Study on Suspended Sediment Concentration Measurement in Rivers and Reservoirs

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It is important to know quantity of wash load for the integrated sediment management from upstream through downstream river basins. Generally, both continuous turbidity measuring and bottle sampling are used for suspended-sediment concentration measurement in rivers or reservoirs. However, there is a subject in stability for long time since the turbidity is measured by an optical method and, for bottle sampling, it is very difficult to collect samples without missing at the time of discharge peaks in case for small catchment areas having very short run-off times.This research is to develop a new suspended sediment concentration measuring system with differential pressure transmitter (hereafter, we call SMDP). This method measures suspended sediment concentration by the water density directly with a differential pressure transmitter, without depending on a conventional optical method for the purpose of the solution of such a problem.This method can be applicable for the continuous measurement and the high turbidity measurement. There are two types of SMDP; one is the submersible type and another is the water circulation type. In order to make clear the basic performance of this system, both laboratory and field experiments at the Tenryu river, Miwo dam, and also the Kurobe river have been executed individually.The result that was obtained can be summarized as follows.(1) At the field experiment in the Miwa dam, SS during natural flood flows passing through the reservoir have been measured stably, and the submersible type SMDP can be used for SS monitoring in reservoirs with advantages of real-time and high-suspended sediment measurement.(2) At the field experiment in the Kurobe river, SS during sediment flushing operation from reservoirs have been measured, and the water circulation type SMDP can be used for SS monitoring in natural rivers where enough water depth is hardly secured constantly.