Journal of Geographical Sciences >
Multiscale variability of water discharge and sediment load into the Bohai Sea from 1950 to 2011
^{*}Corresponding author: Li Guosheng, Professor, Email:ligs@igsnrr.ac.cn
Author: Ren Huiru (1983), PhD Candidate, specialized in coastal environment and modeling. Email:renhr.12b@igsnrr.ac.cn
Received date: 20140420
Accepted date: 20140526
Online published: 20150115
Supported by
National Natural Science Foundation of China, No.41271026
Copyright
This paper examines the changes in the time series of water discharge and sediment load of the Yellow River into the Bohai Sea. To determine the characteristics of abrupt changes and multiscale periods of water discharge and sediment load, data from Lijin station were analyzed, and the resonance periods were then calculated. The MannKendall test, order clustering, powerspectrum, and wavelet analysis were used to observe water discharge and sediment load into the sea over the last 62 years. The most significant abrupt change in water discharge into the sea occurred in 1985, and an abrupt change in sediment load happened in the same year. Significant decreases of 64.6% and 73.8% were observed in water discharge and sediment load, respectively, before 1985. More significant abrupt changes in water discharge and sediment load were observed in 1968 and 1996. The characteristics of water discharge and sediment load into the Bohai Sea show periodic oscillation at interannual and decadal scales. The main periods of water discharge are 9.14 years and 3.05 years, whereas the main periods of sediment load are 10.67 years, 4.27 years, and 2.78 years. The significant resonance periods between water discharge and sediment load are observed at the following temporal scales: 2.86 years, 4.44 years, and 13.33 years. Water discharge and sediment load started to decrease after 1970 and has decreased significantly since 1985 for several reasons. Firstly, the precipitation of the Yellow River drainage area has reduced since 1970. Secondly, largescale human activities, such as the building of reservoirs and floodgates, have increased. Thirdly, water and soil conservation have taken effect since 1985.
REN Huiru , LI Guosheng , CUI Linlin , HE Lei . Multiscale variability of water discharge and sediment load into the Bohai Sea from 1950 to 2011[J]. Journal of Geographical Sciences, 2015 , 25(1) : 85 100 . DOI: 10.1007/s1144201511551
Figure 1 Sketch map of the Bohai Sea (Data are from National Fundamental Geographic Information System in 2003, NGCC.) 
Figure 2 The temporal variation of annual mean for water discharge and sediment load 
Figure 3 MannKendall test for abrupt change of the Yellow River at Lijin station(a. annual water discharge; b. annual sediment load) 
Table 1 Jumping points of water discharge and sediment load of the Yellow River into the Bohai Sea 
Water discharge  Sediment load  

The first jumping points  1985  1985 
The second jumping points  1968, 1985, 1996  1968, 1985, 1996 
The third jumping points  1964, 1968, 1985, 1996, 2002  1959, 1963, 1968, 1985, 1996 
Figure 4 The stepwise decrease of the water discharge and sediment load at Lijin station (a. water discharge; b. sediment load) 
Figure 5 The powerspectrum of water discharge of the Yellow River into the Bohai Sea (a); The powerspectrum of sediment load of the Yellow River into the Bohai Sea (b) 
Figure 6 Morlet wavelet transform of monthaveraged water discharge at Lijin station (a. wavelet coefficients as a function of period and time; b. the wavelet power spectrum with period) 
Figure 7 Time series of water discharge rate from 1950 to 2011 (a. original time series; b. the reconstruction of the Db6 wavelet in intraannual scale; c. the reconstruction of the Db6 wavelet in annual scale; d. the reconstruction of the Db6 wavelet in decadal scale; e. component and tendency signal) 
Figure 8 Morlet wavelet transform of monthaveraged sediment at Lijin station (a. wavelet coefficients as a function of period and time; b. the wavelet power spectrum with period) 
Figure 9 Time series of the sediment rate from 1950 to 2011 (a. original time series; b. the reconstruction of the Db6 wavelet in intraannual scale; c. the reconstruction of the Db6 wavelet in annual scale; d. the reconstruction of the Db6 wavelet in decadal scale; e. component and tendency signal) 
Table 2 Crossspectrum density of water discharge and sediment load at Lijin station 
k  f  T  

0  0.000  0.216  0.000  0.975  0.000  0.000  
1  0.157  40.000  0.265  0.025  0.927  0.093  0.593 
2  0.314  20.000  0.046  0.019  0.621  0.399  1.270 
3  0.471  13.333  0.048  0.022  0.997  0.435  0.924 
4  0.628  10.000  0.034  0.022  0.783  0.579  0.921 
5  0.785  8.000  0.018  0.007  0.501  0.361  0.460 
6  0.942  6.667  0.008  0.000  0.226  0.001  0.001 
7  1.100  5.714  0.007  0.000  0.180  0.003  0.003 
8  1.257  5.000  0.017  0.002  0.605  0.099  0.079 
9  1.414  4.444  0.029  0.005  0.850  0.160  0.113 
10  1.571  4.000  0.020  0.008  0.648  0.395  0.252 
11  1.728  3.636  0.008  0.009  0.425  0.803  0.465 
12  1.885  3.333  0.015  0.006  0.621  0.380  0.202 
13  2.042  3.077  0.030  0.002  0.925  0.079  0.039 
14  2.199  2.857  0.037  0.001  0.959  0.021  0.009 
15  2.356  2.667  0.024  0.002  0.954  0.063  0.027 
16  2.513  2.500  0.013  0.001  0.944  0.053  0.021 
17  2.670  2.353  0.009  0.001  0.874  0.147  0.055 
18  2.827  2.222  0.008  0.002  0.772  0.203  0.072 
19  2.985  2.105  0.010  0.003  0.899  0.246  0.083 
20  3.142  2.000  0.005  0.000  0.949  0.000  0.000 
Figure 10 Annual precipitation of the Yellow River and water discharge at Lijin station from 1950 to 2011(water discharge at Lijin station in real line; annual precipitation of the Yellow River in dashed) 
Figure 11 The jumping phases of the stepwise decline and periods of water discharge and sediment load(a. water discharge; b. sediment load) 
The authors have declared that no competing interests exist.
1 

2 

3 

4 

5 

6 

7 

8 

9 

10 

11 

12 

13 

14 

15 

16 

17 

18 

19 

20 

21 

22 

23 

24 

25 

26 

27 

28 

29 

30 

31 

32 

33 

34 

35 

36 

37 

38 

39 

40 

41 

42 

43 

44 

45 

46 

47 

48 

49 

50 

51 

52 

/
〈  〉 