Weihe river is the biggest river and principal surface water source in Guanzhong Basin.

渭河是关中地区最大的河流，是该地区主要的地表水水源。

youdao

It says the Chinese navy possesses about 75 principal surface combatants, like destroyers and frigates, and around 60 submarines.

WSJ: China Adds Aircraft Carrier to Its Navy

Professor John Zarnecki, principal investigator on Huygens' surface science package (SSP) said the area where Huygens landed appeared to have a thin crust that overlies a material with more uniform consistency something like wet sand.

BBC: NEWS | Science/Nature | Titan mission 'resounding success'

It is on that surface of the ice that they have adapted ways of catching seals that are their principal prey.

CNN: Polar bear now listed as 'threatened' species