Abstract
ABSTRACT The quantification of baseflow is key for water resources management. However, there are few reports on the precision and accuracy in low streamflow measurements. In this paper, we systematically analyze the precision and accuracy of dilution streamflow measurements in headwater channels during baseflow. Precision refers to the variability of the values for repeated measurements and accuracy is how much the measured value approximates the reference one. We measured streamflow in 31 different cross-sections with contributing areas ranging from 0.02 to 5.33 km2. Streamflow measurements with the current meter were adopted as reference for accuracy estimation. A precision error of ±5.0% was found for the measurements. The percent errors compared to reference streamflow ranged from 0.7 to 45.6%, with a median of 6.1%. Precision and accuracy are in the same order of magnitude found in the literature for larger streams. These results can be used for constraining the uncertainty of streamflow measurements and rainfall-runoff modeling of headwater streams.
Highlights
Streamflow from headwater is used for drinking water, irrigation, and recreation (Freeman et al, 2007)
We made a total of 78 streamflow measurements, 12 measurements using the volumetric method (QV) (Table 2), 57 measurements using the dilution method (QD) (Table 3), and 9 measurements using the current meter (QCM) (Table 4)
We found that the dilution was the best measuring method for the cascade morphology which we found in most of our headwaters
Summary
Streamflow from headwater is used for drinking water, irrigation, and recreation (Freeman et al, 2007). Most of the time the water that flows in these streams is baseflow, coming from water stored in the soil and rock profiles (Egusa et al, 2016). There are three main methods to measure streamflow in natural channels: the velocity-area method; the dilution method; and the use of hydraulic structures such as weirs or flumes (Kondolf & Piégay, 2016). The main types of instruments of the current meter are mechanical (rotations of a propeller) or acoustical (ADCP - acoustic Doppler current profiler). It requires a cross-section where the water depth is sufficient for the equipment to work. The dilution method is effective for small streams with irregular channel cross-sections (Bergstrom et al, 2016), its only requirement being that the tracer should be completely mixed with the flow
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