Application of Strain Gage Technology in Low Flow Stream Monitoring

Streamflow in natural channels is commonly studied for reasons varying from quantifying available water resources to ascertaining the impact of pollution on riparian systems. The accurate knowledge of flow rates with high temporal resolution is particularly important in environmental engineering studies so that mass balances can be determined for geochemical monitoring and modeling. Such studies, as well as beneficial use studies, require an understanding of the stream's hydrological changes on fine scales from minutes to years. However, these studies in low velocity (< 1.5 ft/s) streams are severely limited due to the lack of available flow meter technology. Currently, there is no low cost, portable, low flow meter available. This project involves the design, construction, and testing of two flow meter designs (a surface and subsurface design) which address this deficiency. The meters use strain gage technology to measure the velocity variation across a cross-sectional stream profile. Field and calibration experiments were conducted to determine the best design and also to evaluate the flow meters' accuracy, repeatability, usability, and range. The study found that the surface velocity meter design was much easier to use, but the subsurface design, which measured velocity at various depths, was considered to have better repeatability and accuracy. The results of this study show flow meters based on strain gage technology may provide an inexpensive, accurate and simple means to monitor flow rates in low velocity streams.Air Force Inst of Tech Wright-Patterson AFB OH is the author of 'Application of Strain Gage Technology in Low Flow Stream Monitoring', published 2000 under ISBN 9781423537632 and ISBN 1423537637.