Water environment of irrigation and drainage systems and optimal water control in flat low-lying areas along a coastal zone

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In flat low-lying areas along a coastal zone, the optimal control of irrigation and drainage systems for water-environmental conservation depends on the accurate understanding of flow regimes. During the high water season, a quantitative understanding of flood runoff phenomena is required in particular for optimal control of drainage systems. On the other hand, during the low water season, the physical dynamics of water quality must be considered to maintain good water quality because of the influence of stagnant water and oceanographic phenomena.In this study, we examined the characteristics of flow regime and the physical dynamics of water quality in flat low-lying areas along a coastal zone, and numerical models were obtained to predict optimal water environment and control irrigation and drainage systems.First, Artificial Intelligence models were applied to predict water-stages in a tidal river. It was suggested that Al was an effective technique for the short-term prediction of the boundary conditions that should be used when controlling irrigation aid drainage systems optimallySecond, the transport of dissolved matter in a stagnant body of water was investigated using flume experiments and field observations. It was concluded that the vertical and horizontal transport of dissolved matter was characterized by convection due to the heating and cooling of the water surface aid wind-induced flow The transport of suspended matter in an open channel flow was also investigated with experiments. The transport of suspended matter could be explained in terms of the dynamical structure of shear flow.Finally, based upon the above mentioned results, an expert system for the optimal control of irrigation and drainage systems for water-environmental conservation was successfully constructed using the fuzzy control theory.