Abstract
Short-term surges in stream temperature in response to storm events have
frequently been observed in urban areas , highlighting the need
for improved understanding of the factors influencing urban stream
temperature. Urban land cover complexity and infrastructure designed for
rapid water routing to the sewer system create a direct link between
storm events and water release processes, influencing urban stream
temperature responses. This study aims to identify predictors of diverse
stream temperature response patterns to summer storms. We analyzed 403
storm events from six urban and semi-urban catchments along the US East
Coast using dynamic time warping to identify archetype patterns of
stream temperature responses. We further disentangled observed stream
temperature increase patterns to reveal the drivers associated with
“heat pulses”, which are characterized by a rapid but high-magnitude
temperature increase followed by a sharp temperature drop at the start
of the hydrograph. Our results show that stream temperature patterns
were event-specific and linked to pre-event conditions and
rainfall-runoff characteristics, with the shape of the hydrograph and
rainfall-runoff response identified as the most important determinators
of the observed temperature response patterns. Ponded surface waters and
storm drains, as well as cooler water from the shallow subsurface, were
identified as likely sources contributing to temperature patterns. These
findings have important implications for understanding urban hydrology
and the contributions of different source zones in urban catchments.
Specifically, our results suggest that streamwater temperature can serve
as a cost-effective tracer of information about urban water sources and
pathways, aiding in the understanding of complex urban hydrology.