The water environmental capacity (WEC) in northern rivers has obvious temporal dynamic characteristics because of the seasonal change, so the calculated WEC under a single hydrological designed condition cannot reflect these changes. In this paper, one-dimensional WEC model is used to calculate the pollutant carrying capacity under three different design hydrological conditions of the Yinghe River, which belongs to Yellow River Basin. The results show that: The COD and NH3-N capacity under the staging design condition are increased 7.15% and 9.75% compared with the conventional method; the COD and NH3-N capacity of average monthly flow condition are increased 4.89% and 6.35% compared with the conventional methods; the calculation of the stage design condition is closed to the average monthly flow condition, the COD and NH3-N capacity are increased only 2.14% and 3.20% respectively. Comparing the calculation results under different design hydrological conditions, it is found that the results under the conditions of considering the dynamic characteristics can reflect the actual change law of WEC more accurately and effectively. This research has a guiding significance for realizing the total distribution and seasonal utilization of WEC in the Yinghe River.

Hydraulic restoration in a confined polder river-net is a new issue under the concept of the Interconnected River System Network (IRSN) proposed by the Ministry of Water Resources (MWR) in China. This paper studies the typical hydrographic connection in the polder, and analyses the current situation of the hydrographic river-net in the typical area of Subaiwei in Changshu City by setting up a one-dimensional unsteady hydrodynamic model. The best water diversion-allocation schemes in the confined polder river-net are simulated and optimized in various scheduling rules. In order to recover the ability of hydro-connection and stream function, the effects of different scheduling rules and the duration time of water diversion under the ability of pump stations around polder boundary are compared. The results show that the optimized injects can enhance the total flow velocity and the exchange rate is more than 20% on average in various streams. This study is critical for the sustainable utilization of limited clean water in a confined river-net polder, and for quantifying the water ecological recharge for hydrodynamic connection.