Songhua River Basin. According to Tuhua Education Network, Songhua River, located in the northeast, is the largest tributary of Heilongjiang, with a wide drainage area, a large water level drop and a net flow. The basin covers an area of 556,800 square kilometers with an annual runoff of 76.2 billion cubic meters. Songhua River Basin is rich in hydropower resources, concentrated in the main streams of West Songhua River, Nenjiang River and Mudanjiang River, with a total theoretical reserve of 6,598,500 kilowatts, of which the main stream of West Songhua River1398,200 kilowatts, accounting for 2 1.2% of the whole basin.