The aim of this study was to assess the potential impact of Trout farm effluents on water quality of Zaringol stream based on NSFWQI and WQI indexes. Some physicochemical water quality parameters were measured from 14 point during December 2009 to September 2010 seasonality. The average value of NSFWQI is 53.21 and it shows 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) belongs to point 1 and 2 respectively. Results show that the maximum and minimum of its values are estimated for autumn and spring which are 59.62 and 53.82. Similar to the NSFWQI, the WQI index changes between different stations. Point 2 and 8 have the lowest value (0.76), point 7 has the highest (1.01) one and the mean value is 0.88. Although the temporally variations of WQI are low, the highest value is calculated for summer (0.94) and the lowest one (0.81) referred to autumn Therefore, water quality status of Zaringol stream is average and need to change strategies of management and sanitary programs. It seems that effluents entering from Trout farms were located around Zaringol stream (point 2 and 8) and increasing those activities in spring and summer are reasons of the decline in water quality especially in these points. It is necessary to manage the production rates and use of wastewater treatment methods based self-purification power of Zaringol stream and environmental standards to avoid the future risks.