Estimation of Sediment, Organic Carbon, and Phosphorous Loads from Pasikhan River into Anzali Wetland, Iran

Hossein Asadi
The Anzali Wetland, located on the southern coast of the Caspian Sea in northern Iran, is internationally known as a habitat of migratory birds. This is an important area as a spawning and nursery ground for fish, and as a breeding and wintering area for a wide variety of waterfowl. Environmental conditions in the Anzali Wetland have been degraded due to the increased inflow of sewerage, wastewater, and solid waste from industry, agriculture and urban areas. There is also an inflow of sediment from the upper stream mountainous area. This study aims to measure and estimate the total annual OC and phosphorous delivered from Pasikhan River into the Wetland. The estimation of sediment delivery to the Anzali Wetland was updated based on the suspended load measurements in sedimentological stations for nine major entering rivers. Total sediment load was estimated at 683.5 × 103 ton y-1; this shows a significant increase from previous estimations. This indicates that soil erosion is an important problem in the Anzali watershed. Water sampling was performed at Pasikhan River’s Nokhaleh Hydrometric Station, since Pasikhan is considered the most important river entering the Anzali Wetland during one year. The samples were analyzed for phosphorous fractions and organic carbon content of suspended sediment. P concentration and OC showed monthly changes. Both were high in wet months (September to March) and lower in dry months. This pattern also emphasizes the importance of soil erosion on the conditions of the Anzali Wetland. Total OC and P load from Pasikhan River into the Wetland were estimated to be 2710 ton y-1 and 245 ton y-1, respectively.
Eutrophication; Particulate Phosphorous; Soil Erosion; Suspended Sediment
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