Evapotranspiration and groundwater inputs control the timing of diel cycling of stream drying during low-flow periods

Authors: WARIX, SARA - Idaho State University; GODSEY, SARAH - Idaho State University; Flerchinger, Gerald; Havens, Scott; LOHSE, KATHLEEN - Idaho State University; BOTTENBERG, H - Idaho State University; CHU, XIAOSHENG - Northwest Agricultural & Forestry University; HALE, REBECCA - Idaho State University; Seyfried, Mark

Submitted to: Frontiers in Water
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/3/2023
Publication Date: 10/25/2023
Citation: Warix, S., Godsey, S., Flerchinger, G.N., Havens, S.C., Lohse, K., Bottenberg, H.C., Chu, X., Hale, R., Seyfried, M.S. 2023. Evapotranspiration and groundwater inputs control the timing of diel cycling of stream drying during low-flow periods. Frontiers in Water. 5. Article 1279838. https://doi.org/10.3389/frwa.2023.1279838.
DOI: https://doi.org/10.3389/frwa.2023.1279838

Interpretive Summary: In the western United States, precipitation is scarce during the hot summer and headwater streams can dry. We monitored stream drying patterns at 25 locations in a headwater stream in Idaho’s mountains during summer 2019. At most locations, in the days immediately preceding seasonal stream drying, we observed fluctuations in surface flow so that the stream was flowing at night and dry during the day. We found that during low-flow periods, stream drying usually started when evapotranspiration losses peaked and exceeded the amount of groundwater contributing to surface flows. Using measurements of vegetation greenness from fine-resolution (3 m) satellite images, we found that vegetation was greenest when the stream was flowing and least green when the stream was dry, suggesting that satellite greenness patterns may be useful to predict future stream drying. We conclude that evapotranspiration losses are closely coupled with the timing of stream drying.

Technical Abstract: Geologic, geomorphic, and climatic factors have been hypothesized to influence stream drying patterns, but hydrologists struggle to explain the spatiotemporal patterns of drying. Few hydrologists have isolated the role that vegetation plays in controlling the timing and location of stream drying. We present a distributed, fine-scale water balance through the seasonal recession and onset of stream drying by combining spatiotemporal observations of flow presence/absence, evapotranspiration, and baseflow inputs. In addition, we compare high-frequency, fine-resolution riparian normalized vegetation difference index (NDVI) with stream flow status. We found that the stream wetted and dried on a daily basis before seasonally drying, and daily drying occurred when evapotranspiration losses exceeded baseflow inputs, typically during the hours of peak evapotranspiration. Riparian NDVI decreased when the stream dried, with a ~2-week lag between stream drying and response. Stream diel drying cycles reflect the groundwater and evapotranspiration balance, and riparian NDVI may improve stream drying predictions.