The effect of trout farm effluents on the water quality parameters of Zaringol Stream (Golestan, Iran) based on NSFWQI and WQI indexes

Fish culture sites produce considerable volume of effluents which could have effects on water quality and downstream aquatic systems. the aim of this study was to assess the potential impacts of trout farm effluents on water quality of zaringol stream (golestan, iran) based on nsfwqi and wqi indexes. for this, physicochemical water quality parameters were measured each season from 14 stations during december 2009 to september 2010. the average value of nsfwqi was 53.21 and it showed spatial and temporal variation. the maximum value or best water quality condition (74.5) and minimum value of nsfwqi or the worst condition (50.93) belonged to stations 1 and 2 respectively. results of seasonal variations of nsfwqi showed that the maximum and minimum values were 59.62 and 53.82 in autumn and spring respectively. similar to the nsfwqi, the wqi index changed between different stations. stations 2 and 8 had the lowest value (0.76), station 7 had the highest (1.01) and the mean value was 0.88. although the temporal variations of wqi were low, the highest value was calculated for summer (0.94) and the lowest one (0.81) for autumn. according to the results of nsfwqi, wqi and physicochemical parameters, water quality condition of zaringol stream is average and need a change in strategies of water quality management in the area. it seems that effluents entering from trout farms in spring and summer are reasons of the decline in water quality and it is necessary to use treatment methods based on environmental standards to avoid the future risks.