthropogenic sources of nutrients that affect the ecosystem and reduce water quality, which is a threat to human consumption [66,67].…”