The evaluation index system of urban aquatic ecosystem health is of great significance for the assessment and management of urban river networks, and for urban development planning. In this paper, the concept of urban aquatic ecosystem health was analyzed by the relationship between human, city and aquatic ecosystem, and its evaluation index system was established from environmental conditions, ecological construction, and social service. In addition, the weight value of each index was calculated by the analytic hierarchy process, and the grading standard of each index was set. Jiading New City, a typical city of the river network plain area in Yangtze River delta, was selected as the aquatic ecosystem health evaluation sample. The fuzzy comprehensive method was used to evaluate the aquatic ecosystem health of Jiading New City. The results indicated that the water ecosystem health of Jiading New City reached the “good” level. For the criterion level, environmental conditions and ecological construction reached the “good” level, and social services reached the “excellent” level. For the indicator level, most indicators reached “good” and “excellent” levels, but the river complexity and benthic macroinvertebrate diversity are still in the “poor” state, which indicates that the aquatic environment has greatly improved, but the aquatic ecosystem has not been fully restored. Results suggested that river complexity and biodiversity should be increased in urban construction planning. The evaluation index system established in this paper can be used to reflect the urban aquatic ecosystem health conditions in river network plain areas.

The plain river network area has a developed economy, a large population, a complex water system, and weak hydrodynamics. In order to improve the hydrodynamic conditions of the plain river network area, clean water sources are introduced through water resources regulation to supplement the ecological water quantity of the river and effectively improve the water environment of the river. In this paper, the Qingsong area in Shanghai is used as the research object. Prototype observation, numerical simulation, and other methods are used to build a hydrodynamic mathematical model of the river network in the Qingsong area, evaluate the water resources regulation effect of the Qingsong area, and put forward two optimization schemes. The results indicate that the overall flow of the Qingsong area is from north to south and west to east, with a maximum flow of 10–68 m³/s in the north–south backbone, exchange cycle between the backbone river, and the peripheral water bodies in the Qingsong area is 4.3 days. The largest amount of water is diverted along the Wusong River, accounting for 53% of the total water diversion; the drainage mainly relies on the gates along the Huangpu River and the Diandong Pumping Gate, accounting for 43% and 42%, respectively. In view of the lowering of the water level in the slice during the low tide period, an optimal regulation scheme has been developed for more diversion and less drainage along the Huangpu River, which can raise the water level in the slice by 0.05–0.10 m. Assessment and optimization of water resources scheduling in the Qingsong area can provide a reference for hydrodynamic enhancement in the river network area of the tidal plain.

One-dimensional modeling of the hydrodynamic river networks of plain urban rivers has been employed to optimize operating regulations in these river networks. However, pilot-scale experiments are still lacking for the validation of hydrodynamics obtained by modeling to improve water quality. In this study, a pilot-scale experiment combined with theoretical calculation was conducted to determine both the hydrodynamics and water quality in the Hutang area of Changzhou, China. The simulation results showed that using high-performance pumps on the border to drain the river beyond it could increase the frequency of water replenishment. The results of the pilot-scale experiment are consistent with the simulation. Moreover, only in condition (c) does the water of the Wuyi canal flow into the Wunan river. With the exception of turbidity, the highest number of rivers with improved water quality tables occurred in this condition. Based on the response mechanism between the flow rate and the water quality, a flow rate within the range of 0.12 m/s to 0.28 m/s can help reduce comprehensive pollution. This study successfully enhanced the hydrodynamic regulation and water quality of the rivers in the Hutang region using technologies combined with simulation and pilot-scale experiments.