Studies on the Hydraulic Structure and Water Qualigy Purification in the Agricultural Channel

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In the study on the hydraulic structure at the agricultural channel, we measured the turbulent flow velocity by the use of the electro-magnetic current meter of the two components. The measurement were conducted over two cases which an aquatic plants are in existence in the agricultural open channel flow and not. By the use of the time series data we calcutated the spectral density function and the curves of R/S.The spectral density function in the region of the high frequency were decreased in the slope of -2.2 at the flow surface and -1.7--1.9 at the flow bottom in the flow shich the aqatic plants were in existence. On the other hand it was -1.66 in the all measurement points of the flow which an aquatic plants were not in existence. From the analysis of R/S, the calcutaion curve was represented by the two lines. Moreover we calculiated the turbulent diffusion coefficients from the auto-correlation coefficeints and the measure of despersion of turbulent velocity.In the study on the purification of the water quality, we conducted two experiments. The first experiment was concered to the self-purification of the water quality. From this experiment we analyzed a suspened solid, dissolved oxygen, biochemical oxygen demand, chemical oxygen demand, total nitrogen and total phosphate over a one week or two weeks period. By the analysis of the water quality, we calculated the removal velocity coefficients of the biochemical oxygen demand and the costants of the reaction speed of the organic nitrogeneous matter from NH_4^+-N to NO_2^--N and from NO_2^--N to NO_3^--N.The second experiment was studied for the artificial purification of the water quality by the use of crushed stone. This apparatus was very effective for the purification of the water quality in the agricultural channel flow.