Sanjiang or Three rivers plain in Heilongjiang, vast wetland watered by Heilongjiang 黑龍江|黑龙江[Hei1 long2 jiang1] or Amur, Songhua 松花江[Song1 hua1 jiang1], Ussuri 烏蘇里江|乌苏里江[Wu1 su1 li3 jiang1]
Definitions (Wiktionary)
name
Sanjiang Plain (a plain part of the Northeast China Plain, where the Heilong Jiang (Amur), Songhua and Ussuri rivers are confluent in a vast alluvial floodplain in the northeast of Heilongjiang Province)