Analysis for the Relation of Drainage-Waste Ratio and Water Quality Condition of Yangtze River

1. Analysis for the Relation of Drainage-Waste Ratio and Water Quality Condition of Yangtze River Yu Guoan Department of Hydraulic Engineering Tsinghua University

2. Aim of the analysis • To find a general relation of water quality condition of Yangtze River and waste water discharge into the River • Then to forecast a maximum annual waste water discharge to Yangtze River according to water quality requirements

3. contents • Water quality condition of Yangtze River in recent years • Surface water quality standards of China • Drainage-waste ratio (Rdw) and Relation of Rdw andwater quality condition of Yangtze River • Prediction of annual waste water discharge to Yangtze River according to water quality requirements

4. Water quality condition of Yangtze River in recent years • Main stream • part of cross sections of reaches near to the urban areas are polluted • polluted areas mainly including reaches down stream of Panzhihua, a city in South-west China’s Sichuan province, which is about 3600km-long • Tributaries • many tributaries of Yangtze River are polluted at the whole cross section

5. Fig. 1 The Yangtze River Basin and main climate stations and cities along the River • Water pollution condition of Yangtze River reaches along thefive citieswhich are circled by red line in the figure aremore serious

6. Fig. 2 Annual waste water discharge amount to Yangzte River in recent 7 years 27.33 b m3

7. Fig. 3 One of the outlets in Wuhan is discharging waste water into Yangtze River Over 394large-scale waste water outlets are distributed along Yangtze River (Year 2000 data), and waste water discharge has exceeded 27.3 billion m3in 2003. Yangtze River Waste Water

8. mean Fig. 3 Annual runoff of Yangtze River in recent 7 years About 980 b m3

9. Tab.1 Variation trend of water quality of Yangtze River Basin in recent years

10. Surface water quality standard of China • According to “Environmental quality standard for surface water, GB 3838-2002”, surface water quality can be classified into 5 grades (showed in Tab.2): • Grade I-III: fairly good water body • Grade IV-V: generally only used for industrial and agricultural water consumption or for landscape need, belonging to bad water body

11. Tab.2 Water area function and grades classification

12. Drainage-waste ratio Rdw • Rdw: a dimensionless index to reflect the intensity of river flow diluting waste water discharged into it • Rdw can be expressed as:

13. Tab.3 Relation of discharge-waste ratio (Rdw) and Percentage of Grade I-III Water body of Yangtze River in recent 7 years

14. Fig. 4 Correlation of drainage-waste ratio and water quality (Grade I-III) in Yangtze River Discharge-water ratio (Rdw)

15. Prediction of waste water discharge to Yangtze River according to water quality requirements • Prediction function

16. Fig. 5 Rdw Prediction according to Percentage of Grade I-III water body (%) Percentage of Grade I-III water body Discharge-water ratio (Rdw)

17. Prediction results

18. Thank you!