Effect of cascade dam construction on the spatio-temporal variations of water quality in Heihe River

A comprehensive analysis of impacts of socio-economic development and land use on river water quality in a megacity-region: a case study

“…With a series of implementation projects, such as sewage interception along the river, river restoration, and centralized sewage treatment plants, the main inflow pollution load of the North Canal River in Beijing decreased significantly in 2010 compared to 2007, with COD and NH 3 -N decreasing by 3.08 × 10 4 t/a and 0.17 × 10 4 t/a, respectively (BMEE 2008). The black odor phenomenon of the North Canal River in Beijing was completely eliminated in 2011, and the major water pollutant was shifted from COD to NH 3 -N (Guo et al 2012, Yu et al 2012. In this study, the coefficients of NH 3 -N with each indicator in 2018 ranged from −1 to 1, indicating that the pollution level of NH 3 -N was greatly reduced in 2018 (figure 6).…”

“…In this study, PPI and PSI of the North Canal River basin were decreased from 3.22% and 33.18% in 2010 to 1.23% and 27.33% in 2018, respectively (figure 3). A research report on the North Canal River basin (BMEE 2008) and a 2-year survey of major water pollutants entering the river by our group (Yu et al 2012) found that discharges from domestic, agricultural, and centralized treatment facility were the main pollution pathways in the basin in 2007, accounting for 31%, 35%, and 32% of the total COD emission, respectively. With a series of implementation projects, such as sewage interception along the river, river restoration, and centralized sewage treatment plants, the main inflow pollution load of the North Canal River in Beijing decreased significantly in 2010 compared to 2007, with COD and NH 3 -N decreasing by 3.08 × 10 4 t/a and 0.17 × 10 4 t/a, respectively (BMEE 2008).…”

“…According to this standard, the discharge limits of COD, NH 4 + -N and TP of WWTPs are equal to those of Class IV of (GB 3838-2002). In the North Canal River basin, the Wenyu River, Qing River and Ba River, as the main urban drainage rivers in urban areas of Beijing, the discharge of centralized sewage treatment facilities is its main source of recharge (Yu et al 2012, and the implementation of such upgrade standard has greatly improved the water environment quality of receiving water bodies in the basin and achieved the goal of Beijing's second 'three-year action plan ' in 2018. Areas with better socio-economic development (A2 and A3) have C:N:P ratios of river water quality similar to the effluent from WWTPs (tables 2 and S2).…”