Assessing the effects of aquaculture farms on water quality of Haraz and Tajan rivers

Constructing cold-water fish farms along Haraz and Tajan rivers is done without any scientific investigations. Little attention has been paid to the distances between farms. Moreover, the farms lack wastewater treatment facilities, and untreated effluents are easily discharged into the surrounding rivers. In the present study, we have investigated the impacts of aquaculture farms on water quality parameters in Haraz and Tajan rivers. We have analyzed quantitative and qualitative effects of farms effluents on water physicochemical parameters of these two rivers. Three different farms in each river were selected. For each farm, samples were collected from before farm inlet (control station), and two other stations, one at 50-100 m (where the farm effluent enters the river) and one at 1.5-2 km (to assess the self-purification potential) downstream of the farm. In total, 9 stations in Haraz river and 5 stations in Tajan river were selected. The results showed that both Haraz and Tajan rivers have the potential of purifying the effluents discharged by aquaculture farms. However, increasing the number of these farms in the future and also releasing untreated effluents may cause important problems for these rivers. It seems, according to the present study, that self-purifying potential at 1.5-2 km downstream of the farms is considerable. Therefore, considering this distance in the construction of aquaculture farms can help in maintaining the health of the river ecosystem. In addition, owners of the farms should be asked to use some facilities for treating the effluents.