not-yet-known not-yet-known not-yet-known unknown Tracing Subterranean Flow in Brazilian Neoproterozoic Limestones: Fluorescent Dye Applications in the São Miguel River Basin, Brazil

not-yet-known not-yet-known not-yet-known unknown Karst aquifers are characterized by subsurface circulation through highly heterogeneous and anisotropic conduit networks. Unlike karst provinces developed in Paleozoic and Mesozoic rocks, Neoproterozoic carbonates exhibit very low primary porosity due to recrystallization processes, with groundwater flow predominantly controlled by tertiary (dissolutional) porosity. Despite recent advances with (non-)equilibrium hydrodispersive models, significant gaps remain in understanding the hydrodynamic behavior and in identifying unknown subsurface flow systems. In this study, dye tracer tests (fluorescein, Rhodamine WT, and Tinopal CBS-X) combined with breakthrough curve (BTC) analysis were applied to delineate flow routes, estimate hydrodispersive parameters, and refine conceptual hydrodynamic models of four karst systems (Serra Azul, Vazante, Santo Antônio, and Barra) in the south-central sector of the São Miguel River Basin (SMRB), within the Pains Karst Province (Minas Gerais State, Brazil). Tracer results were integrated with geological-structural, geomorphological, hydrogeological, high-resolution remote sensing, and speleological datasets at basin and sub-basin scales. BTCs revealed strong seasonal variability and heterogeneities such as stagnation zones and temporary storage. Mean velocities ranged from ~26 m/h (dry season, Vazante System) to ~134 m/h (wet season, Barra System). Peclet numbers indicated predominantly advective transport, while Reynolds numbers pointed to flow regimes from laminar to turbulent. Seasonal comparisons confirmed accelerated flow and shorter transit times during high-flow conditions, while low-flow conditions enhanced storage effects within the karst systems. Overall, the newly delineated subsurface routes and BTC-derived parameters demonstrate structurally controlled and hydraulically efficient conduit networks, with rapid connections particularly during the wet season, and highlight the high aquifer vulnerability to contamination. These findings provide a technical basis for local water management and contribute to the integration of karst hydrodynamics at the regional scale. Information & Authors Information Version history Copyright This work is licensed under a Non Exclusive No Reuse License.

Authors Metrics & Citations Metrics Article Usage 134views 68downloads Citations Download citation Gabriel Lourenço, Paulo Galvão, Pedro Assunção, et al. not-yet-known not-yet-known not-yet-known unknown Tracing Subterranean Flow in Brazilian Neoproterozoic Limestones: Fluorescent Dye Applications in the São Miguel River Basin, Brazil. Authorea. 06 October 2025. DOI: https://doi.org/10.22541/au.175978818.89632029/v1 DOI: https://doi.org/10.22541/au.175978818.89632029/v1 If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download. For more information or tips please see 'Downloading to a citation manager' in the Help menu.