Data from: Within-reach temperature heterogeneity is limited in a southern Appalachian stream network, southeastern USA

Stream temperature monitoring networks, combined with geospatial data and
statistical modeling, facilitate temperature mapping at the spatial
resolution of inter-confluence stream reaches and at continental spatial
extents. Comparatively few monitoring efforts quantify spatiotemporal
temperature heterogeneity within inter-confluence stream reaches. We
measured within-reach temperature heterogeneity for six study reaches in a
southern Appalachian stream network, southeastern USA. Within each reach,
we logged temperature at 27 monitoring points every 15 minutes for three
days during early summer and three days during late summer of 2018.
Analysis of variance indicated that daily minimum, mean, and maximum water
temperature metrics vary more among reaches than within reaches. For
example, the difference in daily mean temperature from the warmest to
coldest reach was 8.7°C, whereas within-reach variation never exceeded
2.3°C for any of the three daily temperature metrics. Mixed effects models
indicated that most variation in the three daily water temperature metrics
can be explained by reach-resolution covariates, including elevation,
watershed area, and forest cover. The limited within-reach temperature
heterogeneity was driven by longitudinal position along the reach but,
surprisingly, not by riparian canopy gaps, vertical stratification, or
other factors. Our findings verify that temperature mapping at the
resolution of inter-confluence reaches effectively captures temperature
gradients and indicate that thermally-sensitive organisms have limited
access to fine-scale refuge in southern Appalachian streams. Generally,
within-reach temperature heterogeneity should be quantified in more
geographic and physiographic contexts to understand natural and
anthropogenic drivers of this variation, validate reach-resolution
temperature mapping, and forecast climate change refuges.