Spatial and seasonal variations in physico-chemical features of alkaline saline lake, Lake Shalla, Ethiopia.

Solomon Wagaw, Seyoum Mengistou, Abebe Getahun

Abstract


Lake Shalla is a vital resource for considerable aesthetic, economic, scientific and ecological values. However, the lake is under pressure from various anthropogenic activities and climatic change. Hence, this study evaluated spatio-temporal variations in the physico-chemical parameters of the lake. Water samples were collected from four sampling stations from January to December 2018 and analyzed at Limnology laboratory, Addis Ababa University. Except DO which showed only significant seasonal variation, the other significantly varied among sites and between seasons (ANOVA: P < 0.05). pH (10.08), Alkalinity (391.1 meq/L), NO3-N (0.17 μg/L), NH3-N (108.78 μg/L), SiO2(1.09 mg/L), TP(2.03 mg/L) and SRP (1.25 mg/L) were recorded at Shalla Gike Shore (SGS) and were significantly different compared with other sites. Mean concentrations of pH (10.1), Alkalinity (380.5 meq/L), NO3-N (0.19 μg/L), NH3-N (113.69 μg/L), SiO2 (1.16 mg/L), TP(2.14 mg/L) and SRP (1.45 mg/L) were recorded during rainy season, whereas DO (8.12 mg/L), EC (33.99 mS/cm) and salinity (21.34 g/L) were recorded during the dry season and were significantly different. Comparison with previous studies indicated long term increasing trend for pH, Alkalinity, Salinity, Eectrical conductivity, NO3-N, NH3-N, SRP and TP, while SiO2 showed a decreasing trend. These changes might be attributed to increasing anthropogenic activities in the catchments, biogeochemical process in the lake, geomorphic and hydrological characteristics of the region or climate change. The results of this study might be used as inputfor the long term planning and management of the lake.


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