89
Tecnología y Ciencias del Agua
, vol. VIII, núm. 2, marzo-abril de 2017, pp. 77-91
Mao
et al.
,
The runoff variation characteristics of Dongting Lake in China
ISSN 2007-2422
•
Wet years alternate with dry years regularly
in four rivers’ regions. The normal flow percent-
ages in Xiang River, Zi River, Yuan River and Li
River are 22.95, 40.98, 36.07 and 27.87%, respec-
tively, which accounts for the maximum pos-
sibilities of five classes. Percentages of normal
years are followed by that of wet years and dry
years who always appear in a short time which
shows the water distribution is well allocated in
four
rivers. According to three bayous’ wet and
dry period, Songzikou’s inter annual runoff is
variable while Taipingkou’s is evener. The wet
year percentage and the dry year percentage of
Ouchikou are 32.79 and 57.38%. The dramatic
inter annual change doesn’t make for the ra-
tional development of water resources. Three
bayous’ drought possibility increases, with the
dry percentage of Ouchikou the maximum,
which indicates a higher risk of drying up and
ultimately threatens the water utilization. The
lake’s discharge is related to the atmospheric
circulation, precipitation change, ENSO and
solar activity.
According to M-K test results, four rivers’
runoff within the statistical time were mutated,
the annual runoff trends fluctuate up and down,
but did not break the confidence intervals. Thus
the change is not significant. As can be seen, the
hydraulic engineering constructions, water and
soil conservation and other measures in four
watersheds play significant ecological effects.
Songzikou’s flow mutation occurred in 1985,
after that, runoff showed significant attenua-
tion changes, which may be one of the effects
of the completion of the Gezhou dam in 1981.
Taipingkou’s mutation time happened in 1985
which is consistent with that of Songzikou and
a breakthrough confidential threshold in 1990
showed significant attenuation trend. Ouchikou
broke the confidential threshold in 1989 then
exhibited a significant attenuation trend after-
ward. From 1967 to 1972, after Jingjiang channel
straightening, Ouchikou’s flow was greatly af-
fected and decayed sharply.
The stage changes in runoff are affected by
human activities and nature factors. Climate
change takes the main responsibility for the
runoff stage evolution, meanwhile, water and
soil erosion, hydraulic engineering construc-
tions and human activities accelerate the change
progress. In climate respect, four rivers’ flood
peak encounters with that of three bayous’ is
the main cause of lake’s flood disaster. Since the
1990s, the Yangtze River basin has experienced
several large precipitation progress, a flood
from four rivers and three bayous superim-
posed on each other and lead substantial water
to the lake. At the same time, the water level of
outflow was very high. As a result, abundant
income and flood water jacking yielded a high
water level of the lake and caused severe flood
disasters. Floods in 1954 and 1998 are such
typical examples. Human activities don’t affect
four rivers significantly for their water amount
is large and inter annual fluctuation is small.
But channel straightening, constructions of
Three Gorge and Gezhou dam have changed the
natural law between Dongting Lake and Yang-
tze River. Three bayous’ runoff attenuation has
resulted in the seasonal drought of Dongting
Lake. In conclusion, the appearance of Lake
Flood is the result of floods superimposition by
the flood from three bayous and four rivers. In
the long-term, climatic is the dominant factor
causes runoff change, while human activities
such as building dam intensify the procedure.
The runoff variation of Dongting Lake are
caused by the comprehensive impact of climate
change and human activities, but how many
the contribution rate of the two kind factors to
runoff variation at inflows, outflow and total-
ity respectively, what are the drive mechanism
causing the difference of the contribution rate et
al. These will be researched in future.
Acknowledgments
This study was supported by the Key Research Project
of Hunan Provincial Education Department (grant no.
15A113), the Construct Program of the Key Discipline in
Hunan Province of China (2011001) and the Key Research
Project of Hunan Provincial Water Resources Department
(grant no. [2015]13-22).
