Figure 1 is here.
Fig. 1 The Gono River and its tributary (Basen and Saijo Rivers), the location of the MLIT gauging stations (Green dots) and the position of the two acoustic stations (T1 & T2) of the FAT system (Red dots).
In addition, Kawanisi et al., (2016, 2018) performed long-term streamflow measurements that was located very close to Ozekiyama station (Fig. 1) using the Fluvial Acoustic Tomography (FAT) system. Hence, as a novel feature for this work, the available hourly discharge records measured by FAT from 2016-01 to 2016-06 was used for further comparison with RC records. Past works had deeply discussed the measurement principles and discharge accuracy by means of the FAT in details (Kawanisi et al. , 2013, 2016, 2018; Razaz et al. , 2013; Bahreinimotlagh et al. , 2016; Al Sawaf and Kawanisi, 2019), thus this work does not aim to repeat the previous works, rather it considers the reliable records of streamflow data as observed by the FAT system for further analysis. However, it is vital to point out that discharge measured by the FAT is computed using the main flow equation in open channels as:
\(Q_{\text{FAT}}=u\ \times\ A\times\tan\theta\) (2)
where u and A are the cross-sectional averaged velocity and oblique cross-sectional area along transmission line, respectively, and θ is the flow angle. As can be seen in Eq (2), unlike the discharge estimated by the RC approach, the discharge computed by FAT comprises both velocity and area (stage) terms.