Variability of headwater stream network extent is highly sensitive to projected impacts of climate change

Abstract:

Stream networks expand and contract through time, impacting chemical export, aquatic ecosystem habitat, and water quality. Although recent advances improve prediction of the extent of the wetted channel network (L) based on discharge at the catchment outlet (Q), controls on the temporal variability of L remain poorly understood and unquantified. Given that climate change is projected to result in more volatile precipitation, an increased understanding of the stability of L under a more variable Q is needed. Using an analytical framework, we formalize the impact of both the flow regime and stream network hydraulic scaling factors on the relative temporal variability in L. Network hydraulic scaling determines how much L changes for a change in Q, while the flow regime describes how Q changes in time. We compiled datasets of co-located dynamic stream extent mapping and discharge in order to place all globally available empirical data within the model framework. We found that although variability in L is universally dampened relative to variability in Q (i.e., streamflow is relatively more variable in time than network extent), the relationship is elastic, such that headwater catchments will experience greater-than-proportional increases in the variability of L for a given increase in the variability of Q.