HR: 1330h
AN: H12B-0982    [PDF]
TI: Monitoring Sediment Transport, Stream Stage, and Salinity with Time Domain Reflectometry
AU: * Brainard, J R
EM: jrbrain@sandia.gov
AF: Sandia National Laboratories, P.O. Box 5800 MS 0735, Albuquerque, NM 87185 United States
AU: Tidwell, V C
EM: vctidwe@sandia.gov
AF: Sandia National Laboratories, P.O. Box 5800 MS 0735, Albuquerque, NM 87185 United States
AU: Coplend, A K
EM: accople@sandia.gov
AF: Sandia National Laboratories, P.O. Box 5800 MS 0735, Albuquerque, NM 87185 United States
AB: Preliminary results are presented from an ongoing investigation into the applicability of Time Domain Reflectometry (TDR) for remote, real-time monitoring of streambed dynamics, stream discharge, and water quality. A TDR based stream monitoring system involves propagation of a high frequency, low voltage electromagnetic pulse through waveguides installed riverbed sediments. Reflected signals (traces) from each sensor are analyzed to locate dielectric discontinuities resulting from air-water and water-sediment interfaces, as well as to evaluate the extent of signal attenuation due to the electrical conductivity of the media/water. Trace analysis is by way of a multi-section physical based model using the S11 scatter function and the Cole-Cole parameters for dielectric dispersion and loss (e.g., Feng et al., WRR 35(8), 1999). Application of this approach to data from laboratory experiments demonstrates that TDR can locate air-water and water-sediment interfaces to an accuracy of ñ1.9 mm at a precision of ñ0.4mm. Electrical conductivity of freestanding water above a sediment water interface is measured to ñ8 percent of the actual conductivity at a precision of ñ9 æS/cm. Eight sensors have been installed in the Rio Grande at Albuquerque, New Mexico. Seven sensors capture riverbed dynamics while the eighth is installed adjacent to the riverbank to measure river stage. TDR measurements will be compared to independent measures of riverbed morphology, discharge, and water conductivity.
DE: 1894 Instruments and techniques
SC: Hydrology [H]
MN: 2003 Fall Meeting