Effects on water quality after water transfer in the Yinxi Watershed, Ningbo, China

With the development of economy and society, water transfer has become an important measure to improve water quality because of its low cost and easy operation. To reduce the negative impacts of sudden water pollution in the Yinxi Watershed, Ningbo, a series of experimental water transfers were conducted. The water quality indicators (chemical oxygen demand, free ammonia nitrogen, and total phosphorus) were analyzed to determine changes in pollutant concentration. The results show that water transfer is an effective measure to improve the water quality but the water quality showed temporal and spatial heterogeneity. To improve the water quality of the Yinxi watershed, the inflow rate of Gaoqiao pumping station and Hongshuiwan check-gate should be 13.44 m3/s and 120,000 m3/d, respectively, and some sluices should be opened to drain water and effectively improve water flow and quality in the whole region. Besides, a 2 d frequency of transfer is needed to improve water quality, and the optimal pattern of transfer is diverting after draining. On the basis, the management of regional water resources to improve water quality is proposed. These experimental transfers help to better understand the effects of water transfer on regional water quality, formulate and implement effective water resources management, and provide references for similar watersheds.