Modelling of Input Phosphate Load to the Caspian Sea from Tajan Watershed Using Soil and Water Assesment Tool

The development of agriculture to respond to growing need for food causes more consumption of chemical fertilizers and water ecosystems pollution. Therefore, in this study estimation of nutrients from non-point sources, the amount of exceed than standard level, evaluation of phosphate pollution input from Tajan watershed to the Caspian Sea is a priority for watershed health assessment.

In this study, the Soil and Water Assessment Tool (SWAT) for the simulation of phosphate during the years from 2001 to 2014 were used.

The results showed that annual phosphate during 2001 to 2014, from about 29,000 to 102,900 kg in watershed output were different. Phosphate in winter and autumn were allocated 98 percent of total annual load. The highest levels of phosphate were in February (an average of 11 621 kg) and lowest in June (average 0.7 kg). Also, phosphate concentration was higher than drinking water quality standards (0.2 mg/l) in most subbasins.  

It is necessary to reduce the phosphatein in these subbasins. They should be prioritized in water quality management programs. Also, results showed that the SWAT model can be a useful tool for pollution reduction strategies.