Study on Maintenance of Water Quality in a Fishpond through Water Diversion

Water quality maintenance is always a focus in a fishpond in order to achieve a high harvest and good scenery. A wetland fishpond in Yingdong Village on Chongming Island, Shanghai has been studied. Through a 2D modeling analysis it is found that the water diversion from the neighboring Yangtze River is feasible and effective. The diversion can be conducted once every 2 months to achieve the desirable water quality in the fishpond with NH4-N concentration below 0.5 mg·L-1. However the modeling results show that there are 4 regions in the fishpond where the water can not be exchanged via water diversion owing to the specific topographic condition. It is suggested that in these areas shallow water wetland should be designed in order to maintain good water quality and meanwhile generate delightful scenery. Moreover, a pretank system has been proposed at the intake and outlet of the fishpond to purify the inflow from the Yangtze River and outflow back to the River.