Observation site and streamflow dataset description

This research considers the Gōno River which is the largest gravel-bed mountainous river runs through Hiroshima and Shimane prefectures, west of Japan. The watershed of the Gōno River is influenced by cool temperate climate with four obvious seasons: winter (December-February), spring (March-May), summer (June-August), and autumn (September-November). Basically, precipitation happens in winter, however, heavy rainfall occurs in the monsoon (June and July) as well as during typhoon season (August and September). The catchment area of the Gōno River is 3963 km2 and divided into four sub-watersheds, additionally, the Gōno River has two major tributaries namely, the Basin and Saijo Rivers (Fig. 1). The Gōno River watershed is monitored by the MLIT using four real-time gauging stations (Fig. 1) that measure the water stage (H ) directly and discharge (QRC ) indirectly by means of Rating Curve (RC) equations developed empirically using the general quadratic equation as follows (Kawanisi et al. , 2016; Higashino and Stefan, 2019):
\(Q_{\text{RC}}=(c_{1}H+c_{2})^{2}\) (1)
where c1 and c2 are constants, which are empirically computed from calibrations with direct discharge measurements accomplished regularly (Kawanisi et al., 2016). More details about the general features of the sub-watersheds and gauging stations are given in Table 1. Remarkably, the water depth at the river sites turn out to be dramatically shallow under low discharge conditions.