Potential controls on cold-season river flow behavior in subarctic river basins of Siberia

Results are presented of an inter-basin comparison of cold-season (October–April/March) river flow characteristics for 17 undisturbed catchments in Siberia for the period 1980–1998. Flow and recession metrics for each basin and mean annual cold-season catchment-averaged drainage depth, Qcold (mm), were analyzed with various basin attributes in an attempt to detect potential controls of recession behavior. There is a marked behavioral distinction between basins on non-continuous (n = 6) permafrost coverage (discontinuous/sporadic/isolated) and those on continuous (n = 11) permafrost. The first group is characterized by slow recession, relatively high discharge in April before spring freshet, and high values for Qcold up to about 80 mm, which corresponds to more than 10% of total annual rainfall. Although positive correlations with several catchment attributes (annual precipitation regime; peat land fraction) are found, higher abundance of through-taliks and greater active layer depth (ALD) are presumed to be the most likely controls of the distinctive hydrological behavior of catchments containing non-continuous permafrost. Within the group of catchments on continuous permafrost, characteristics of cold-season flow vary conspicuously as some rivers exhibit very fast recession and cessation of flow for 3–4 months, while others show strongly reduced, but continuous discharge throughout the cold season. Our analysis shows that lake area fraction, peatland fraction and morphological metrics may play a role in favoring prolonged cold-season flow in this group. Whether prolonged cold-season flow in areas of continuous permafrost also signals contributions to river flow from intra- and/or sub-permafrost groundwater remains an intriguing but so far unresolved question.