The physio-chemical characteristics of a highland crater lake and two reservoirs in north-west Amhara Region (Ethiopia)

Abstract

Seven water quality parameters were monitored in one highland Crater Lake (altitude 2500 m) and two reservoirs (altitude 1800 m) in the period December 2004 to July 2005. Surface water temperature ranged from 19 to 26°C, dissolved oxygen from 4 to 10 mg rt, turbidity from 5 to 30 NTU, pH from 7.7 to 8.7, conductivity from 55 to 185 μS cm^-1 , total dissolved solids from 33 to 150 mg l^-1 , and nitrate from 2.6 to 4.5 mg l ^-1 N0₃ -N. The lowest values, except for dissolved oxygen and pH were observed in Zengena Crater Lake. The two reservoirs showed elevated levels of nutrients and total dissolved solids, high turbidity, and high conductivity. This was the result of a high sediment and nutrient load from the catchments. These results show that these reservoirs are heavily influenced by agricultural practices and municipal effluent. We recommend that water quality management measures like controlling allochthonous nutrient loadings should be taken to stop eutrophication in these reservoirs.

Key words: Tropical limnology, East Africa, f ater quality management