Xi made the remarks on Sunday when inspecting a section of the river in south China's Guangxi Zhuang Autonomous Region.
Hailing the river as the only one treasure of its kind in China and the world, Xi said that its ecological environment should never be damaged.
At a dock on the river in Guilin, Xi listened to reports made by local officials on the protection of ecological environment in the river valley, and efforts in cleaning up quarries and illegal sand mining.
The worst part is quarrying, Xi said, adding that if a mountain falls victim to such activities, it will be forever lost.
Should any more excessive sand mining and quarrying take place, relevant parties must be held accountable, and perpetrators investigated for criminal responsibility according to law, stressed Xi.
Earlier "NIA-China" informed that China announces "red" hazard level due to fires.