The paper is intended to show the research results about the features of the vertical and longitudinal changes in suspended sediment concentration and longitudinal changes in particle size grading in the reservoir of Sanmenxia on the Yellow River in China and quantitative relationships between point and average concentrations, by using the measured sediment concentration and particle size grading data. First, there are two forms of vertical concentration distributions: one with the concentration increasing from the surface all the way down to the bed bottom and the other with the concentration increasing from the surface to somewhere above the bed bottom where it reaches the maximum. Second, the concentration at the relative flow depth of 0.4 is found equal to the vertical average, just like the velocity at the point equal to the vertical average. Third, concentration and particle size decrease from upstream to downstream in the reservoir when the flow retained is made due to smaller flow releasing capacity of the tunnels while they increase in the period of drawdown. The research findings will be helpful in analyzing sediment distribution and its variations in sediment - Iaden reservoirs, and flushing deposits during the drawdown.
