Investigation on the temporal and spatial variation of Ortakand River water quality due to trout farms effluent

In recent years, activities on trout fish farming is developed significantly in Ortakand River. Fish production may have huge impact on the river ecosystem if an environmental rule is neglected. This research was carried out in Ortakand River in Kalat city in Khorasan Razavi with the aim of investigation of fish production projects effluent effect on the river water quality. Two fish farms and seven stations were selected and during one year in each season, water samples were collected. The samples were analyzed in the laboratory for determining some physic-chemical and biological parameters of water samples. The results showed that the average of these parameters were within a range between 13.3-15 °C of temperature, 7.9-8.1 of pH, 354-732 mmhos/cm of EC, 8.4-9.6 mg/L of DO, 1-3.7 and 2.5-13.9 mg/L of BOD5 and COD, respectively. The results showed that BOD5 and COD concentration had a significant increasing toward upstream (p<0.01), spatially. Meanwhile, amount of DO showed a significant decrease (p<0.01), temporaly. This research revealed that changes in concentration of BOD5, COD and DO were dominantly due to fluctuations of environmental conditions and activity rates of the farms. Although, the amount of COD and BOD5 in fish farms effluent in current situation are less than the standard environmental amount, but environmental impacts could be increased by activities of new fish farms,.