Abstract Decadal trends in the concentration of dissolved organic carbon (DOC) in surface water have gained considerable attention due to their significance for aquatic ecology and drinking water quality. Spatial patterns in DOC dynamics hold clues to the causes of DOC variation. Recent developments in digital mapping provide high‐resolution information on soil moisture and how the length of stream networks, including drainage ditches, changes with discharge. This study characterized riparian corridors across multiple flow conditions and spatial extents, showing that although soil moisture became wetter closer to the stream, between‐catchment differences in soil moisture composition were similar across 10, 100 m, and whole‐catchment extents. The study explored how catchment factors influencing spatial and temporal variation in DOC in 145 Swedish watercourses could be explained using high‐resolution spatial data in corridors along stream networks that expand and contract with flow. Catchment‐wide characteristics mapped at coarser scales, combined with meteorological factors and stream flow, explained 64%–77% of observed mean DOC and the influences of seasonality and discharge. Adding high‐resolution soil moisture data and considering them in corridors of different widths did not improve explanation of DOC variation. However, variation in high‐resolution soil moisture contained information important for explaining mean DOC and daily DOC variation. Ditch density and changes in mesic soil moisture class were important for explaining mean DOC, while stream density affected the influence of discharge. Although high‐resolution soil moisture data did not add explanatory power beyond coarser‐scale information, they deepened understanding of how soil moisture and topography influence DOC dynamics.
Lackner et al. (Thu,) studied this question.