Exploring the effect of floodgates operation systems on water environmental capacity in a regulated river network of Wuxi, China

Abstract

For the floodgates operation systems, preventing floods and droughts in a river network for protecting human society based on the safety of the water environment is a challenge. However, researches that focused on the linkage between floodgates operation and water environmental capacity (WEC) is limited. In this study, WEC, as the maximum pollutant load of pollution sources under the requirement of water quality criteria, was estimated and allocated by a combination of a hydrodynamic model, water quality model, and linear programming model before and after floodgates. The results illustrated that WECof chemical oxygen demand (COD) decreased by 4.35% in 2010 and 7.51% in 2018, that of ammonia nitrogen(NH 3 -N) declined by 8.49% in 2010 and 17.73% in 2018 after floodgates were constructed, respectively. The lowest WEC was observed in winter, while the highest one in summer. We inferred that floodgates operation might exert different impacts on WECs in different seasons. Meanwhile, the allowed emissions of COD and NH 3 -N thus were re-allocated in the 15 pollution sources. The amount of pollutants from the surrounding wastewater treatment plants is suggested to be re-set according to the number of population and natural environmental factors. Additionally, the optimal operation of floodgates is needed to improve water quality and water use efficiency. This work can provide basic data and information for the successful management of floodgates operation and effective improvement of water quality in a river network.