Lake Hazar is one of the largest and deepest lakes in the Eastern Anatolia Region of Turkey. It is an outstanding natural resource
and famous for its blue, clear, deep and alkaline waters. However, a drastic decrease in water quality and water clarity of the lake
has occured in recent years. This decrease is mainly a result of nutrient and sediment transport to the lake. This study was conducted
to assess water quality of Behrimaz Stream and amounts of freshwater, nutrients, major ions, biological oxygen demand (BOD5),
chemical oxygen demand (COD) and total suspended sediment (TSS) carried by the stream into the lake. It was determined that
the stream had a major impact on water regime, nutrient enrichment and siltation of the lake. Annual water discharge, annual total
nitrogen (TN) and total phosphorus (TP) loads carried into the lake were estimated to be 29×106 m3, 103.77 t and 5.23 t, respectively.
The contribution of TSS load of the Behrimaz Stream to the lake was 24.913×103 t y–1. Over 60% of annual TSS load occured in
April. About 52% of the annual water discharge, 47% of the TN load and 52% of the TP load occured within two months from
March to April. The annual nitrogen and phosphorus loadings to the lake were below permissible loading levels according to
Vollenweider’s criteria.