From synoptic baseflow campaigns to hydrological processes understanding: a meta-analysis

Synoptic baseflow campaigns use spatially distributed snapshot measurements of discharge and streamwater chemistry to characterize spatial and temporal patterns of baseflow generation across river networks. Despite growing insights from individual studies, transferring process understanding across catchments remains limited by the lack of a comprehensive synthesis. Here, we present a global meta-analysis of synoptic baseflow campaign applications that examine streamflow sources, scaling, and groundwater flow paths. We identified 52 peer-reviewed studies focusing on 71 catchments worldwide. For each catchment, we assessed monitoring approaches and study objectives. We evaluated outcome metrics including Representative Elementary Area (REA) thresholds, baseflow source identification, and the main drivers of groundwater flow paths. Our synthesis shows that synoptic baseflow campaigns have mainly been applied in temperate regions and in small (< 10 km²) to medium-sized (< 100 km²) catchments, with limited representation of arid, tropical, and high-latitude environments. REA analyses from synoptic baseflow campaigns revealed scale-dependent behavior consistent with the fractal organization of hydrological processes, in which the REA, ranging from 0.5 to 75 km², increases with catchment area (ρ = 0.78, p-value = 0.003) and is driven by the aridity index for catchments larger than 20 km² (ρ = −0.90, p-value = 0.037). Geology emerged as a key driver of regional groundwater flow paths, where permeability controls deep groundwater contributions, highlighting the importance of explicitly accounting for geology in hydrological models. Synoptic campaigns are an efficient alternative for investigating hydrological processes in data-scarce regions, supporting the design of long-term monitoring networks, and helping transfer process understanding to ungauged catchments.