Minority View
Throughout history, the cause of flooding on the Yellow River has been the large volume of fine-grained loess, a loamy sediment carried by the wind, from the Loess Plateau on China’s central plain, and continuously deposited into the river, where it collects on the bed. This sedimentation causes natural dams to slowly form over time, obstructions that eventually divert the river, inundating surrounding settlements and agricultural land. These major changes could ultimately cause the river mouth to shift as much as a few hundred kilometers.
The Xiaolangdi Reservoir has regulated sedimentation since 2002 in order to prevent the Yellow River’s bed from rising.
Therefore, for thousands of years, the Yellow River’s frequent changes of course in its lower reaches have resulted in the formation of what is known as a “wide-shift channel.” Historical records indicate over 1,500 instances of devastating flooding before the year 1946, and the river has discernibly shifted course on at least 26 occasions.
In terms of managing the Yellow River, there’s no international historical model that China can refer to. Extremely high sedimentation load and unpredictable morphology make the Yellow River unique, so managing it is among the world’s most complex environmental challenges.
The traditional approach to harnessing the Yellow River is to build high levees parallel to, but a long distance away from, its natural banks, in order to provide a degree of space for the waterway to change its course. However, the construction of a large number of reservoirs along the river, the application of new soil and water conservation practices in the past two decades, and the massive development of new irrigation projects have transformed the riverbed.
In recent decades, based on his personal research into the mechanisms and capacity of the sediment regulation in the Yellow River, Qi Pu and a handful of researchers have put forward an alternative management system to put an end to what Qi views as wasteful and unnecessary practices.
Qi believes that it is unnecessary to widen the lower reaches of the Yellow River to accommodate greater floodplain inundation as a measure to reduce wider flooding. “After the Xiaolangdi Reservoir went into operation in the late 1990s, great changes have taken place in the lower channel, with maximum longitudinal water surface elevation reduced by 10-22 meters, and a dramatic increase in bank discharge. But the wandering reaches are still wide, shallow, scattered and in poor condition, and they need to be regulated on both banks to form a stable, deep and narrow channel,” he said.
Qi told NewsChina that there are successful international examples of “two-bank training strategy” practices, such as projects on the Mississippi River and some other major US waterways.
According to Qi’s son, Qi Honghai, a senior water resources engineer with the global consulting company WSP Parsons Brinckerhoff, the two-bank training strategy can form a narrow and deep channel more suitable for flow discharge and sediment transport. In a recent email exchange with NewsChina, Qi Honghai quoted Dr Dave Rosgen, US expert in river restoration and management, who acknowledged that China should use narrow river channels to facilitate sediment transportation, and to develop stable channels that would prevent riverbeds from rising.
Proper adjustment of the sediment levels of the Xiaolangdi Reservoir could ultimately restore the natural cycle of silt build-up and discharge that occurs during flood periods on the Yellow River, and prevent the main riverbed from rising too high. Meanwhile, if the speed of the main channel’s current can be increased, the flood plain will decrease in size, and debate over constructing new levees can cease. According to Qi and his team, this is the rational method of managing the Yellow River. In 2010, Jiao Yong, vice minister of the Ministry of Water Resources, expressed support for conducting some trial projects on “regulating both banks” along the lower reaches of the Yellow River.
