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TRANSCRIPT
Research on Ecological Effects of Artificial Water Supplement in
Ancient Deltaic Channel of Yellow River Delta, China
Liu Jian*, Guo Lei, Bo Qingwei, Lin Lin,Xin Hongjie
Key Laboratory of Water Resources and Environment, Water Research Institute of
Shandong Province, Jinan, Shandong, China
E-mail: *[email protected]
Abstract
Because of small water discharge and huge sediment load, the Yellow River
changed its channel into the sea for many times and formed several deltaic
channels in the past time. Diaokouhe River is one of the ancient channels before
1976, and it is treated as the backup option for the current Qingshuigou channel of
Yellow River. Because of long term no-discharge, the channel shape and regional
ecosystem degenerate seriously. For saving and protecting the ecology and
environment of Diaokouhe Channel, the management department of Yellow River
Basin carried out artificial water supplement for the channel in 2010 and 2011.
During the period of water supplement, some important index and data, such as
groundwater table, soil salinity, vegetational type, bird population, and so on, was
observed and count systematically. The analysis results indicate that the artificial
water supplement bring positive effects. The effects are:(1) preventing the
saltwater intrusion trend in the degenerative estuarine wetland, (2) controlling the
rapid development of soil salinization, (3) optimizing the ecological types and
landscape structure and controlling retrogressive succession trend of regional
vegetation preliminarily, (4) improving and repairing the wetland biotope and bird
habitat obviously. But some problems also exist there, such as difficult for
transferring large amount of water, huge channel sediment accumulation, and so
on.
Keywords
Ancient deltaic channel, water supplement, ecological effect, Yellow River Delta
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1. Introduction
It is becoming acknowledged that water is likely to be the most pressing environmental
concern of the 21st century [1]. The Yellow River, called as Mother Water of China, is
the second-longest river in China with a length of 5464 km, and also is noted for its
small water discharge and huge sediment load in the world [2] - [4]. Because of
uncoordinated relationship between water and sediment, the river channel continues to
be silted, especially in the downstream. Once sedimentation has progressed to a certain
level, the estuary is prone to change [5] [6].
According to historical records, the Yellow River changed its channel into the sea for
more than 26 times and formed several flow paths in the past 2600 years [7] [8]. In
January 1964, the Yellow River flowed into the Bohai Sea through Diaokouhe deltaic
channel instead of Shenxiangou deltaic channel, and the ninth channel in the Yellow
River Delta was formed. The Diaokouhe channel with whole length of 55km locates at
north of present Yellow River northern levee. In May 1976, the Diaokouhe channel was
replaced by Qingshuigou channel [9] [10]. From 1964 to now, the Diaokouhe channel
flowed for more than 12 years and stopped running water for more than 30 years. The
locations of rivers and deltaic channels in the Yellow River Delta are shown in
Figure.1.
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Figure 1. Locations of rivers and deltaic channels in the Yellow River Delta
During the period of no-discharge, great changes, such as channel cross-section
shape, ecological environment and so on, have taken place because of the influences of
water silt condition, marine dynamics interactions and human activities in Diaokouhe
channel [11].
(1) Without the supplement of sediment, coastline by the Diaokouhe channel began to
erode, and the maximum erosion length is more than 10km.
(2) Because of the lack of fresh water, the surrounding wetland was shrinking and its
biodiversity developed by water-sediment resources was destroyed.
(3) The channel was atrophying seriously and the discharge capacity was reduced
greatly.
(4) Affected by the impacts of human activities, wind and rain erosion and
management lack, the embankment engineering has been incomplete along the
Diaokouhe channel [12].
According to the Comprehensive Control Planning of Yellow River Estuary,
Diaokouhe channel is important for being treated as a backup option for the current
Qingshuigou channel [13]. For improving the regional ecological environment of
Diaokouhe channel and effectively protecting the alternate channel of Yellow River,
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artificial water supplement experiments were implemented in 2010 and 2011
respectively. The observed results indicate that the water supplement achieved good
effects, but some problems also exists. Based on these two artificial experiments, the
effects of water supplement to Yellow River ancient deltaic channel and ecological
environment were analyzed selectively in this paper.
2. Course of Artificial Water Supplement
The artificial water supplement experiments were carried out in the period of Yellow
River water and sediment regulation from June to August, and the water was supplied
by gravity and pumping ship.
In 2010, the total supplied water was 3.62 106 m3. The supplied water stored in
channel, flowed to nature reserve area and discharged into the Bohai sea was 25.42 106
m3, 8.05 106 m3 and 2.73 106 m3, which accounted for about 70.2%, 22.2% and 7.6%
of total supplied water respectively.
In 2011, the total supplied water was 3.618 106 m3, which were similar to those of
2010. The supplied water stored in channel, flowed to nature reserve area and
discharged into the sea accounted for about 83.4%, 12.3% and 4.3% of total supplied
water respectively.
In these two water supplements, water coverage areas were about 2.333 103 hectare
in channel and 1.333 103 hectare in nature reserve.
3. Analysis of Eco-environmental Effects
During the course of two water supplements, the regional eco-environmental situations
were monitored dynamically. The results show that supplied water plays positive roles
for repairing and improving local ecosystem and ecological environment. The positive
influences were shown as followed.
(1) The saltwater intrusion trend in the degenerative estuarine wetland was prevented
preliminarily. The observed results indicated that the groundwater table rose in the
distance range of 1.1km along the channel, and rose significantly in the range of 0.6km.
The maximum uplift amplitude was about 0.65m. In nature reserve, the influence scope
of water supplement to groundwater was about 1.5km. The groundwater table rose
significantly in the distance of 0.5km to nature reserve area, and the maximum uplift
amplitude was 0.45m.
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(2) The rapid development of soil salinization was controlled. The soil salinity
decreased obviously along the Dikouhe River. The salinity in 0-0.3m soil layer
decreased significantly, and average changed percentage was about 48%. Among
which, the average decreased percentages are 55% in 0.1m, and 41% in 0.3m. This laid
the foundation for the growth and development of aquatic and wet vegetation in
freshwater wetland.
(3) The ecological types and landscape structure were optimized in water supplement
area, and retrogressive succession trend of regional vegetation was controlled
preliminarily. The saliferous bare land in low-lying area was covered by water. The low
annual and perennial saline vegetation evolved into reed marsh ecosystem type, and the
tamarix community and hygropium in high terrain also has the trend of evolving into
reed community. During the course of water-supplement and with the soil desalting
process, reed become predominant community adapting to the ecological environment
and the main vegetation habitat of aquatic birds has been formed preliminarily.
(4) The wetland biotope was improved by the change of bird habitat vegetation, and
the habitat of large wader bird was repaired obviously. Aquatic bird populations
increased significantly. In 2010 and 2011, the number of waterfowl increased by 11180
and 36798 respectively. The effect of rare and endangered bird protection is significant
particularly. The number of red-crowned cranesea which is national key protected bird
increased by 11 and 19. The number of Oriental white stork increases by 18 and 149,
and that of black stork added 14 and 4. In 2011, crane was found with the population 14
for the first time, and oriental white stork migrated with a large group of population
152.
4. Problems during the Water-supplement
The ecological water supplement proceeded smoothly in 2010 and 2011. According to
the measured data during the process, some problems also exist there.
(1) The water transfer needs going through Luojiawuzi diversion brake of Yellow
River. Because of high floor elevation, gravity flow can not be achieved when the
Yellow River is in a low water level. The time and quantity of water supplement was
under restriction. If water was supplied by pumping station, the operating cost will
increase. At the same time, obstacles in the channel were not cleared entirely. It can
only cope with experimental water supplement, but can not satisfy the need of long term
and huge amounts of transfer water.
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(2) Because of the prevention of reed and weed, all the sediment deposited in the
channel. The total amount of sediment transferred in the water supplement was more
than 5 105 tons in 2010 and 2011, and the vast majority of it deposited 20km upstream
of the channel. The sediment deposition will bring adverse effect for the water
supplement in the future.
(3) Influenced by the high elevation of natural reserve, more fresh water can not flow
into the core area when supplied water is small. With the limitation of Yellow River
flow and diversion conditions, large capacity of water transfer is unfeasible. So, there
are difficult for transferring water to core area of natural reserve.
5. Conclusion and Discussion
According to the research results, water supplement to ancient estuary channel using
Yellow River have promotive effects on protecting and fixing regional ecological
environment. They basically behave in: (1) preventing the saltwater intrusion trend in
the degenerative estuarine wetland, (2) controlling the rapid development of soil
salinization, (3) optimizing the ecological types and landscape structure and controlling
retrogressive succession trend of regional vegetation preliminarily, (4) improving and
repairing the wetland biotope and bird habitat obviously. But it also exposes some
problems, which include restriction of transfer time and quantity for gravity flow,
sediment accumulation in the river channel, and difficulty of flowing into core area of
natural reserve with small water flow.
As the succession and development of ecosystem, it will be a long-term process for
restoration of degraded wetland. The ecological effects of artificial water transfer in
ancient estuary channel of Yellow River Delta will appear because of long-term
implementation of water transfer and delay of ecosystem succession. So, the
government should establish long-term working mechanism for artificial water
supplement, and carry out scientific investigation, monitoring and research for transfer
process and effect. All the work will be very important for understanding changes of
Diaokouhe deltaic channel, optimizing water allocation and maintaining virtuous cycle
of ecosystem in ancient deltaic channel.
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