The Changjiang sediment flux into the seas: measurability and predictability

Abstract

This paper examines the credibility and predictability of sediment flux of the Changjiang River that has discharged into the seas on the basis of historical database. The assumption of the study stands on the lack of sufficient observation data of suspended sediment concentration (SSC) during peaking flood period, which most likely results in the application of an inappropriate method to the downstream-most Datong hydrological gauging station in the Changjiang basin. This insufficient method (only 30-50 times of SSC observation per year), that obviously did not cover the peaking SSC during peaking floods, would lead to an inaccuracy in estimating the Changjiang sediment load by 4.7×10⁸ t/a (multiyearly) into the seas. Also, sediment depletion that often takes place upstream of the Changjiang basin has, to some extent, lowered the credibility of traditional sediment rating curve that has been used for estimating sediment budget. A newly-established sediment rating curve of the present study is proposed to simulate the sediment flux/load into the seas by using those SSC only under discharge of 60000 m³/s at the Datong station-the threshold to significantly correlate to SSC. Since discharge of 60000-80000 m³/s is often linked to extreme flood events and associated sediment depletion in the basin, un-incorporating SSC of 60000-80000 m³/s into the sediment rating curve will increase the credibility for sediment load estimation. Using this approach of the present study would indicate the sediment load of 3.3×10⁸-6.6×10⁸ t/a to the seas in the past decades. Also, our analytical result shows a lower sediment flux pattern in the 1950 s, but higher pattern in the 1960 s-1980 s, reflecting the changes in land-use in the upstream of Changjiang basin, including widely devastated deforestation during the middle 20th century.

Keywords

sediment rating curve / sediment flux/load / conservation of drainage basin

References

[1] Asselman N E M (1999). Suspended sediment dynamics in a large drainage basin: the River Rhine. Hydrological Processes, 13: 1437–1450

[2] Changjiang Water Resources Commission (1951-1987). Annual Report of Changjinag Water and Sediment (interior report, unpublished, in Chinese)

[3] Changjiang Water Resources Commission (1998). Annual Report of Changjinag Water and Sediment (interior report, unpublished, in Chinese)

[4] Changjiang Water Resources Commission (1999). Atlas of Changjiang Drainage Basin. Beijing: China Map Publisher, 285

[5] Changjiang Water Resources Commission (2001). Atlas of Changjiang Flood Prevention. Beijing: Scientific Publisher, 150

[6] Chen Z, Gupta A, Yin H F (2007). Large monsoon rivers of Asia. Geomorphology (Special Issue), 85 (3-4): 316

[7] Chen Z, Yu L Z, Gupta A (2001). Yangtze River, China. Geomorphology (Special Issue), 41 (2-3): 248

[8] Chen Z J, Liu S Q, Yang D G, Chen G J (2000). Soil and water loss and its controlling countermeasures in the upper reaches of the Changjiang River. Journal of Soil Water Conservation, 4: 1–6

[9] Chinese Water Sediment Bulletin (2004). The Ministry of Water Resources of the People’s Republic of China, 57

[10] Chinese Water Sediment Bulletin (2005). The Ministry of Water Resources of the People’s Republic of China, 73

[11] Chinese Water Sediment Bulletin (2006). The Ministry of Water Resources of the People’s Republic of China, 61

[12] Dai S, Yang S, Gao A, Lu Z, Li P, Li M (2007). Trend of sediment flux of main rivers in China in the past50years, Journal of Sediment Research, 2: 49–58

[13] Fenn C R, Gurnell A M, Beecroft I R (1985). An evaluation of the use of suspended sediment rating curves for the prediction of suspended sediment concentration in a Proglacial stream. Geografiska Annaler, 67A: 71–82

[14] Ferguson R I (1986). River loads underestimated by rating curves. Water Resources Research, 22: 74–76

[15] Gupta A (2008). Large Rivers. New York: John Wiley & Sons, 689

[16] Gupta A, Asher M G (1998). Environment and the Developing World. New York: John Wiley & Sons, 360

[17] Jiang T, Su B D, Heike Hartmann (2007). Temporal and spatial trends of precipitation and river flow in the Yangtze River Basin, 1961-2000. Geomorphology, 85: 143-154

[18] Milliman J D, Syvitski J P M (1992). Geomorphology/tectonic control of sediment discharge to the ocean: the important of small mountainous rivers. Journal of Geology, 100(5): 525–544

[19] Petersen-Overleir A (2004). Accounting for heteroscedasticity in rating curve estimates. Journal of Hydrology, 292(1-4): 173–181

[20] Shi Y F, Jiang T, Wang J, Zhang Q, Su B D, Qin N X (2003). Potential impact of climate warming on the Yangtze floods and estimation of the Yangtze floods based on hypothetical climatic scenarios. Journal of lake sciences, 15: 1–15

[21] Stone R (2008). China’s environmental challenges: Three Gorges Dam: into the unknown. Science, 321(5889): 628–632

[22] Syvitski J P M, Vorosmarty C J, Kettner A J, Green P (2005). Impact of humans on the flux of terrestrial sediment to the global coastal ocean. Science, 308(5720): 376–380

[23] Vansinckle J, Beschta R L (1983). Supply-based models of suspended sediment transport in streams. Water Resource Research, 19: 768–778

[24] Walling D E, Webb B W (1988). The reliability of rating curve estimates of suspended sediment yield; some further comments. In: Bordas M P, Walling D E, eds. Sediment Budgets. Wallingford: IAHS Press, 174: 337–350

[25] Wang H J, Yang Z S, Wang Y, Saito Yoshiki, Liu J P (2008). Reconstruction of sediment flux from the Changjiang (Yangtze River) to the sea since the 1860s, Journal of Hydrology, 349: 318–332

[26] Wang Y J, Jiang T, Shi Y F (2005). Changing trends of climate and runoff over the upper reaches of the Yangtze River in 1961-2000, Journal of Glaciology and Geocryology, 5: 709–714

[27] Xu K, Chen Z, Zhao Y, Wang Z, Zhang J, Hayashi S, Murakami S, Watanabe M (2005). Simulated sediment flux during 1998 big-flood of the Yangtze (Changjiang) River, China. Journal of Hydrology, 313(3-4): 221–233

[28] Yang G F, Chen Z, Yu F L, Wang Z H, Zhao Y W, Wang Z Q (2007). Yangtze River of China, hydromorphological study: sediment rating parameters and implications. Geomorphology, 85(3-4): 166–175

[29] Yang S L, Belkin I M, Belkina A I, Zhao Q Y, Zhu J, Ding P X (2003). Delta response to decline in sediment supply from the Yangtze River: evidence of the recent four decades and expectations for the next half-century. Hydrology, 56: 1–11

[30] Zhang Z X, Zhang Q, Jiang T (2007). Changing features of extreme precipitation in the Yangtze River basin during 1961-2002. Journal of Geographical Sciences, 1: 33–42

Acknowledgements

The authors were indebted to many graduate students of our research group, who contributed to database establishment while studying at the Sedimentological Laboratory, Department of Geography, East China Normal University. The project was funded by Platform of Innovative Research on Water Safety in Estuaries and Coastal Seas (No. 79003A12) and APN project (No. ARCP2008-08CMY).

RIGHTS & PERMISSIONS

2014 Higher Education Press and Springer-Verlag Berlin Heidelberg