Status of water quality in the Dhaleshwari River and its effect on aquatic organism

The study was conducted to know the status of water quality in the Dhaleshwari river and its temporal changes over monsoon, post-monsoon and pre-monsoon seasons due to change of physicochemical parameters during the period from June 2011 to May 2012. The river starts off the Jamuna near the north-western tip of Tangail district with high potential for sheries production in this area. Over exploitation of fisheries resources, river bank erosion and human activities are gradually hampered the aquatic environment of the river. For existence and conservation of aquatic resources, it is essential to investigate the water quality and surrounding environment of the river. The results of the study showed that the concentrations of EC (Electric conductivity), DO (Dissolved oxygen), BOD (Biological oxygen demand), Hardness, Sodium, Potassium and Copper were within the standard limit as well as suitable for aquatic lives. The water pH was less than the standard i.e. slightly acidic, transparency was incalculable and TDS (Total dissolved solid) was increased in both post and pre-monsoon seasons. The content of Total Nitrogen, Phosphorus and Cadmium exceeded the permissible limit in all seasons. The excessive abundance of Total Nitrogen and Phosphorus made the river prone to eutrophication which ultimately resulted into degradation of water quality, phytoplankton blooms and change in fish production. This could be due to excessive agricultural activities near and adjacent to the bank of the river. The comparative study showed that most of the water quality parameters of the Dhaleshwari river were suitable for aquaculture of aquatic organisms as well as fishes.