Effects of forest disturbance on water yield and peak flow in low-relief
glaciated catchments assessed with remotely sensed drivers and Bayesian
parameter estimation
Abstract
The catchment approach has been traditionally limited to small,
experimental catchments where water fluxes can be determined with high
accuracy. However, larger catchments where landscape management occurs
have emergent drivers of streamflow at scale, and thus may exhibit novel
responses to land cover disturbance. We used statistical models of water
yield and annual maximum peak streamflow for multiple forested
catchments in the low-relief glaciated region of central North America
to investigate how forest disturbance may affect water yield and peak
flows in similar landscapes. We utilized linear models, linear mixed
effects models, and probabilistic flood-frequency analysis, with
Bayesian parameter estimation in two case studies in Minnesota, USA: 1)
a wildfire comprising ~30% of a 650km
2 wilderness Upper Kawishiwi catchment, and 2) 11
catchments within the St. Louis River Basin ranging from 56 to 8,880 km
2 with a patchwork disturbance regime wherein
~0.25% to 1% of the catchment is harvested or
converted to non-forest land use each year. We also assessed for the
most likely hydrological recovery year after forest disturbance, and the
relative importance of stationary and nonstationary drivers of
streamflow. We found forest disturbance correlated with declines in
water yield for low-level disturbance regimes, but that water yield
increased in response to the large-scale wildfire. Positive and negative
associations of forest disturbance with peak flows were observed,
generally with low confidence. Hydrologic recovery time ranged from 5 to
12 years for water yield and peak flows following disturbance. Despite
these effects of forest disturbance on streamflow, effects of climate
variability and stationary catchment size factors were more prominent
drivers of streamflow. Basins larger than ~50 km
2 in low-relief glaciated regions were resilient to
forest cover change when it comprised <30% of basin area, but
climate change may have a larger effect than could be mitigated by land
management.