Hongze Lake, previously known as Lake Hungtze or Hung-tse, is the fifth-largest freshwater lake in China. Although it is known to have existed from antiquity, it drastically increased in size during the Qing when the Yellow River—then still flowing south of Shandong—merged with the Huai. The increased sediment and flow combined to greatly expand the lake, swallowing the previous regional center of Sizhou and the Ming Zuling tombs. During the imperial and republican periods, the lake formed part of the border between Jiangsu and Anhui provinces but since 1955 the previous borders have been shifted to place it entirely under Jiangsu's administration. It is now encompassed by the counties of Sihong and Siyang in Suqian Prefecture and Xuyi and Hongze in Huai'an Prefecture. Since the establishment of the People's Republic of China, the lake has generally decreased in size as more of its inflow has been diverted for irrigation.