Water temperature effect on sand transport by size fraction in the lower Mississippi River

In this study, the effects of water temperature on sediment transport by size fraction are investigated in the Lower Mississippi River.; The following conclusions were obtained: (1) A change in water temperature somewhat changes the vertical velocity profiles and definitely the vertical distribution of suspended sediment concentration; thus, the suspended sediment transport amount in the Lower Mississippi River. On average, a water temperature increase of 1°C causes approximately a 3.49 percent decrease in the suspended sand transport. (2) The average sediment concentration decreases with water temperature regardless of sediment size, but the sand concentration decreases more than the silt and clay concentration with the same range of water temperature change. While, on average, suspended sand concentration decreases by approximately 2.00 percent, suspended silt and clay concentration drops off by only 0.35 percent with a 1°C increase in water temperature. As far as the individual sand fractions are concerned, a change in water temperature influences the fine and very fine sand fractions the most. There is about 2.48 and 1.40 percent decrease in the suspended fine and very fine sand concentration, respectively, with a water temperature rise of 1°C. (3) The reference sediment concentration near the riverbed is also affected by water temperature change. This conclusion mainly results from the analysis of the fine and very fine sand concentrations because the amounts of both the coarse and medium sand near the riverbed are relatively low. (4) Both the calculated and measured Rouse numbers are the same for very fine sand. As the sand size increases however, there is a difference between the calculated and measured Rouse numbers; the calculated Rouse number values being a lot higher than the measured ones for coarse sand. (5) There is a water temperature effect on the flow characteristics, also. Flow velocity and the von Karman parameter decrease slightly with water temperature. While the flow velocity drops off by about 0.66 percent when the water temperature is increased by 1°C, there is approximately a 2.17 percent rise in the von Karman parameter value in the main flow region as a result of the same range of water temperature increase. (6) There is no clear indication of whether the flow direction in the Lower Mississippi River is influenced by the Coriolis force or not. (Abstract shortened by UMI.)...