The delta of the Yellow River, China's second longest waterway, is shrinking southward by an average 7.2 square kilometers a year due to seawater erosion, a geological survey found.

The delta in the northern part of the eastern Shandong Province, where the Yellow River empties into the Bohai Sea, used to claim 22 sq km of land annually from the sea before 1996, said Xu Junxiang, a surveyor with the Shandong provincial geology and mineral bureau.

Sand that drifted to the delta with seawater has fallen below the soil cutback during the past nine straight years. This has happened particularly along the coastline in the northern border of the delta in Dongying, Xu and his colleagues have found after site surveys and analysis of satellite pictures captured during the past three decades.

Xu acknowledged that the Yellow River Delta is losing some of its newly accrued soil to the sea again as a result of decrease in the river water flow and weathering of the seawater.

Historical data show the delta has claimed altogether 230 sq km of land since 1855 and it presently covers 650 sq km.