Abstract:
The study was made to investigate the potential heavy metals and physico-chemical water quality of Lake Tana.
Water samples were collected from 15 sampling sites of the lake for the measurement of heavy metals, nutrients
and physico-chemical water quality indicators in both dry and wet seasons. Nutrients were determined by following
the standard procedures outlined in the American Public Health Association (APHA) using UV/Visible
spectrophotometer and heavy metals were measured using atomic spectrophotometry (AAS). There were
spatio-temporal variations in the physico-chemical water indicators and heavy metals in the lake ecosystem during
the study period. Higher concentrations of nutrients, electrical conductivity (EC) and total dissolved solid (TDS)
were recorded in sampling sites of effluents of the some resort and the major feeding rivers in all seasons.
The mean concentrations of heavy metals were Zn (1.66 mg/L, 1.04 mg/L), Cu (1.4 mg/L, 0.23 mg/L), Pb (0.75 mg/L,
0.25 mg/L), Mn (1.26 mg/L, 0.99 mg/L), Cr (0.07 mg/L, 0.2 mg/L), Cd (0.029 mg/L, 0.009 mg/L) in dry and rainy
seasons respectively. Where as in Gumara river; Zn (0.69 mg/L ,0.62 mg/L), Cu (0.88 mg/L, 0.2 mg/L), Pb (0 mg/L,
0.25 mg/L), Mn (0.11 mg/L, 0.45 mg/L), Cr (0.07 mg/L, 0.2 mg/L), Cd (0.069 mg/L, 0.008 mg/L) in dry and rainy
seasons respectively. In order to stop further deterioration of lake water quality and to eventually restore the
beneficial uses of the lake, management of agrochemicals in the lake watershed should be given urgent priority.
Keywords: Heavy metals, physico-chemical water quality, spatio-temporal variations, electrical conductivity.
Introducti
