Early Warning and Joint Regulation of Water Quantity and Quality in the Daqing River Basin

In the recent decades, the issue of water-resource security of the Daqing River Basin, which is one of the five major rivers in the Haihe River Basin, has become increasingly serious affected by climate change and human activities. In this paper, a dynamic simulation and early warning model of water quantity and quality in this basin based on the SWAT model was constructed to promote the implementation of water environment quality and safety bottom line in the Beijing-Tianjin-Hebei region. The results of the study are as follows: (1) When encountering a once-in-a-century rainstorm, the flood pressure of Zijingguan in the flood season is the highest, with the highest water level reaching 521.23 m, and the overall maximum runoff follows the order of Zijingguan > Fuping > Zhangfang. (2) When the NH3-N emissions are reduced by 37.64 similar to 85.10% in each month (based on the level in 2017), the water quality at the outlet of the basin can reach the standard, and the upper limit of NH3-N emissions is 504.5 t/m. (3) The regulation and control scheme seeking to "ensure the base flow with standard water quality" and "optimize NH3-N annual emission" is proposed in this paper. The NH3-N concentration at the outlet of all watersheds can reach the standard when the basic runoff of each sub-basin reaches 0.01 to 10.32 m(3)/s. In addition, concentrating the emission in July, August, and September and reducing the emission intensity of NH3-N in proportion can significantly reduce the monthly average NH3-N concentration (<1.99 mg/L) at the outlet section of the basin.