3 Case
Study
3.1 Study Areas
The research object of this study is three basins, i.e. Xiangxi River,
Jinghe River and Zhongzhou River. They are tributaries of three
state-level basins in central, northwestern and southeastern China, i.e.
Yangtze River, Yellow River and Pearl River, respectively.
Xiangxi River (110°25′~116°06′E,
30°57′~31°34′N, Fig. 3a), also known as Zhaojun River,
is located in the western part of Hubei Province, China. It is a first
tributary of Yangtze River. Its waterway is 97.3 kilometers and
catchment area is about 3,100 square kilometers. It originated from
Shennongjia and has two sources. The east source is in the Shenmadian,
Shennongjia, and the river turns from east to west and then to
southeast. Since the west is from the south of the Great Shennongjia
Mountain, the river is from the northwest to the southeast. And the
Xiangxi River Basin is located in subtropical monsoon climate with four
distinct seasons.
Jinghe River (106°14′~108°42′E,
34°46′~37°19′N, Fig. 3b) is a secondary tributary in
Yellow River and one of the first tributary in Weihe River. It is
located in the middle of the Loess Plateau. Its waterway is 455.1
kilometers and catchment is 45,421 square kilometers. The river flows
from northwest to southeast. The flood and dry in Jinghe River Basin
vary greatly, and the flood peak period is from July to August.
According to the hydrological data from 1960 to 1987, the average
monthly runoff is more than 160 times the difference between flood and
dry. In addition, due to its location in the Loess Plateau, the soil
erosion is serious. The sediment concentration of Jinghe River is the
highest in the three basins.
Zhongzhou River (107°55′~108°22′E,
24°42′~25°34′N, Fig. 3c), also known as Xiaohuan River,
is located in Huanjiang Autonomous County in Guangxi province, China. It
is a tributary of Pearl River. With a total length of 136.5 kilometers
and drainage area of 2,328 square kilometers, Zhongzhou River is the
second largest river in Huanjiang County. It starts from the Zaibian
District in Congjiang County, Guizhou Province, and flows into Longjiang
River from north to south. The flood peak in Zhongzhou River usually
appeares in June and July, and the runoff was greatly affected by
precipitation.
3.2 Hydro-Climatic Features
According to historical observation data, the climatic and hydrologic
characteristics of the three basins are analyzed. It can be seen from
the monthly average results (Fig. 4) that annual distribution of
precipitation in Xiangxi River and Jinghe River is relatively uniform,
and the two basins have basically the same tendency. The peak
precipitation in Zhongzhou river is obvious, from April to June. The
annual temperature distribution in three basins are similar, and the
overall temperature decreases with the increase of latitude where the
basin in. In terms of runoff, no significant difference between Xiangxi
River Basin and Zhongzhou River Basin, with an average annual runoff of
about 30 m3/s. However, the scale of Jinghe River
Basin is small, and the average annual runoff is only
1.9m3/s. The flood periods of the three basins are
very close, July and August in Xiangxi and Jinghe River, June in
Zhongzhou river.
The interannual variations of climate factors in the three basins are
all not obvious. Interannual coefficient variation (CV) values of
temperature are less than 0.1, and that of precipitation are less than
0.3. However, the variation of runoff has different performance. The
interannual CV of Xiangxi River is 0.30, Jinghe River is 0.62, and
Zhongzhou river is 0.42. One important reason for the large value of
runoff in Jinghe River is the runoff is not plenty in itself. It is
worth mentioning that the correlation coefficient between precipitation
and runoff in Zhongzhou River basin reaches 0.69. In the monthly data,
the correlation coefficient can reach 0.85 which is the highest in the
three basins.
3.3 Data
Hydrological models need to be calibrated and verified firstly.
Observation data is used as the training sample. The above 2/3 of the
training sample is used as the calibrated sample, and the remaining 1/3
is used for verification. Observed precipitation, temperature and runoff
from 1991/1/1 to 2002/12/31, 1960/1/1 to 1978/3/31 and 2009/1/1 to
2012/4/30 are used for model calibration in three basins, i.e. Xiangxi
River, Jinghe River and Zhongzhou River, respectively. And the same data
during 2002/1/1-2008/12/31, 1978/4/1-1987/12/31 and 2012/5/1-2013/12/31
are used for verifying, respectively.