Author(s): Wei Cui, Xiangpeng Mu, Wenxue Chen, Xing Yang
Keywords: Middle Route of the South-to-North Water Diversion Project; Water pollution; Emergency control; Dilution; Constant downstream depth;
Abstract: Three canal pools located along the Middle Route of the South-to-North Water Diversion Project were selected as study areas, and the variation characteristics of water depth, storage, and flow (wave) velocity of sluice-controlled canals with flow rate in constant downstream depth operation were analyzed in this study. The HEC-RAS software platform was used to simulate the transport, diffusion, and dilution characteristics of pollutants when two emergency control schemes—drawing upstream water to dilute pollutants (DUWDP) and intercepting downstream flow to dilute pollutants (IDFDP)—were implemented after emergency water pollution incidents (conservative pollutants) occurred. According to the findings, the average water depth, storage, and dynamic wave velocity of the sluice-controlled canals remained stable at different flow rates. The dilution effect increased along the flow path for both emergency control schemes; the rate of increase was initially rapid and then relatively slow. In both schemes, the dilution effect was optimized at a low initial flow rate rather than at a high initial flow rate. When the initial flow rate remained fixed, the effect in the implementation mode of “high flow rate and short duration” appeared superior to that in the implementation mode of “low flow rate and long duration”. In the same implementation mode, the effect of IDFDP was better than that of DUWDP. There was a point where the dilution became effective in IDFDP; the higher the flow rate, the farther away the effect-onset point. Under the DUWDP condition, the occurrence time of peak concentration was earlier than that with the conditions of natural transport and diffusion. Specifically, the difference between the two peak concentration occurrence times increased initially and then decreased along the flow path. By contrast, under the IDFDP condition, the occurrence time of peak concentration was later than that with natural transport and diffusion; the time difference between these conditions increased along the flow path.