Author(s): H. Yokoyama; K. Sugihara; K. Watanabe; H. Yabe; M. Hashiba
Linked Author(s): Hiroshi Yokoyama
Keywords: Component; High turbidity; ADCP; Echo intensity; Sonar equation
Abstract: We aim to develop observation method of space-time distribution of turbidity in dam reservoir where high turbidity has been confirmed over long period. Movement of high turbidity may affect water intake from dam. So we need to monitor space-time change of turbidity and flow simultaneously in dam reservoir. However, it is very difficult to get space-time distribution of turbidity by standard monitoring method, such as water sampling or measurements by turbidity meter. Turbidity estimation from echo intensity of ultrasonic wave of acoustic Doppler current profilers (ADCP) is appropriate methods to get space-time distribution of turbidity and flow. We aim to apply this method for monitoring of turbidity in the dam reservoir. We checked accuracy of turbidity estimation of this method. Towing observations of ADCP were conducted after floods under high turbidity. First, we checked characteristics of echo intensity of ADCP, which is the base data of turbidity estimation. We confirmed that echo intensity of ADCP was attenuated depending on turbidity concentration. So we set attenuation coefficient by water depending on turbidity. Next, we compared estimated turbidity from echo intensity of ADCP and observed turbidity by turbidity meter in some points in the reservoir. Estimated turbidity was adapted to observed value less than 1500ppm. So we could get good accuracy under high turbidity caused by floods. On the other hand, accuracy of estimated turbidity was not good in observation point which was near inflow rivers in some floods. It suggested that accuracy of estimated turbidity of ADCP was affected by characteristics of suspended materials.
Year: 2014