Impact of extreme drought on urban stream temperature regimes

Authors: Iris Stewart-Frey*, Santa Clara University, Meghan Engh, Santa Clara University, Claire Parchem, Santa Clara University
Topics: Water Resources and Hydrology, Geographic Information Science and Systems, Environmental Science
Keywords: hydrology, stream temperature, climate change, drought
Session Type: Paper

Urban streams in highly seasonal, water limited environments, such as exist in California, provide important aquatic and riparian habitat close to population centers, as well as other ecosystem services such as water resources, flood protection, storm water drainage and recreational functions. Yet, water management activities, channel modifications, destruction of riparian zones, and pollution from urban activities often have greatly impacted stream function in urban settings. This has potentially rendered them more vulnerable to more frequent and intense drought periods, such as are projected from climatic changes. Here we compare the stream temperature variability and change between urban and non-urban settings over a period of extreme drought in northern California (2011 - 2016). Hourly stream temperature records from a network of 18 urban stream sites in the urban regions of the southern San Francisco Bay Area represented a variety of stream environments and were compared to non-urban sites and historical records using statistical and GIS analysis. Our results showed that he frequency of occurrence of high stream temperatures and periods of no-flow during drought conditions has significantly increased as compared to historical records and non-urban sites. Stream temperatures stayed significantly cooler at upstream locations that remained solidly shaded. Different stream management options during drought periods may support ecosystem function of urban streams.

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