THE PHYSICO-CHEMICAL AND BIOLOGICAL CHARACTERISTICS OF SELAMEKO MANMADE RESERVOIR, DEBRE TABOR, SOUTH GONDAR, AUGUST 2009 TO MAY 2010

The physico-chemical and biological characteristics of Selameko reservoir, Debre Tabor, South Gondar, were studied for one year from August 1/2009 to May 5/2010. Water quality parameters, such as temperature, transparency, water depth, dissolved oxygen, pH, total dissolved solids, phosphate, nitrate, and silicate were measured in situ from two sites (littoral and open water zone) of the reservoir. All biological parameters were analyzed in Tana Fisheries and other Aquatic Organisms Research Center.  Water temperature  reservoir  ranged from 18.7 to 24.2°C, water depth (only for open zone) from 10.5 m to 13.04 m, pH from  7.01 to 8.01, DO from 5.0 to 6.15 mg/l, transparency depth from 32 to 97 cm, TDS from 67.1 to 137.2 ppm, NO₃-N from  0.1 to 2 mg/l, PO₄-P from 0.08 to 0.83 mg/l and Silicate from  0.09 to 22.5 mg/l. Chlorophyll-a varied from 11.02 to 39.29 µg/l. ANOVA result of the physic-chemical parameters including chlorophyll-a showed significant difference among seasons and between sites (p<0.05). A total of 7 families, 36 genera from 3 groups (Diatom, Blue green algae and Green algae) of phytoplankton were identified during the study period. From all groups, diatoms were the most abundant at both sites and Blue- green algae were the least abundant. Phytoplankton abundance showed highly significant difference among seasons and between sites (ANOVA, p<0.05). A total of 16 genera from 3 taxonomic groups of zooplankton were recorded during the study period.  Zooplankton had significant difference among seasons and between sites (ANOVA, p<0.05), but not Rotifera between in sites. The reservoir water provided lots of services to the beneficiaries and the surrounding communities, such as irrigation; watering livestock, washing clothes and utensils, recreation, etc. The study concluded that the ecology of the reservoir is under strong anthropogenic pressure like presence for agricultural practice near the peripheral of reservoir, absence of wetland vegetation due to overgrazing and deforestation, presence of accumulated municipal wastes and sediments, dam crack, etc. As a result, some of the physico-chemical parameters were not suitable for fisheries, and the reservoir water was eutrophic (productive) throughout the year. To avoid such anthropogenic pressure, basin and reservoir management are recommended.