Spatial and temporal dynamics of suspended particles and E. coli in a complex surface-water and karst groundwater system as a basis for an adapted water protection scheme, northern Vietnam [复杂地表水和喀斯特地下水系统中悬浮颗粒和大肠杆菌的时空动态演变–越南北部调整水资源保护方案的基础] [Dynamique spatiale et temporelle des particules en suspension et d’E. Coli dans un système complexe d’eaux de surface et d’eaux souterraines karstiques comme base d’un programme adapté à la protection de l’eau, nord du Vietnam] [Dinâmica espacial e temporal de partículas suspensas e E. coli em um sistema complexo de águas superficial e subterrânea cársticas como base para um esquema adaptado de proteçã o de água, norte do Vietnã] [Dinámica espacial y temporal de partículas en suspensión y E. coli en un complejo sistema de aguas superficiales y subterráneas kársticas como base para un plan adaptativo de protección del agua, norte de Vietnam]

Karst aquifers in subtropical regions are characterized by high variability of water availability and quality due to changes associated with rainy and dry seasons. An additional challenge for water management is the combination of surface-water and karst groundwater systems since high spatiotemporal dynamics cause high variability of water quality. In these cases, adapted protection strategies are required. In this study, a protection approach for the catchment of a river-water diversion point in a rural area in northern Vietnam is developed. The variability of water quality was evaluated by rainy and dry season synoptic surveys of suspended particles and microbial contamination at 49 sites and time series at three sets of paired sites under constant hydraulic conditions. The anthropogenic land-use activities in the catchment were mapped to identify potential contamination sources and to highlight the challenging combination of surface-water and karst groundwater management. The analyzed data indicate differences in water quality between the dry and rainy seasons and a higher influence on water quality from land use than from hydrologic conditions. ... mehrFurthermore, the results suggest a high risk of contamination resulting from residential areas, agriculture, and livestock farming, and reveal the necessity of implementation of appropriate measures such as restricted farming and the hook-up of buildings to municipal sewage disposal. Finally, the data show that water quality can be improved by adjusting water withdrawals by the time of day. The applied methods can be transferred to other surface-water and karst groundwater systems in similar subtropical environments.