The Asi River’s Estimated Nutrient Load and Effects on the Eastern Mediterranean

Rivers are primary receiving environments for agricultural runoff and for domestic and industrial discharges. Rivers assimilate and treat incoming pollution load until self-purification capacity is reached. The remaining pollution load and natural nutrients are carried to and discharged into the sea causing variations in the receiving area’s nutrient concentration. This study evaluated nutrient loads and effects of the Asi River on the northeastern Mediterranean Sea. Monitoring data from 2006 to 2014 from the State of Hydraulic Works of Turkey were analyzed with an interpolation-based average-estimator model for nutrient load calculation. The nutrient load’s impact on the receiving area was determined using satellite images. Annual nitrite (NO2), nitrate (NO3), ammonium (NH4), and phosphate (o-PO4) loads were found to be 234 102 tones/year, 2 402 066 tones/year, 1 123 714 tones/year, and 603 669 tones/year, respectively, with all nutrients showing distinct seasonality. The Asi River’s load increases during winter and reaches its maximum in spring. High stream flow due to increased precipitation during spring months could explain this situation. Similar results were obtained from satellite images. Chlorophyll-a concentrations in the receiving area increase during winter due to high nutrient load. In other words, nutrient load increases the receiving area’s primary productivity