Discharge - comparison of measurements (C2, Flowtracker, Flowsens, ADC, tracer, dipping rod)
This page gives an account on the experience gained during a 4-day student course in field-hydrology. Discharge was measured using the Current meter OTT C2, Flowtracker, Flowsens, ADC and the Tracer Dilution method. It is far from being a systematic and conclusive test, nevertheless it gives some impression on trends in usability for untrained personnel.
Settings
- Date: 14. - 17. Sept. 2009
- Location: Selke-stream, downstream Güntersberge, Harz-mountains, Germany, at two similar sections, ca. 7 m apart. Water flow was almost laminar with moderate turbidity, which was sometimes increased by upstream wading. Within the four days, no change in water level was perceived, so discharge must be assumed nearly constant.
- Methods: Each day, a new group of student with only basic background knowledge was introduced to the equipment. Except for days 3 and 4, only 1-point measurements (i.e. 1 velocity measurement per vertical) were performed. The number of verticals varied from 10 to 14 along the sections with ca. 3.5 m width and 0-40 cm water depth. Discharge was also determined by the tracer dilution method, with a pulse injection of 0.5 (Days 1 and 2) and 1 kg of NaCl and measuring electric conductivity as a proxy for concentration.
Results
Comments
The high values of Day 1 result from performing the 1-point measurement being conducted 40 % of the water depth measured from the surface instead of being measured from the ground. Thus, they cannot compared directly to the other days. The values show a bewildering variability (let's blame the students). Except for Day 1, the ADC apparently produces slightly lower values, whereas the Flowsens seems to yield somewhat higher discharge rates. For more conclusive results, the measurements need to be obtained with the identical number of verticals. We'll think about it for the next course.
Links to Wiki-pages of used devices
Discharge - Current meter Ott C2 Discharge - Flowtracker Discharge - Flowsens Discharge - Discharge - Ott ADC