Maximal Dissolved Matter Discharge of the Amur River

Water floods on the Amur River are quite common and frequently affect vast areas of its basin. Long-term observations near Khabarovsk revealed that significant fluctuations of dissolved matter discharge depend on the flood origin. The maximal dissolved matter flux was proved to coincide with extremely heavy floods, which occur once in 100-150 years. The last one was registered in August 1998 on the Songhua River. At the peak of the flood wave water discharge was 31900 m(3)/s, water mineralization was 85 mg/l and dissolved matter flux was 228 600 t/day. Maximal concentrations of nitrate nitrogen and phosphorus at that time were 0.96 mg N/l and 0.11 mg P/l and their flux in the Amur River was 2687 t/day and 304 t/day, respectively. Much of pollutants came from the intensively fertilized farm lands in China. In 2009, when the Amur water content was increased and the river water discharge was 31 000 m(3)/s, water mineralization was 70 mg/l, and dissolved matter discharge was 175 000 t/day. Nitrate nitrogen flux (1473 t/day) and water content (up to 0.71 mg N/l) was registered as increased. Increased concentrations of nitrate nitrogen registered for a long period prove a substantial flux of this substance in the Amur River (estimated as 48700 t). Phosphorus content 0.019 mg/l and flux 51 t/day are comparatively low. During 2010 floods maximal Amur water mineralization was 120 mg/l, and phosphorus and nitrite nitrogen concentrations were 0.06 mg./l and 1.16 mg N/l respectively. June average dissolved matter flux was 175 320 t/day, much similar to that of the previous years. The flux of nitrate nitrogen (1128 t/day) and phosphorus (57.4 t/day) was rather low. During the extreme floods on the Ussuri River in 2009 much of its valley was flooded (the river water level exceeded 2.0 m of its year fluctuations). Hydrochemical observations revealed low water mineralization (45 mg/l), low concentrations of nitrate nitrogen (0.17 mg/l) and phosphorus (0.024 mg/l), as well as their insignificant flux. Dissolved matter flux of the Amur tributaries (Zeya and Bureya) was fund to be insignificant. The maximal dissolved matter flux, namely that of nitrogen and phosphorus is observed in time of floods formed mostly in the Sungari basin. Floods in the Ussuri basin are found to produce much less negative impacts.