Geographical location of the Tupalang, Sangardak, and Khalkadjar Rivers ensures synchronized annual flow. High-water and low-water years last up to 4 years. Interchange of low-water and high-water years is different for all three rivers. Taking into account medium altitude of the river basin, high-water year is observed at different times. The earliest flow concentration is observed on the Khalkadjar River, then on the Sangardak, and the latest flow concentration – on the Tupalang River.