#dissolved oxygen

The indiscriminate discharge of sewage, industrial, and a variety of water from human activities progressively alters and pollutes reservoir water. Investigation of the physicochemical in the water of Binday dam showed a fluctuation of phosphate during the months of October, November, and December. Similarly, low temperature was recorded in the months of September and December and nitrite increased during the month of December which failed to meet the Class C waters. Dissolved Oxygen, pH, electrical conductivity, biochemical oxygen demand, and total dissolved solids meet the standard measurement. Significant differences in physicochemical parameters were recorded between upstream and downstream during the months of September, October, November, and December except for DO, BOD, and EC. Fish identifications are exclusively found in the upstream and downstream namely, Oreochromis niloticus, Channa striata, Clarias gariepinus, Yanica hyalosoma, Carangidae sp., Glossogobius sp., and Glossogobius circumspectus classified as native species, and Sarotherodon melatheron and Gambusia affinis classified as invasive species. Fish distribution revealed that Carangidae sp. only thrives in the upstream whereas Gambusia affinis are exclusively found in the downstream.

Research revealed that the dissolved oxygen concentration in the Sitalakhyariver has been gradually deteriorated over the last decade and the temperature pattern of river water is also changing gradually. To assess the ecological integrity of river Sitalakya, this study is aimed at determining the relationship among surface water temperature, DO, and COD in the river as they affect each other, particularly to assess whether DO depletion of the river water is occurring due to water temperature changes or for the anthropogenic pollution made to the river. Subsequent to water quality testing for a period of five years following the standards methods in the laboratory, the statistical regression analysis of the concentration of DO in the raw water and the corresponding temperature and also the corresponding COD concentration in the water during the study period was made. The correlation analysis shows a poor relationship between DO and temperature of the raw water. The coefficient of determination is also derived showing R2 value 0.30 indicating a very weak relationship between surface water temperature and dissolved oxygen in this river. The correlation analysis between COD and DO was also made and the coefficient of determination is also derived showing R2 value 0.70 indicating a very good correlation between the two. It is apparent that with the increase of COD concentration in the surface water DO concentration decreases proportionately. These results showed clearly that DO content of this river depend on the organic waste dumped in the river and not surface water temperature.