2.5 Metric Evaluation
We evaluated the use of geochemical (σg) and microbial
(σm) connectivity strength metrics using several
approaches. First, we compared σg and σmagainst the conservative tracer (NaCl) injection results including a
binary assessment of arrival or no response of the injected tracer. At
sites with arrival, we calculated Pearson correlation coefficients
between σg and σm and time to peak of
the tracer breakthrough curve (i.e., advective time). To compare
connectivity strength metrics against the relative stage dataset, we
calculated durations of connectivity between source and each target
site. For relative stage, connectivity duration was defined as the
percent of the study period when Inflow stage was above the determined
inflection point in source-target stage relationships as described in
section 2.4. For σg and σm, connectivity
duration was defined as the percent of the study period in which
σg and σm were above 0.5. Pearson
correlation coefficients were calculated to compare whether metrics
performed similarly across all sites. To explore the sensitivity of
results to a chosen connectivity strength threshold, we also calculated
the daily number of connected sites using thresholds ranging from the
10th to 90th percentile of
σm (0.24 to 0.79).