Abstract
The current study was carried out to examine the spatial and temporal variations of physicochemical water quality parameters of Lake Bunyonyi. The observations were made on the surface water of Lake Bunyonyi for 1 year to determine the water quality. The basic 12 variables used to determine the quality of water were measured monthly at nine stations. Water temperature, dissolved oxygen (DO), turbidity, electric conductivity (EC), pH and Secchi depth (SD) were measured in the field, while parameters like total nitrogen (TN), total phosphorus (TP), nitrite-nitrogen (NO2-N), nitrate-nitrogen (NO3-N), soluble reactive phosphorus (SRP) were determined following APHA 2017 standard guidelines for physicochemical analysis. Taking into account standard guidelines for drinking water by the Uganda National Bureau of Standards (UNBS) and the World Health Organization (WHO), the water quality index (WQI) was used to determine the water quality. Temperature, DO, pH, turbidity and EC did not differ significantly among the study stations (p > 0.05) but showed significant temporal variations among the study months (p < 0.05). Likewise, TN, TP, NO2-N, NO3-N and SRP did not differ significantly among the study stations (p > 0.05) but showed significant temporal variations among the study months (p < 0.05). The WQI values ranged from 28.36 to 49 across and from 28.2 to 56.2 between study months with an overall mean value of 36.9. The measured water quality variables did not exceed the UNBS and WHO standards for drinking water in all months and at all stations. According to these values, the water quality of Lake Bunyonyi generally belongs to the ‘good’ class in terms of drinking water quality based on the WQI classification. The study findings are fundamentally important for policy makers in setting guidelines for effective lake management.
Highlights
Water is a vital element in human life, it is most threatened worldwide [21, 48]
Electric conductivity values varied between 241.1 ± 11.1μS/ cm and 266.8 ± 61.9 μS/cm obtained at Mugyera (M3) and Harutinda (U2), respectively
We conclude that the quality of water in Lake Bunyonyi is generally good for drinking as per water quality index (WQI) classification
Summary
Water is a vital element in human life, it is most threatened worldwide [21, 48]. High levels of pollutants such as persistent organic chemicals in the lake ecosystems may make the water unfit for recreation, swimming/ bathing, drinking and fishing, while excess nutrients (nitrogen and phosphorus) massive algal blooms that result in eutrophication and its associated effects on aquatic life [29, 41, 48, 55, 56]. Aquatic environments require appropriate maintenance through interventions that require systematic knowledge of the ecosystem functions controlling the lake as a source of water and a habitat for both aquatic and benthic organisms. Since many factors are responsible for the deterioration of water quality in a given water body, the need for periodic monitoring of the lakes’ water chemistry is absolute [18]
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