Hydrochemical characteristics of a karst basin and its response to world heritage protection

Hydrochemical characteristics in karst areas are crucial for basic water environment research, yet few studies address their response to protected area conservation mechanisms. This study focused on the Huanghou underground river basin, an karst basin of Libo Karst World Natural Heritage Site in China, analyzing 82 water samples. Results show:(1) The basin waters are weakly alkaline with significant ion spatial variation: upstream fluctuations, downstream stability. Ion order: anions HCO₃− > SO42− > Cl− > NO₃−, cations Ca2+ > Mg2+ > K+ > Na⁺. (2)The water chemistry is HCO3-Ca type, mainly dominated by rock weathering: Ca²⁺, Mg²⁺, and HCO3⁻come from carbonate dissolution, while K⁺, Na⁺, Cl−, SO4²−, and NO3− derive from upstream industrial and agricultural inputs. (3) Upstream waters suffer notable human impacts, whereas downstream heritage site waters remain largely undisturbed but face upstream contamination risks. World Heritage water management requires cross-administrative collaboration for a tailored framework. This study provides reference for the management of water resources in World Heritage Sites.