The residual effect of fish farms on the water quality of the Euphrates River, Iraq.

Abstract

This is the first study using spatial distribution maps and water level fluctuations to highlight the impact of fish farms on the water quality of the Euphrates River. Physical and chemical characteristics were estimated before, during, and after the rainy season (October – December 2018) when the water velocity and the level of the river were in fluctuation. The water depth in the study area fluctuated between 4 and 4.5 meters. Field and laboratory analyzes were carried out, obtaining the ecological indicators of Dissolve Oxygen (DO), Biological Oxygen Demand (BOD5), Water Temperature, pH, Total Dissolved Solids (TDS), Nitrate (NO3 -), Phosphate (PO4 3-) and Turbidity (NTU). The impacts of fish farms cages on river water for (DO, BOD5, and NO3 -) have been determined using multi spatial distribution maps. The results showed that the increase of NO3 - concentration within the fish cages site A is more by 51 times than its normal concentration at the point A0, whereas, the decrease in DO concentration is reached 31%. The effective contaminated distance in the direction of downstream fish farm reaches more than 60 meters. The spatial concentration rate of the nitrate enrichment with the flow direction ranges from 0.58 to 0.60 mg/L for each meter. At the same time, the amount of dilution gradient ranges from 0.30 to 0.32 mg/L/m during the monitoring period. The spatial concentration rate of BOD5 enrichment was 0.085, 0.08, and 0.06 mg/L/m, while the amount of dilution gradient was 0.04, 0.03, and 0.06 mg/L/m during October, November, and December, respectively.