The core project concentrates on developing the gullies for agricultural purposes by providing them with protection from floods and an assured water supply for irrigation. This means the construction of a key dam for each gully serving a watershed 3-10 sq km in area. The key dams will be earth dams, made from locally available material, 30-50 m high, and can withstand runoffs from heavy downpours of the 300-year variety even after 20 years of sediment accumulation.
A typical layout for a major core project is shown here for the Niulangou gully which drains into the Kuye River in northern Shaanxi. This is an area of severe erosion with annual erosion rate reaching 30,000 tons per sq km. This site had been developed in the model of a core project for some time, and was to be further developed during China's Eighth 5-year Plan, from 1991-1996. A similar project at Shilichangchuan gully was implemented during the same period of time. It drains into Huangfuchuan River, located also in northern Shaanxi but mostly in Inner Mongolia.
When I was on a project monitoring mission for the World Bank-assisted Watershed Rehabilition Project in the summer of 1995, we inspected project sites just north of the Huangfuchuan River, and in order to see for myself the progress accomplished by the core project, I requested to look at the Huangfuchuan site. The Vice Commissioner of the Yellow River Conservancy Commission, who was also the Project Chief representing the Chinese government in the Watershed Rehabilitation Project, graciously accompanied me on this trip which took an entire day.
On the map, Huangfuchuan did not look too far from Zhungerqi, Inner Mongolia, where we lodged, but the actual travel distance was substantial. They belonged to different watersheds. While the rivers in the Project area in Inner Mongolia flow north into the Yellow River, Huangfuchuan flows southeast into the Yellow River, and the two watersheds are separated by a divide.
We didn't have time to inspect the entire core project at Shilichangchuan, but reached just the northern tip of it. You may see for yourself the condition it was in by looking at some of the pictures I took. They show the transformation of the broad gully floorinto a highly productive region. I also visited a hydrological station and erosion experimentation stationfor this project.
However, gullies with broad floors are rare exceptions (and they usually receive priority in development as in this case), and for the majority cases, the core projects are to be implemented for narrow gullies which are much less productive. It is therefore necessary to demonstrate to decision makers that the increase in productivity for minor gullies will pay for the cost of the core project. I wanted to look at a key dam in one of the branch gullies, but found it too difficult to reach the site, and we were driving on a Toyota Landcruiser. Imagine how difficult it would be to implement such projects without motorized transportation! The transportation issue may account for some of the past reluctance for the government to fund small regional projects, and put undue emphasis on large-dam projects for which access roads can be established. With rapid increase in available motorized vehicles, the logistic issue is totally changed. It should be time to reevaluate the benefits of small regional projects like the implementation of the core projects.
The region in the middle Yellow River basin with annual erosion rates above 5000 tons per sq km extends for an area of 156,000 sq km, which accounts for 83% of the sediment in the main channel. A planning report prepared by the Yellow River Conservancy Commission discloses that within the 156,000 sq km of the heavily eroded area, there are 6758 gullies which are amendable to the construction of key dams, occupying an area of 121,000 sq km. These gullies serve catchment basins of 3 to 300 sq km, and are ideal for the deployment of core projects for gully rehabilitation. Within this area, 18,000 units of key dams may be constructed, controlling an area of 75,600 sq km, which is about half the size of the heavily-eroded area. Once such a program is fully implemented, the sediment load in the river will be reduced by 40-50%.
In a survey conducted on 183 dams constructed during China's 7th Five-year Plan (1986-1990) it is reported that these dams, controlling a combined catchment basin of 956 sq km, cost Y35 million to build. Since the entire loess plateau shows very similar features everywhere, we can use these figures to deduce a unit cost for controlling each sq km of the terrain. At an average construction cost of Y37,000 per sq km of watershed the dams control, we see that protecting 75,600 sq km will cost merely Y2.8 billion, a surprisingly low capital outlay in addressing an issue which is of historic proportion!
Of course,the cost for building such dams at the present time must be elevated due to inflation, and we agree that there might be cost underestimates in the report. For the sake of argument, let us increase the above estimated construction cost by 4 times (close to what I think it should be at 1996 prices) to a total of Y12 billion, it is still substantially less than a single hydro-project like the Xiaolangde dam project, which is targeted for Y20 billion! [I was quoted a cost of Y20 billion in 1994 when I visited the Xiaolangde dam site, but from a recent newspaper article (April 1996) I read the cost had shot up to Y30 billion! (Addendum 1998: In fact the 1996 official price tag for the project was Y35 billion, though in 1997 I heard that the projected cost was already a lot higher.)]
It is important to note that the reason that the key dams can be constructed at such a low cost is because they are earth dams constructed with locally available material by the hydraulic-fill method. The soil in region is very porous and soft, and that is why it is eroded readily by water. On the other hand, one can take full advantage of such a property to facilitate earth-dam construction. Earth extraction is done with water jets, transportation by flow sludge, and compaction by desiccation. Very little mechanical operation is needed, and consequently the construction cost is reduced enormously, making possible such a massive reclamation scheme to be successful.
For China's 9th Five-year Plan (1996-2000) the Yellow River Conservancy Commission proposed to expand the gully rehabilitation program by financing the construction of 500 key dams per year during this 5-year span. Unfortunately, this proposal had not been approved, as I was told last August (1995). If implemented it would set an adequate pace for reclaiming the loess plateau if the proposal is approved. Continued expansion of the program to 1000 key dams per year for the next five-year plan (2001-2005), and to 2000 units for the next (2006-2010), then the above-mentioned 18,000 units of key dams needed to reduce Yellow River's sediment by 40-50% will be achieved within 15 years. It seems like a reasonable target to aim for.
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