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Shiquanhe is a major city in the northwestern Qinghai–Tibet Plateau. In response to serious problems with windblown sand, sand-control engineering in the Shiquanhe Basin was designed to be implemented in four stages: 1990–1997, 1998–2001, 2002–2004, and 2005–2006. Based on field observations and wind tunnel experiments, gravel sand barriers and tree shelterbelts were designed to serve as the main measures to control windblown sand, with artificial grasslands and irrigation systems also contributing. Parallel 1.2-m-tall gravel sand barriers were set at an angle of 77° to the prevailing wind direction, at a design spacing equal to 10 times the barrier's height (10 H ) in the first and second stages of the implementation and 12 H in the third and fourth stages. But the first stage was never implemented. With the multiple rows of gravel barriers, wind speed reduction below the threshold values is obtained. Tree shelterbelts are arranged parallel to the gravel sand barriers, with local Salix hangongensis the main species. The permeability of the shelterbelts is designed to be between 50% and 80%. Shelterbelts are separated by 43.2 m, close to 14 times of the height of the shelterbelt. Artificial grasslands will be established between the gravel sand barriers and tree shelterbelts. Field investigations in 2002 and meteorological observations show that the second stage of the sand-control engineering has already begun to provide some beneficial effects. |
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