<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?

Publié en ligne: 26 août 2010

Pages: 149 - 162

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

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

This content is open access.

Are diurnal fluctuations in streamflow real?

Publié en ligne: 26 août 2010

Pages: 149 - 162

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

Mots clésinštrumentálna analýza, metodologické artefakty, južné dažďové pralesy, teploty vzduchu a vody

This content is open access.

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