Songnen Plain is located in the southwest of Heilongjiang Province, bounded by the Songliao Watershed to the south, the Lesser Khingan Mountains to the north, and the Eastern Mountains and the Greater Khingan Range to the east and west respectively. The entire plain is slightly rhombus-shaped. Heilongjiang Province covers an area of ??103,200 square kilometers, accounting for 21.61% of the total area of ??the province. The Songnen Plain is a depression area in terms of geological structure and is part of the Songliao fault belt. The southwestern part of the depression continues to sink, while the northeastern part is rising. Sediments from the Tertiary and Quaternary periods have risen into platforms, locally called hills. The surface of the Songnen Plain is undulating, so it is also called the wavy plain. The surface of the plain is 120-300 meters above sea level. There are many wetlands and large and small lakes in the central part. The terrain is relatively low. The Nen River and Songhua River flow through the west and south, and the floodplain is wide. The southwestern part of the plain is a closed-flow area, formed by the Wuwei River. On the east bank of the Nen River, there are sand dunes distributed in the Duerbot Mongolian Autonomous County.