I was asked by Mr. Qi Pu for his a new published collaborators’ research monograph to write this Preface. The book contains their long-term research results of the sediment problems in the Yellow River. I did it late because I do not feel to have the floor on the book due to that I am little known about the Yellow River circumstance, and in a layman especially on the sediment dynamics and the problem of sediment transport. After considering for a long time, I hold a pen and write the following words, this is a preamble, rather some feelings. I write out it for authors and experts to be referred and commented on.
The Yellow River is the China’s mother river , and the Yellow River basin is the cradle of Chinese civilization. Beyond the memory of men and throughout the history, floods and drought disasters in the Yellow River basin are very frequent and serious, especially due to that the sediment concentration in the river is huge, the downstream river bed silts up unceasingly, the river becomes the suspended river higher than its banks, and the river bank bursts durring large floods, causing the vast area to be flooded, even river diversion maks disaster-ridden, therefore the Yellow River is also called China's misery, and is rivers which in the world is most difficult to be governed with. Since 1949, although the harnesing of the Yellow River has made great achievements, but did not solve the problem of sediment ultimately, the river bed is continuously siltted up, forming a second-order-suspended river. After completion of the Xiaolangdi Multipurpose Dam project, very good results have been achieved via the reservoir regulation of water and sediment dischage to scour the sediment in the reservoir and its lower river channels. But how to optimize the operation of water and sediment discharge and make the most favorable effect of washing sediment deposition, it relates to the harnesing orientation of the lower Yellow River and still has all sorts of disputes.
The key research project by the authors to work with perseverance for 30 years is emphases on how to use the hyperconcentration flood flow larger than 3000m3/s to transport the sediment into the sea, enable the sediment in downstream river channels basically to achieve the equilibrium of sediment erosion and deporsition. This possibility exists according to the authors’ comparative analysis of measured data and their summarization of the river sediment transport law, the premise is to create a stable downstream of narrow-deep river channel, and optimize a mode of water-sediment regulation in Xiaolangdi Reservoir to release an artificial flood, carry out overyear regulation of sediment, change incoming water and sediment composition of the lower river channels, which enable to suit the longe distance flowing condition of hyperconcentration flow, thereby the flood can be fully used to discharge the sediment. If those could be achieved, the major part of sediment would be transported entering the sea, to create a balanced condition of sediment erosion and deposition in the lower river channels. From this understanding, the authors propose the different opinion to the current harnessing theory and practice of the Yellow River.
If the author's scenario can be achieved, of course, it is very good: the lower Yellow River channels can no longer be silted up, the Xiaolangdi Reservoir can bring into play in long term (instead of trapping), and also the floodplain can be released due to that it do not have to rely on both sides of the floodplain used for silting. Because of the complexity of problems and influencing severity, the author's research results and the corresponding harnesing programmes exist in different point of views, and this is understandable. Science progress constantly in discussions and debates, the truth is radicated under the continuous research, testing and in practice. However, no matter what scenario is adopted, it is consistent that a stable and deep river channel would be wanted to be created in the lower River reaches, and is always right that the orientation of to deep study it and give fully play to its sedment transport potential. The book published will facilitate debates. I hope the people of all circles concerned the Yellow River harnesing, especially the colleague who research sediment transport law of the Yellow River can discuss the viewpoints and conclusions of the book, and also the authors being calm and even-tempered to deal with various discussions and oppugned opinons, deepening and improving their work, and to reach a consensus, for the realization of the Yellow River's ultimate goal to make more contributions.
In addition, for the deeping research on harnessing of the lower Yellow River reaches, I thought that also has several major problems to be worth further discussing:
1. In history, flood disasters in the lower Yellow River reaches were very serious, but large floods here have not happened in recent decades due to various reasons, even in the flood seasons the larger flood peaks are also not to be formed. How the defence standard for the lower Yellow River flood from now on is determined in reason? Can the defence flood discharge be cut down largely? How to deal with the above-norm flood when meets? These problems must have clear conclusions approved by the State, as the objectives and warranty of the Yellow River harnessing.
2. After a variety of harnessing measures (including the author's programme) to be adopted, how to secure a reasonable and reliable estimate of the annual sediment deposition quantity in the lower river channels in the near future? When can anticipatorily the sediment erosion and deposition equilibrium be completely reached? Meantime what are the gross sediment deposit amount and siltation shape in downstream river course? What is the impact of the flood control? How is the reliability of that the authors believe that their harnessing programme to be adopted can maintain the river channel to be not deposited? How much room should be left? Whether should the sediment deposition and flood discharge function of the floodplain be reserved?
3. The Yellow River emptys itself into the Bohai Sea that is a shallow sea, sediment discharged out of the river mouth can not automatically entering the deep sea area, and it appears as the continuous extension of the Delta and smoothout of the riverbed slope, as a consequence those have a gradual impact of sediment transport into the sea. How to recognize in macroscopic way and specific solution to this problem seems to be doing more in-depth research (see Chapter 16 of the book).
4. The harnessing orientation of the lower Yellow River relates the 1,800,000 farmer's development direction who depend upon more than 3,000,000 Chinese acres of floodplain by both banks for making a living. this is currently the most real problems on the lower Yellow River harnessing. If the author's suggestion was accepted, farmers housing on the floodpains within both banks would enjoy a good and prosperous life gradually. If according to the current river harnessing planning to put into practice, a early planning would be needed to do that how to scientifically and rationally use the floodplains in both banks, and whether or not the resident on the floodplain to be requalification or change the position. In the river harnessing opinion can not be temporarily in the consistent situation, to shape a stable and deep river channel in the downstream river reaches is a scenario of compromising all sorts of assumption and advantageous exploration step by step. Meanwhile, the operation mode for water and sediment regulation of the Xiaolangdi Reservoir may be explored and optimized, to closely monitor the sediment deposition reduction of the lower river channels, to see that whether the river bed sedimentation can be controlled or not, and whether the river channels’ flood dicharging capacity can be increased unceasingly or not, then to decide what river harnessing scheme can be adopted, it seems a positive and safe way.
Certainly, these questions do not belong to the research scope of this book, I just like to take this opportunity to put forward for leaderships and observant and conscientious persons to be taken into account.
Above is my preface for authors and readers to refer to and comment.
Pan Jiazheng
on June 17, 2010
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