An unusual kind of diurnal streamflow variation

During hydrological research in a Chilean swamp forest, we noted a pattern of higher streamflows close to midday and lower ones close to midnight, the opposite of an evapotranspiration (Et)-driven cycle. We analyzed this diurnal streamflow signal (DSS), which appeared mid-spring (in the growing seas...

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Bibliographic Details
Published in:Journal of Hydrology and Hydromechanics 2018-03, Vol.66 (1), p.32-42
Main Authors: Cuevas, Jaime G, Arumí, José L, Zúñiga-Feest, Alejandra, Little, Christian
Format: Article
Language:English
Subjects:
Evapotranspiration
Forests
Groundwater
Growing season
Headwaters
Hydrologic processes
Hydrologic research
Hydrology
Landscape
Morning
Mountain forests
Mountains
Plantations
Rain
riparian zones
Rivers
Signal delay
Stream discharge
Stream flow
streamflow
Surveying
swamp forests
Swamps
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Summary:During hydrological research in a Chilean swamp forest, we noted a pattern of higher streamflows close to midday and lower ones close to midnight, the opposite of an evapotranspiration (Et)-driven cycle. We analyzed this diurnal streamflow signal (DSS), which appeared mid-spring (in the growing season). The end of this DSS coincided with a sustained rain event in autumn, which deeply affected stream and meteorological variables. A survey along the stream revealed that the DSS maximum and minimum values appeared 6 and 4 hours earlier, respectively, at headwaters located in the mountain forests/ plantations than at the control point in the swamp forest. Et in the swamp forest was higher in the morning and in the late afternoon, but this process could not influence the groundwater stage. Trees in the mountain headwaters reached their maximum Ets in the early morning and/or close to midday. Our results suggest that the DSS is a wave that moves from forests high in the mountains towards lowland areas, where Et is decoupled from the DSS. This signal delay seems to convert the link between streamflow and Et in an apparent, but spurious positive relationship. It also highlights the role of landscape heterogeneity in shaping hydrological processes.
ISSN:0042-790X
1338-4333
0042-790X
DOI:10.1515/johh-2017-0041