We performed water analysis at the water quality measuring points of Gap Stream and Youdenug Stream to examine the water quality impact by the Youdeung Stream inflow to Gap Stream Lake Park due to moving of movable weir. As analytical results, the SS concentration was found to be high during a rainy season, but during a dry season COD and TP concentrations were found to be high. Especially, the TP was higher after the moving of movable weir. From the measuring results of sediments of Gap Stream Lake Park, the concentration of organic matter due to the decrease of flow rate of water was higher than a non-freshwater period, and the downstream concentration of organic matter was found to be higher than the upstream of Lake Park during a fresh water period. The analytical results of water quality for the inflow of Yudeung Stream for maintaining utility water of Daejeon Stream showed no concentration difference according to the points in organic matters and nutrient salts, but the COD and SS concentrations were found to be partially high in the Okgye Bridge outfall. In case of heavy metals they were not mostly detected, so their effects were not high.