Abstract
In the Kurobe River, coordinated sediment flushing and sediment sluicing of Dashidaira and Unazuki dams have been executed since 2001. From the view point of the comprehensive sediment management in the sediment routing system, monitoring of quantity and quality of sediment transport during these events in rivers and reservoirs is very important. This paper shows the results of continuous measurement of high suspended sediment concentration during sediment flushing and sluicing operation of Unazuki dam in 2015 and 2016. These data have been obtained by submergible type of Suspended Sediment Concentration Measuring System with Differential Pressure Transmitter (hereinafter we call ‘submergible type SMDP’), which is designed to be placed underwater. Measured data have good correlation with manual sampling and effectively utilized to control gate operation by real-time basis during the most critical timing producing extreme high concentration just before free flow starts for sediment flushing.
Highlights
In Japan, comprehensive sediment management in the sediment routing system has been implemented in the Kurobe River and the Tenryu River
This paper shows the results of continuous measurement of high suspended sediment concentration during sediment flushing and sluicing operation of the Unazuki dam in 2015 and 2016 using the Suspended Sediment Concentration Measuring System with Differential Pressure Transmitter (SMDP)
- An underwater SMDP downstream of the Unazuki Dam could measure an extreme high suspended sediment concentration (SSC) up to a peak value of 45,000 mg/l during coordinated sediment flushing in 2016 which is hardly measured by conventional turbidity meter
Summary
In Japan, comprehensive sediment management in the sediment routing system has been implemented in the Kurobe River and the Tenryu River. Sediment management requires measuring the amounts of bed load, suspended load and wash load in a river Conventional techniques such as manual bottle sampling to measure turbidity and suspended sediment (SS) concentration have been conducted to obtain transport rate of wash load and suspended load [1, 2]. We set up a hypothesis that a change in density can be used to measure the SS concentration in river water, and developed SMDP (Suspended Sediment Concentration Measuring System with Differential Pressure Transmitter) equipment. There are two types of SMDPs which are underwater and water circulation ones In the former, the entire measurement system is installed directly in water, while in the latter, river water is taken in by a pump and guided through a pipe to a water tank (a differential pressure sensor is installed inside). In 2015, an underwater-type SMDP was installed downstream of the Unazuki Dam in the Kurobe River (Fig. 1). We overview SMDP measurements and the control trials of the sediment flushing concentration from a dam utilizing SMDP measurements
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