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水位計自記紙の記録解像度が流出水量の値に及ぼす影響について [Effect of chart resolution of water-level gauge on runoff values]
Journal article

水位計自記紙の記録解像度が流出水量の値に及ぼす影響について [Effect of chart resolution of water-level gauge on runoff values]

Ikuhiro Hosoda, Wataru Murakami and Roy C Sidle
Journal of Japan Society of Hydrology and Water Resources, Vol.20(6), pp.505-518
2007
DOI: https://doi.org/10.3178/jjshwr.20.505
url
https://doi.org/10.3178/jjshwr.20.505View
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Abstract

Civil Engineering chart resolution aspect ratio shape index long-term observation data quality
The effect of chart resolution (carriage speed and water-level magnification) of a water-level gauge at the outlet of Kamabuchi No.1 experimental watershed on runoff values was examined for a long-term record dating back to 1939. Recent water-level data (original data) were transformed into actual scale coordinates depending on chart resolutions in the past. Then inflection points and hourly coordinates were extracted from the waveforms as transformed water-level data (extracted data) with defined minimum extraction widths and angles. Error was defined as the difference between runoff calculated from the extracted data and the original data, respectively, and was expressed as a percentage of the original data. The effect of chart resolution was very apparent around the peak of the waveform. Since water-level fluctuations are large in the seasons without snow, the range of error becomes larger with lower chart resolution. Unit flood errors increased when the shape index was <0.3. Even if the waveform was carefully traced, maximum unit flood error exceeded 30% in contrast to annual error which was always < 1.2%. Therefore when long-term changes in runoff are analyzed in this study site, it appears possible to use annual runoff data without corrections. However, runoff data of shorter time scales, such as unit flood runoff, should be corrected based on the chart resolution.

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