Key technical points for integrated surface water-groundwater surveys and assessment in karst basins of South China

ZHOU Changsong; ZOU Shengzhang; LU Haiping; XIA Riyuan; LU Li; WANG Jia; JIQIN Kebuzi; LIN Yongsheng; FAN Lianjie; ZHAO Yi; LI Jun; YANG Yeyu; DENG Rixin; WEI Xianyu; WU Shucheng

doi:10.11932/karst2025y019

Abstract：This study focuses on the karst region of South China,centered in Guizhou Province and encompassing Yunnan,Guangxi,Hunan,Hubei,Sichuan,Chongqing,and Guangdong.The study area covers 780,000 km2 with survey data indicating 520,000 km2 of exposed karst and 260,000 km2 of covered or buried karst.Karst water resources in the region amount to 169.536 billion m3·a-1,representing 83.12％of China's total karst water resources Characterized by a tropical-subtropical monsoon climate-with annual rainfall ranging from 1,000 to 2,200 mm,60％to 80％of which occurs between May and September-the region exhibits complex hydrogeological structures.These include highly heterogeneous aquifers,frequent surface water-groundwater(SW-GW)transformations(with more than 13 types),rapid flow dynamics(conduit flow velocities exceeding 80 m·h-1 during wet seasons),and marked ecological vulnerability. Since the 1970s,with collaborative efforts,the China Geological Survey(CGS)and provincial departments have completed 1∶250,000-scale hydrogeological surveys covering 780,000 km2 and 1∶50,000-scale hydrogeological surveys covering 350,000 km2.Despite the accumulation of extensive data,no integrated technical standards have been established.The 2023 Notice on Carrying out Water Resource Baseline Surveys,issued by the Ministry of Natural Resources,mandates unified investigations of all water bodies.Against this backdrop,this study aims to:(1)systematically define the unique characteristics of water resources and hydrological cycles of the karst areas in Southern China;(2)construct an integrated SW-GW investigation and evaluation framework;(3)identify key technical challenges and propose solutions. Based on four decades of survey data and relevant literature,we systematically synthesized the characteristics of water resources and hydrological cycle.By integrating current standards(e.g.,DD 2019-01,DZ/T 0469-2024)with karst-specific practices,we developed a comprehensive technical workflow.The key results are as follows:(1)Characteristics and Patterns:Seven water resource traits were identified:systemic structural complexity,spatiotemporal heterogeneity of resources,frequent SW-GW exchange,occurrence heterogeneity,hydrochemical erosivity,geomorphological control,and ecological vulnerability.Six hydrological patterns were observed:diverse circulation pathways;close interconnection among atmospheric precipitation,surface water,and groundwater;the high-frequency exchange;rapid flow velocity;multi-layer aquifer connectivity;and coexistence of fast and slow flows.(2)Technical Framework:A six-phase workflow was established:pre-survey planning → field investigation →monitoring → evaluation → database development → reporting.This approach replaces traditional map-based surveys with karst watershed units.(3)Critical Technical Solutions:Unit delineation-Level V karst water systems were designated as core assessment units.Boundary identification-discriminant boundaries were determined based on hydrodynamic fields and geological structures.SW-GW flux quantification-13 transformation subtypes were defined,each with corresponding monitoring strategies.Hydrological process characterization-differentiation was based on the intensity of karst development.Monitoring network optimization-stratified deployment was implemented according to aquifer structure;at least one surface water or groundwater monitoring site per system,with denser coverage at critical exchange nodes(e.g.,sinkholes,spring clusters).Evaluation methods-scale-adapted models,such as Modflow-CFP,were applied for small basins. The integrated framework addresses technical gaps in holistic SW-GW assessment for karst regions in South China,effectively resolving challenges of spatial heterogeneity and dynamic transformations.The six technical pillars-unit delineation,boundary identification,transformation quantification,process characterization,monitoring optimization,and scale-adapted evaluation-provide standardized support for water resource surveys and sustainable management.