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Check Dam in the Loess Plateau of China: Engineering for Environmental Services and Food Security. Yafeng Wang,*,† Bojie Fu,† Liding Chen,† Yihe L€u,† and Yang Gao‡ †
State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, CAS, Beijing 100085, P. R. China ‡ Key Laboratory of Water Cycle and Related Land Surface Processes, Institute of Geographic Sciences and Natural Resources Research, CAS, Beijing 100101, P. R. China
Figure 1. The amount of check dam in seven provinces of Loess Plateau.
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n the world, dams and reservoirs are often controversial projects because of their social and environmental impacts, in addition to the high cost of construction and river diversion. But in Loess Plateau, check dams have attractive advantages because of unique environmental settings and regional food supply needs. Check dams are the most widespread structures for conserving soil and water in the Loess Plateau. The Loess Plateau covers an area of some 640 000 km2 in the upper and middle reaches of the China’s Yellow River. Over 60% of the land is susceptible to soil and water losses and the soil of this region has been called the “most highly erodible soil on earth”.1 Constructing check dams in the gullies is an effective strategy for reducing sediment loss. More than 100 000 check dams have been built over the last 50 years in the Loess Plateau.2 After 50 years of construction, there are about 110 thousand check dams storing 21 billion m3 sediments in the Loess Plateau. The check dams distribute mainly in seven provinces including Shaanxi (36 816), Shanxi (37 820), Gansu (6630), Inner Mongolia (17 819), Ningxia (4936), Qinghai (3877), and Henan (4147) which account for 82.5% of the total 2 (Figure 1). It is highly significant that the check dams curb sediments from flowing into the Yellow River at a rate about 3 5 million tons r 2011 American Chemical Society
annually, and they have intercepted 28 billion tons sediment since 1950s in the Loess Plateau.2 Generally, a small watershed is used as a planning and construction unit for check dams. They are constructed step by step from downstream to upstream; the combination of large, medium, and small dams can effectively mitigate flood damage and sedimentation downstream. The check dams can essentially raise the base level of the controlled watershed and thus reduce gully and headward erosion. The check dams can potentially serve as carbon storage and sequestration structures. The average organic carbon content in sediment trapped by check dams is 3.4 g kg 1. If estimated at this rate, the carbon storage in check dams of the Loess Plateau can amount to 0.952 Gt (1Gt = 109 t = 1015 g), which amounts to 18 24% of the total carbon storage of forest vegetation in China.3 The existing reseach results indicated that carbon sequestration was 2.3 Tg (1 Tg = 1012 g) in the new plantations in the upper Yellow River Basin from 1998 to 2004.4 Therefore, we indicated Received: November 2, 2011 Accepted: November 8, 2011 Published: November 16, 2011 10298
dx.doi.org/10.1021/es2038992 | Environ. Sci. Technol. 2011, 45, 10298–10299
Environmental Science & Technology that the carbon sequestration is more than 400 times by the check dam than by the new plantations under the “Grain to Green” program in the Loess Plateau. Otherwise, this carbon will be transported to the Yellow River and carbon release to the atmosphere is inevitable during the transport process in the water environment to potentially contribute to global warming. When check dams are filled up with sediments, man-made plain lands come into being and can be reclaimed as high quality croplands because of the nutrient enrichment during soil erosion processes on hillslopes and improved water availability. By 2002, 3200 km2 of dam croplands had been created.2 According to the monitoring data from the Suide Soil and Water Conservation Experiment Station of the Yellow River Conservancy Commission, the soil water content in dam cropland is 1.86 times of that in slope cropland. The food production in dam cropland is 2 3 times higher than that in terrace cropland, and 6 10 times higher than that in slope cropland. The average yield is 45 000 kg ha 1 with some even up to 105 000 kg ha 1. Accordingly, dam cropland accounts for about 9% of the total cropland area in the Loess Plateau, whereas the food production amounts to 20.5% of the total food production.2 With the productive dam cropland, farmers can grow high profit crops or developing fresh water aquaculture to raise family income. Therefore, farmers’ dependence on slope farming is largely reduced, which has facilitated the effective implementation of the large scale vegetation restoration program known as Grain to Green that is motivated by the Chinese central government and recognized as the world's largest payment for ecosystem service initiative.4 The results indicated that the vegetation restoration efforts had significantly improved land coverage grass, scrub, and woods resulting in an effective control of soil erosion.5 Accordingly, the check dam as a hydro-engineering approach for soil erosion control has actually brought about services for environmental conservation and human welfare in the Loess Plateau of China. To sustain these benefits of check dams, participatory approach and adaptive management is required for planning, construction, use, and maintenance of the anthropogenic structure. The case of check dams in the Loess Plateau region verified the possibility toward building harmonious relationships between man and nature by well designed engineering systems. Therefore, ecologically and environmentally friendly design is promising to adapt to a changing world.
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(2) CMWR (Ministry of Water Resource of P.R. China). Programming for check dams in the Loess Plateau (Technical Report), 2003; pp 47 48. (In Chinese) (3) Zhao, M; Zhou, G. S. Carbon storage of forest vegetation in china and its relationship with climatic factors. Climate Change 2006, 74, 175–189. (4) Liu J, et al. Ecosystem Services Special Feature: Ecological and socioeconomic effects of China’s policies for ecosystem services. Proc. Natl. Acad. Sci. U.S.A. 2008, 105, 9477-9482. (5) Fu, B. J.; Chen, L. D.; Ma, K. M.; Zhou, H. F.; Wang, J. The relationships between land use and soil conditions in the hilly area of the Loess Plateau in northern Shannxi, China. Catena. 2000, 1, 69–78.
’ AUTHOR INFORMATION Corresponding Author
*Phone: 86-10-62849102; fax: 86-10-62849102; e-mail: yfwang@ rcees.ac.cn.
’ ACKNOWLEDGMENT This work was supported by the National Natural Science Foundation of China (No. 40901098) and the Knowledge Innovation Program of the Chinese Academy of Sciences (No. KZCX2-YW-QN408). We thank Geoffrey Hart (Montreal, Canada) for editing an early version of this paper. We are also grateful for the comments and criticisms of the journal’s anonymous reviewers and my colleagues. ’ REFERENCES (1) Laflen, J. M., Tian, J. L., Huang, C. H. Soil Erosion and Dryland Farming; CRC press: Boca Raton, FL, 2000; p 736. 10299
dx.doi.org/10.1021/es2038992 |Environ. Sci. Technol. 2011, 45, 10298–10299
