Jul 26, 2016 - network, and water conservancy projects in the Yellow River basin, North ... average elevation of over 4000 m, the mountain region has an ...
Chapter
101
Yellow River Basin BY
JI CHEN, HAIYUN SHI, LIQUN SUN, AND JUN NIU
ABSTRACT
This chapter introduces the profile, climate, hydrology, observation station network, and water conservancy projects in the Yellow River basin, North China. Further, this chapter summarizes the studies on related water issues, and discusses the strategies and measures for tackling watershed vulnerability in the basin. Under the influence of both climate change and human activities, temperature and precipitation have vast spatial and temporal variations, resulting in a dramatic change in the hydrology of the river basin. 101.1 INTRODUCTION
The Yellow River is the second largest river in terms of length (5,464 km) and basin area (752,443 km2) in China (see Fig. 101.1). It is also the fifth longest river in the world. It originates in the Qinghai-Tibet Plateau, runs through Qinghai, Gansu, Sichuan, Ningxia, Inner Mongolia, Shanxi, Shaanxi, Henan and Shandong Provinces (or Autonomous Region), and finally debouches into the Bohai Gulf. The Upper Reach of the Yellow River is the part above
95°E
100°E
105°E
Hekou in the Inner Mongolia Autonomous Region; the Middle Reach of the Yellow River is the part between Hekou and Taohuayu in Henan Province; the area downstream of Taohuayu is regarded as the Lower Reach of the Yellow River (see Table 101.1). There are many tributaries, such as the Hei River, Kuye River, Wuding River, Fen River, Wei River, Luo River, and so on. The Yellow River exhibits a variety of geomorphology and has three elevation ranges from the source to the river mouth. The Qinghai-Tibet Plateau has an average elevation of over 4000 m, the mountain region has an elevation range of 1000–2000 m, and the North China Plain has an average elevation below 100 m (Yang et al., 2004). Figure 101.2 shows the distribution of land use in the Yellow River basin, and Table 101.2 gives the descriptions of the abbreviations of different land use types and the area percentage of each in the basin. As a semiarid region, water availability is limited in this river basin, whereas water demand is continuously increasing due to both population growth and economic growth. The population in 2005 over this river basin was about 113 million (Chen et al., 2013). The Hetao Plain in the upper region the Fenwei Basin in the
110°E
115°E
120°E
35°N
40°N
Elevation (m) 5000 4500 4000 3500 3000 2500 2000 1500 1000 500 200 100 50
Dam
Longyangxia
Sanmenxia
Xiaolangdi
Figure 101.1 The Yellow River basin and the locations of the large dams. [Source: The photos of three large dams were adopted from the internet.] 101-1
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101-2 Yellow River Basin
Table 101.1 Basic Information of the Yellow River Basin Length (km)
Area (×104 km2)
Elevation range (m)
Upper reach
3472
38.6
3496
0.1
Middle reach
1206
34.4
890
0.074
Region
Slope (%)
Lower reach
786
2.3
93.6
0.012
Entire basin
5464
75.3
4479.6
0.082
Upper reach
Middle reach
Lower reach
35°N
40°N
Coarse sedimen source region
105°E
100°E WT
EN
EB
DN
DB
MF
CS
110°E OS
WS
SV
GL
115°E PW
CL
UB
MO
SI
BS
Figure 101.2 The distribution of land use in the Yellow River basin (see Table 101.2 for the land use types); three photos obtained from the internet showing the typical topographies of upper, middle, and low reaches.
middle region, and the irrigation area in the lower region are the three main agricultural production bases in China. The energy industry, especially for the coal industry, accounts for nearly half of the national total. According to available statistics, 65% of the total water volume of the Yellow River was utilized from 1986 to 1997 (Xu, 2007). As a result, the water resources in the Yellow River basin make a great contribution to the agricultural and economic development in China. Moreover, the Yellow River is notorious for its high sediment load from the Loess Plateau, which lies in the middle region.
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A substantial number of soil and water conservation measures have been implemented since the late 1950s, and these measures have markedly changed the hydrological conditions and are of critical importance to the integrated watershed management of the Yellow River basin. Similar to CWRC (see Chapter 100), a river basin authority dispatched by the MWR (Ministry of Water Resources of the People’s Republic of China), the Yellow River Conservancy Commission (noted as YRCC hereafter) takes water administrative functions in the Yellow River Basin.
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Climate and hydrology 101-3 Table 101.2 The Abbreviations of Different Land Use Types and Area Percentages in the Yellow River Basin MODIS IGBP
Abbreviation
Percentage (%)
Water
WT
0.29
Evergreen needleleaf forest
EN
0.26
Evergreen broadleaf forest
EB
0.00
Deciduous needleleaf forest
DN
0.01
Deciduous broadleaf forest
DB
0.50
Mixed forest
MF
6.60
Closed shrublands
CS
0.29
Open shrublands
OS
2.16
Woody savannas
WS
0.11
Savannas
SV
0.03
Grasslands
GL
64.32
Permanent wetlands
PW
0.01
Croplands
CL
21.14
Urban and built-up
UB
1.20
Cropland/Natural vegetation mosaic
MO
1.12
Snow and ice
SI
0.01
Barren or sparsely vegetated
BS
1.95
101.2.1 Temperature
The Yellow River basin is located mainly in the temperate climate zone, with large seasonal and interannual variations of temperature, precipitation, and runoff (Chen et al., 2013). According to the regional differences in climate and geomorphology, the river basin is separated into three subregions (i.e., the eastern monsoon region, the arid and semiarid region, and the high-elevation region) (Liang et al., 2014), where the climatic characteristics are significantly different. Moreover, due to the rapid socioeconomic development, the hydrology of this river basin (especially in the middle reaches) has
Precipitation (mm/yr)
30
Upper
25 20
5 0
100
–5
50
–10 J F M A M J
J A S O N D
120°E 140
–15
120 100 80 60 40 20 0 1950 1960 1970 1980 1990 2000 2010
35°N
40°N
115°E
10
150
0
110°E
15
200
700 600 500 400 300 200
The mean annual precipitation in this river basin is mostly between 300 and 700 mm, with highly uneven spatial and temporal distributions (see Fig. 101.3). Precipitation declines across this river basin from east to west, ranging from 368 mm in the upper reaches to 530 mm in the middle reaches and 670 mm in the lower reaches, and more than 60% of the annual precipitation occurs during the rainy season (from June to September) (Yang et al., 2010). A significant decreasing trend in the annual precipitation can be detected in the whole river basin since the 1970s; and a higher risk of drought can be expected in spring and autumn due to the decreasing precipitation in these two seasons (Zhang et al., 2014). For the daily precipitation extremes, Zhang et al. (2014) indicated that they are not dominant in the basin except for some regions in the North China Plain, and rainstorm events are generally decreasing. Using the data recorded at 75 meteorological stations for the period of 1959–2008, Wang et al. (2013) also revealed that changes in precipitation extremes revealed a drying trend, but most of the changes were statistically insignificant.
Annual runoff (mm)
300
1 250
The mean annual temperature of the basin is approximately 8°C (Liang et al., 2014), with significant seasonal variation. Temperature basically declines across this river basin from the southeast area to the northwest region. The mean annual temperature in the lower reach of the Yellow River is around 14°C, while that in the source area of the river is only –4°C (see Fig. 101.3). Moreover, the diurnal temperature range in this river basin is quite large (up to 16°C). A significant increasing trend in the annual temperature has been detected for the period 1961–2011 over the whole river basin (Liang et al., 2014); such warming trends appear in all seasons, particularly in winter (Wang et al., 2013). For the daily temperature extremes, Wang et al. (2013) indicated that overall increasing trends in both maximum and minimum temperature, significant increasing trends in the frequency of warm days and warm nights, and significant decreasing trends in the frequency of cold days and cold nights can be detected in the whole river basin, based on data recorded at 75 meteorological stations from 1959 to 2008. 101.2.2 Precipitation
101.2 CLIMATE AND HYDROLOGY
95°E
been greatly influenced by human activities (Mu et al., 2007; Ran et al., 2008; Shi et al., 2012; Li et al., 2014; Liang et al., 2014). Research on the variability of climate and hydrology in the past few decades has been undertaken. Temperature, precipitation, and runoff are regarded as the main indicators, and the variability of these factors are introduced in detail in the following text.
300
Main stream flow station Weather station 95°E
100°E
250
30
Middle
25 20
200 150
0
200
10
150
0
50 J F M A M J
J A S O N D
250
15 5
100
300
30
Lower
25 20 15 10
100
–5
50
–10
0
120°E
5 0 –5 J F M A M J
J A S O N D
–10
Figure 101.3 The spatial distribution of the mean annual precipitation for the period 1961–2013 in the Yellow River basin; the locations of the weather stations administrated by the China Meteorological Administration; three inserted charts showing the monthly variations of precipitation and temperature in a year at the upper, middle, and lower regions; the remaining chart showing annual runoff at Lijin, a hydrologic station near the river mouth.
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101-4 Yellow River Basin 101.2.3 Runoff
Although the Yellow River is the fourth largest river in terms of the annual runoff (less than the Yangtze River, the Pearl River, and the Songhua River), with the value of 58 billion m3/yr, accounting for 2.1% of the national total, it is surely the most important source for water supply in Northwestern and Northern China. In the basin, water resources decrease from south to north and have a markedly uneven spatial distribution. In addition, the temporal distribution is also uneven, and nearly 60% of the runoff is concentrated in the flood season (from June to September), occurring in response to shortduration and high-intensity rainstorms. Figure 101.3 also shows the variation of annual runoff at the Lijin station in the Yellow River basin from 1950–2012. Most of the river runoff comes from upstream of Lanzhou City in Gansu Province. The runoff decreases from Lanzhou City to the Hekou station due to the evaporation and seepage losses. The runoff yield increases in the region between the Hekou station and Taohuayu station; however, a significant decreasing trend in the annual runoff can be detected in recent years, mainly due to human activities (Xu and Wang, 2011; Shi et al., 2012). The river reach from the Huayuankou station to the river mouth is widely known as a suspended river because the river channel bed of this part is higher than the surrounding land surface. This suspended river raises the vulnerability to floods (Chen et al., 2013). The most severe flood since 1919 occurred in the river reach between the Sanmenxia and Huayuankou stations in 1958. The flood resulted in the interruption of the Beijing-Guangzhou railway, the main transport route in mainland China, for 14 days (Chen et al., 2013). On the other hand, since the western and northern parts of the river are located in arid and semiarid regions, where the annual rainfall is less than 250 mm, basin-wide droughts frequently occur. Furthermore, for the period of 1972–1996, the downstream
< .08
area of the river suffered from the situation of dried-up river courses; specifically in 1997, such a situation lasted 226 days; the annual economic loss was more 1.1 billion RMB Yuan for the period (Chen et al., 2013). In this chapter, the same data and method used in Chapter 100 are adopted to estimate the spatial variation of drought and flood prone areas in the Yellow River basin (see Fig. 101.4). From Fig. 101.4(a), we can observe that part of the upper region is prone to drought hazard. Fig. 101.4(b) shows that part of the upper region and the south of middle region are prone to flood hazard. 101.3 STATION NETWORK AND WATER CONSERVANCY PROJECTS
In order to better understand the change of climate and hydrology, it is necessary to establish a network of meteorological and hydrological stations. Moreover, water conservancy projects are planned and constructed to better manage water resources in the basin. Regarding the observation networks, similar to the information presented in Chapter 100, there are many observation networks established by different agencies in China. Specifically, China Meteorological Administration (CMA) has a basic standard station network. In this Chapter, basic standard stations established by the CMA are used, and 88 meteorological stations are available in the Yellow River basin, which almost uniformly cover the entire river basin (see Fig. 101.3). The daily observation data, including precipitation, air temperature (mean, minimum, and maximum), air pressure (mean, minimum, and maximum), relative humidity (mean and minimum), wind speed (mean and maximum), and sunshine time, are provided by the National Climate Center of the CMA, and they can be obtained from the China Meteorological Data Sharing Service System (http://cdc.cma.gov.cn/).
(a)
.08 – .1 .10 – .12 .12 – .14 .14 – .16 .16 – .18 .18 – .2 .20 – .22 > .22
< –.016 .016 – .02 .020 – .024 .024 – .028 .028 – .032 .032 – .036 .036 – .04 .040 – .044 > .044
(b)
Figure 101.4 The spatially distributed frequencies of (a) droughts and (b) floods for the period 1961–2013 in the Yellow River basin.
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Research on the Yellow River basin 101-5
In addition, among the hydrological streamflow stations available in the Yellow River basin, the Hekou and Taohuayu stations are the control stations of the upper, middle, and lower reaches, respectively. For the tributaries, the Wenjiachuan station in the Kuye River basin, the Baijiachuan station in the Wuding River basin and the Huaxian station in the Wei River basin are all control stations (see Fig. 101.1). The daily discharge data at these stations can be obtained from the Hydrological Year Book published by the Hydrological Bureau of the Ministry of Water Resources of China, the YRCC, and the Data-sharing Network of China Hydrology (http://www.hydrodata.gov.cn). A number of water conservancy projects (e.g., dams and reservoirs) have been constructed in the Yellow River basin in the past several decades. The dam data can be derived from the International Commission on Large Dams (ICOLD, 2013) and Global Reservoir and Dam (GRanD) (Lehner et al., 2011) databases. If the large dams with a reservoir capacity larger than 0.1 km3 and a height higher than 10 m (MWR, 1978) are considered, the number of large dams constructed between 1900 and 2010 is 27, and the spatial distribution of these large dams is shown in Fig. 101.1. Furthermore, the Yellow River is known worldwide for its soil erosion and sediment problems. The area of the coarse sediment source region in the Loess Plateau is about 630,000 km2 (see Fig. 101.2). Serious soil erosion occurs frequently following storms with high-intensity and short-duration, and such storms can contribute over 70% of the annual sediment yield. In the middle reach of the Yellow River, sediment-trapping dams (noted as STDs hereafter), a type of large-sized check dam used to prevent sediment from entering the mainstem, are the most widespread structures (Xu et al., 2004). Generally, a check dam has a maximum drainage area of 10 acres (0.04 km2) and a maximum height of 2 ft (0.61 m). However, design standards for the drainage area and height of the STDs in this region are no less than 1 km2 and 5 m, respectively (UMYRB, 2005), which are much larger than those of the usual check dam. In addition, the STD structure is usually a simple structure and does not contain a spill tunnel or spillway, which leads to the complete interception of water and sediment from upstream areas. Pervasive STDs have had a substantial impact on the hydrological processes in the study area (Xu et al., 2004; Mu et al., 2007). According to the available statistics, most of the STDs in the Yellow River basin were built between the late 1960s and middle 1970s; however, more than 80% were destroyed by extreme flood events that occurred in 1977 and 1978 (Xu et al., 2004). Another upsurge of STD construction occurred in the late 1980s and the 1990s, and 1,118 STDs were constructed from 1986 to 1999 on the Loess Plateau. To mitigate watershed land degradation and restore the green lands over the Yellow River basin, policies, such as the GTGP (Grain to Green Program) and NFCP (Natural Forest Conservation Program), were implemented in 1999. In addition, the largest water diversion project in mainland China, namely the South-to-North Water Diversion Project, is extremely important to the social and economic development of the Yellow River basin, as it is one of the recipient river basins of diverted water. It is expected that with the water from the Yangtze River, the situation of the groundwater over-pumping in the Yellow River basin can be alleviated, which has caused serious problems such as land subsidence. 101.4 SIGNIFICANT WATER ISSUES
In order to develop better strategies for watershed management, an integrated, physically based, and distributed soil erosion model is highly desirable. Examples include WEPP (Water Erosion Prediction Project),
EUROSEM (European Soil Erosion Model), ANSWERS (Areas Non-point Source Watershed Environmental Response Simulation), LISEM (Limburg Soil Erosion Model) and so on. However, each of these widely used erosion models has limitations for representing interacting processes in the Loess Plateau, as there are two aspects contributing to the complexity and uniqueness of soil erosion processes in this highly erodible region. First, sediment concentration can easily reach as high as 1000 kg/m3, and such a high concentration is rare in other river basins over the world; high sediment load in runoff may increase the detachment rate in rills rather than causing a decrease of channel erosion as assumed in most erosion models (Foster and Meyer, 1972). Second, the steep nature of hillslopes exceeds the gentle slope assumed in most erosion models; gravitational erosion (e.g., collapse and landslide), which rarely occurs in other river basins of the world, happens frequently in gullies of the Yellow River, but this process is not considered in most erosion models. To develop a model for the Yellow River, a research team in Tsinghua University in Beijing, China, has developed a new erosion model that can better represent the erosion processes of the Loess Plateau since 2000. Wang et al. (2007; 2015) developed a framework of a physically based, distributedparameter and continuous erosion model platform at the river basin scale, namely the Digital Yellow River Integrated Model (DYRIM). The DYRIM is designed to comprise a water yield model and hydraulic soil erosion model for hillslopes, a gravitational erosion model for gullies, and a non-equilibrium sediment transport model for channels (Li et al., 2009). The DYRIM uses the high-resolution digital drainage network extracted from the Digital Elevation Model (DEM) data to simulate streamflow generation and water movement, and the drainage network is coded by the modified binary tree method (Li et al., 2010). The DYRIM also takes advantage of RS- and GIS-based parameter acquisition. Moreover, dynamic parallel computing technology has been developed to speed up the simulation (Li et al., 2011; Wang et al., 2011). The DYRIM can facilitate the investigation of sediment dynamics and modeling and has been applied in different sub-basins in the middle Yellow River, and this model is capable of simulating the processes of sediment yield and transport in large-scale river basins. Moreover, the above-mentioned soil and water conservation in the Yellow River basin are regarded as the most important impact factor to the integrated watershed management. Overall, the annual runoff and sediment discharge in the middle reaches exhibits a statistically significant decreasing trend over the past several decades that differed from the general trend of interannual variation associated with climate change and the declining trend for runoff and sediment cannot be well explained by climate change alone (Xu, 2007; Shi and Wang, 2015). Therefore, human impacts in this region must be considered, which can be evaluated using the DYRIM. 101.5 RESEARCH ON THE YELLOW RIVER BASIN
The Yellow River has played a critical role in the socioeconomic development of China, and a large amount of research has been conducted in recent years. It is known from the Web of Science that the number of published papers about the Yellow River in the last 10 years generally showed an increasing trend (see Table 101.3). Moreover, the Chinese Government has invested heavily in terms of research projects on Yellow River basin. According to the data obtained from the official website of National Natural Science Foundation of China (NSFC), the number of NSFC projects about the Yellow River has also been increasing, especially in the recent 4 years (see Table 101.3).
Table 101.3 The Number of Published Papers and National Natural Science Foundation of China (NSFC) Projects about the Yellow River in the Period 2004–2013
Year
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
Paper
60
35
47
63
72
131
228
138
199
187
NSFC
13
8
12
17
18
11
23
31
24
30
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101-6 Yellow River Basin 101.6 CONCLUDING REMARKS
Due to a variable and changing climate and human activities, the hydrological processes of the Yellow River basin have been greatly affected. The decreasing trend in the annual runoff, found in the middle reaches and the suspended river in the lower reaches, increases the risk of flood and drought. The change of the annual sediment discharge in the mainstem is another key problem. The strategies and measures for tackling these challenges include building water conservancy projects, strengthening water regulation capability, and improving integrated watershed management. A number of water conservancy projects (e.g., the massive STDs) have been built in the past several decades. After the completion of these and other projects, the integrated management of the Yellow River basin will be significantly improved. Future work should focus on the protection of environment and natural resources when implementing projects, directed by the idea of the harmony of human and nature. REFERENCES
Chen, J., J. Niu, and L. Sun, Water resources of Mainland China, Climate Vulnerability: Understanding and Addressing Threats to Essential Resources, Elsevier, Academic Press, Cambridge, Massachusetts, 2013, pp. 195–211. Foster, G. R. and L. D. Meyer, “Transport of particles by shallow flow,” Transactions of the American Society of Agricultural Engineers, 15 (1): 99–102, 1972. International Commission on Large Dams (ICOLD), The World Register of Dams, ICOLD, Paris, 2013, http://www.icold-cigb.net. Lehner, B., C. R. Liermann, C. Revenga, C. Vorosmarty, B. Fekete, P. Crouzet, P. Doll, et al., Global Reservoir and Dam Database, Version 1 (GRanDv1): Reservoirs, Revision 01, 2011, http://sedac.ciesin.columbia.edu/ data/set/grand-v1-reservoirs-rev01. Li, E. H., X. M. Mu, G. J. Zhao, P. Gao, and H. B. Shao, “Variation of runoff and precipitation in the Hekou-Longmen region of the Yellow River based on elasticity analysis,” The Scientific World Journal, 2014: 1–11, 2014, doi: 10.1155/2014/929858. Li, T. J., G. Q. Wang, Y. F. Huang, and X. D. Fu,. “Modeling the process of hillslope soil erosion in the Loess Plateau,” Journal of Environmental Informatics, 14 (1): 1–10, 2009. Li, T. J., G. Q. Wang, and J. Chen, “A modified binary tree codification of drainage networks to support complex hydrological models,” Computers & Geosciences, 36: 1427–1435, 2010. Li, T. J., G. Q. Wang, J. Chen, and H. Wang, “Dynamic parallelization of hydrological model simulations,” Environmental Modelling & Software, 26: 1736–1746, 2011. Liang, K., P. Bai, J. J. Li, and C. M. Liu, “Variability of temperature extremes in the Yellow River basin during 1961–2011,” Quaternary International, 336, 52–64, 2014. MWR (Ministry of Water Resources of the People’s Republic of China), Classification and design standards of hydraulic and hydropower project (SDJ12-78), MWR, Beijing, 1978 [in Chinese].
101_Singh_ch101_p101.1-101.6.indd 6
Mu, X. M., L. Zhang, T. R. McVicar, B. Chille, and P. Gau, “Analysis of the impact of conservation measures on stream flow regime in catchments of the Loess Plateau, China,” Hydrological Processes, 21: 2124–2134, 2007. Ran, D. C., Q. H. Luo, Z. H. Zhou, G. Q. Wang, and X. H. Zhang, “Sediment retention by check dams in the Hekou-Longmen section of the Yellow River,” International Journal of Sediment Research, 23: 159–166, 2008. Shi, C. X., Y. Y. Zhou, X. L. Fan, and W. W. Shao, “A study on the annual runoff change and its relationship with water and soil conservation practices and climate change in the middle Yellow River basin,” Catena, 100: 31–41, 2012. Shi, H. Y. and G. Q. Wang, “Impacts of climate change and hydraulic structures on runoff and sediment discharge in the middle Yellow River,” Hydrological Processes, 29(14): 3236–3246, 2015, doi:10.1002/hyp.10439. UMYRB (Upper and Middle Yellow River Bureau, YRCC), Overview of Sediment Trapping Dams, China Planning Press, Beijing, 2005 [in Chinese]. Wang, G. Q., B. S. Wu, and T. J. Li, “Digital Yellow River Model,” Journal of Hydro-Environment Research, 1 (1): 1–11, 2007. Wang, G. Q., X. D. Fu, H. Y. Shi, and T. J. Li, “Watershed sediment dynamics and modeling: a watershed modeling system for Yellow River,” Advances in Water Resources Engineering: Handbook of Environmental Engineering, edited by C. T. Yang,. and L. K. Wang. SpringerCham Heidelberg New York Dordrecht London, Vol. 14, 2015, pp. 1–40. Wang, H., X. D. Fu, G. Q. Wang, T. J. Li, and J. Gao, “A common parallel computing framework for modeling hydrological processes of river basins,” Parallel Computing, 37: 302–315, 2011. Wang, W. G., Q. X. Shao, T. Yang, S. Z. Peng, Z. B. Yu, J. Taylor, W. Q. Xing, et al., “Changes in daily temperature and precipitation extremes in the Yellow River basin, China,” Stochastic Environmental Research and Risk Assessment, 27: 401–421, 2013. Xu, J. X., “Impact of human activities on the stream flow of Yellow River,” Advances in Water Science, 18 (5): 648–655, 2007 [in Chinese]. Xu, J. X. and H. B. Wang, “Influence of soil and water conservation measures on reducing in frequency of hyperconcentrated flows in the Wudinghe River basin,” Environmental Earth Sciences, 62: 1513–1520, 2011. Xu, X. Z., H. W. Zhang, and O. Y. Zhang, “Development of check-dam systems in gullies on the Loess Plateau, China,” Environmental Science & Policy, 7: 79–86, 2004. Yang, D. W., C. Li, H. P. Hu, Z. D. Lei, S. X. Yang, T. Kusuda, T. Koike, et al., “Analysis of water resources variability in the Yellow River of China during the last half century using historical data,” Water Resources Research, 40: W06502, 2004. Yang, T. C-Y. Xu, Q. Shao, X. Chen, G. H. Lu, and Z. C. Hao, “Temporal and spatial patterns of low-flow changes in the Yellow River in the last half century,” Stochastic Environmental Research and Risk Assessment, 24 (2): 297–309, 2010. Zhang, Q., J. T. Peng, V. P. Singh, J. F. Li, and Y. Q. D. Chen, “Spatio-temporal variations of precipitation in arid and semiarid regions of China: the Yellow River basin as a case study,” Global and Planetary Change, 114: 38–49, 2014.
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