<abstract xml:lang="en" xmlns="http://www.w3.org/1999/xhtml"><p>Diurnal variations in streamflow (DVS) have been studied in detail by underwater pressure loggers. Some of this equipment requires barometric compensation with a logger or sensor located outside the water. Studies related to this topic have not offered a critical report of the validity of patterns inferred with these instruments. While studying a forested watershed in Southern Chile (40° S), we detected a DVS when the external logger was placed 1.5 m above ground, under a marked diurnal fluctuation in air temperature (amplitude 12.4 °C) and a dampened fluctuation in stream temperature (amplitude 1.4 °C). Synchronization was apparent between air and stream temperature in a direct relationship, but the synchronization between air/stream temperature and streamflow was negative, with some hours of lag time. In laboratory experiments, when the external logger is considerably warmer than the water-level logger, depth measurements can be underestimated by up to 1.5 cm. When the opposite occurs, water depths can be overestimated by up to 0.9 cm and are large instrumental/methodological artifacts compared to the field water diurnal variation of 1.3 cm. Finally, we relocated the external logger in front of the water-level logger and inside a weir, but exposed to the air. Results confirmed the pattern previously detected in the field, but streamflow fluctuations were 19% less accentuated. We conclude that the incorrect placement of the external logger, along with an instrumental artifact, can intensify a DVS pattern.</p></abstract>

Diurnal variations in streamflow (DVS) have been studied in detail by underwater pressure loggers. Some of this equipment requires barometric compensation with a logger or sensor located outside the water. Studies related to this topic have not offered a critical report of the validity of patterns inferred with these instruments. While studying a forested watershed in Southern Chile (40° S), we detected a DVS when the external logger was placed 1.5 m above ground, under a marked diurnal fluctuation in air temperature (amplitude 12.4 °C) and a dampened fluctuation in stream temperature (amplitude 1.4 °C). Synchronization was apparent between air and stream temperature in a direct relationship, but the synchronization between air/stream temperature and streamflow was negative, with some hours of lag time. In laboratory experiments, when the external logger is considerably warmer than the water-level logger, depth measurements can be underestimated by up to 1.5 cm. When the opposite occurs, water depths can be overestimated by up to 0.9 cm and are large instrumental/methodological artifacts compared to the field water diurnal variation of 1.3 cm. Finally, we relocated the external logger in front of the water-level logger and inside a weir, but exposed to the air. Results confirmed the pattern previously detected in the field, but streamflow fluctuations were 19% less accentuated. We conclude that the incorrect placement of the external logger, along with an instrumental artifact, can intensify a DVS pattern.

Are diurnal fluctuations in streamflow real?

Instituto de Investigaciones Agropecuarias, Oficina Técnica Valdivia, Campus Isla Teja s/n, Casilla 567, Valdivia, Chile

Instituto de Geociencias, Universidad Austral de Chile, Campus Isla Teja s/n, Valdivia, Chile

Escuela de Graduados, Facultad de Ciencias Forestales y Recursos Naturales, Universidad Austral de Chile, Campus Isla Teja s/n, Valdivia, Chile

Fundación Centro de los Bosques Nativos, FORECOS, Chile

Journal of Hydrology and Hydromechanics

{"article-title":"Are diurnal fluctuations in streamflow real?"}

Diurnal variations in streamflow (DVS) have been studied in detail by underwater pressure loggers. Some of this equipment requires barometric compensation with...

Are diurnal fluctuations in streamflow real?

Published Online: Aug 26, 2010

Page range: 149 - 162

DOI: https://doi.org/10.2478/v10098-010-0014-0

Keywords
inštrumentálna analýza, metodologické artefakty, južné dažďové pralesy, teploty vzduchu a vody

This content is open access.

Are diurnal fluctuations in streamflow real?

Published Online: Aug 26, 2010

Page range: 149 - 162

DOI: https://doi.org/10.2478/v10098-010-0014-0

Keywordsinštrumentálna analýza, metodologické artefakty, južné dažďové pralesy, teploty vzduchu a vody

This content is open access.

Keywords
inštrumentálna analýza, metodologické artefakty, južné dažďové pralesy, teploty vzduchu a vody