4. Discussion
Coupling hydrometric measurements such as stage with estimates of
geochemical and microbial connectivity strength is useful for describing
spatiotemporal patterns in connectivity at both target site specific and
river-floodplain system scales. At the target site specific level,
source-target stage relationships reveal patterns of hydrologic response
to both shifting river flows and subsurface groundwater levels. While
high water levels are associated with higher connectivity, source-target
stage relationships are sensitive to both shifts in connectivity type
and the site-level geomorphic controls on water level. However, these
relationships do not necessarily contain information about the type of
connectivity present (surface vs subsurface) without additional
contextual information. For example, in our study both Pond-Con-01 and
Pond-Iso demonstrated similar source-target stage relationships with
Inflow throughout the hydrograph even though Pond-Iso likely had little
to no surface connection with Inflow, whereas Pond-Con-01 did have
surface connectivity. As such, source-target stage relationships did not
reveal differences in surface connectivity between Pond-Con-01 or
Pond-Iso and Inflow. However, our connectivity metrics derived from
geochemical (σg) and microbial (σm)
indicators did identify differences in connectivity between Pond-Con-01
and Pond-Iso and Inflow. Specifically, both σg and
σm revealed low connectivity between Inflow and Pond-Iso
but higher connectivity strength values between Inflow and Pond-Con-01
during high flows, both of which match our visual field observations of
surface water connections. Accordingly, source-target stage
relationships alone did not provide insight to functional connectivity
defined by the observed influence of the source site on the target site,
whereas geochemical and microbial indicators did. Therefore, we focus on
the σg and σm connectivity strength
metrics to describe spatial and temporal patterns of connectivity within
the river-floodplain system.