A research on a hydrochemical characteristics of a typical karst basin and its response for world heritage protection: a case study of the Huanghou underground river basin in China

Hydrochemical characteristics in karst area is an important content of basic research on water environment. However, there are few researches on the response of its hydrochemical characteristics to the conservation mechanism of the protected areas, so the Huanghou Underground River Basin, a typical karst basin in the upstream of the Libo Karst World Natural Heritage Site in China was chosen as the study area and 82 water samples were collected and analysed. The results show that: (1) the waters of the basin as a whole are weakly alkaline, the spatial variability of ions is significant, with obvious fluctuations in the upstream and stabilisation in the downstream, and the average values of ion concentrations in each of the four seasons show that the ion concentrations in the upstream are greater than those in the downstream. (2) The water chemistry type is HCO ₃ -Ca type, and the water chemistry composition is mainly controlled by the weathering of rocks; Ca ²⁺ , Mg ²⁺ and HCO ₃ ⁻ in the water body mainly come from the dissolution of carbonate rock weathering, and K ⁺ , Na ⁺ , Cl ⁻ , SO ₄ ²⁻ and NO ₃ ⁻ mainly come from the input with the upstream industrial activities and agricultural surface sources. (3) The upstream water bodies in the study area are significantly impacted by human activities, while the downstream heritage site's water quality remains largely unaffected by major anthropogenic disturbances but faces potential threats from upstream contamination. The conservation and management of World Natural Heritage sites require cross-administrative collaboration to develop a water environmental management framework tailored to the distinctive attributes of World Heritage areas. This study provides reference for the management of water resources in the World Heritage Sites.