TITLE:
Assessment of Seasonal Variation in Water Quality in River Rwizi Using Multivariate Statistical Techniques, Mbarara Municipality, Uganda
AUTHORS:
Walter Ojok, John Wasswa, Emmanuel Ntambi
KEYWORDS:
Principal Component Analysis, Factor Analysis, River Rwizi, Physico-Chemical, Water Pollution
JOURNAL NAME:
Journal of Water Resource and Protection,
Vol.9 No.1,
January
25,
2017
ABSTRACT: Assessment of seasonal variations
in surface water quality characteristics is an essential aspect for evaluating
water pollution due to both natural and anthropogenic influences on water
resources. In this study, temporal variations of water quality in river Rwizi
section within Mbarara municipality, Uganda, were assessed using multivariate
statistical methods. This river section is a major source of water for the
inhabitants of Mbarara municipality. Water samples from five sites were
analyzed for physicochemical parameters such as pH, EC, turbidity, temperature,
TSS, TDS, alkalinity, salinity, colour, NH3-N, , total hardness, BOD, COD,
DO, Ca, Mg, Fe, and Mn. About 50% of sites recorded colour above 800 Pt Co, 60%
of sites recorded turbidity above maximum permissible limit of 100 mg/l,
attributable to erosion and mineral matter. pH for dry season ranged between 6.5
and 8.5 whereas for rainy season was below 6.0. All study sites recorded total
Fe above 0.3 mg/l and Mn below 0.5 mg/l, attributable to chemical weathering of
host rock materials as well as from industrial effluent. About 60% of sites
recorded COD above 100 mg/l, 40% and 80% of study sites showed BOD above 50
mg/l in dry and rainy seasons respectively. Hardness ranged between 50 and 100
mg/l indicating that the water is moderately soft. Colour, turbidity,
alkalinity, TSS, TDS, salinity, pH, hardness, Fe, Mn, NH3-N, BOD,
COD, and DO were higher in rainy season, as a result of erosion, discharge of
domestic and industrial waste. Mg, Ca, and were
higher during dry season due to high evaporation of water from the river.
PCA/FA determined that 81.2% of the total variance was explained by the first
factor for the dry season and 69.2% for rain season. These results revealed
that water pollution resulted primarily from domestic waste water, agricultural
runoff and industrial effluents.