Nu River Seismic Risks

8/2/2019 Nu River Seismic Risks

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Geological impact andpotential danger of

China's Nu River

Hydropower Development

Fan XiaoGeological Research Team, Sichuan Geologyand Mineral Resources Bureau, ChinaTranslation by Guo Xin


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1 -2 3 4 5 6 Catalogue

1. Overview of Nu-Salween River, China Part

2. Geological profile of Nu River

3. Faulted zone and earthquake of Nu River

4. The threat of collapse, landslides and other

geological disasters

5. The issue relating to sediment of reservoir

6. Our point of view and summary


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1 -Overview of Nu-Salween River, China Part


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-

3673

2013

Nujiang - Salween

River rises inQinghai-Tibet Plateau,

South of Tanggula

Mountain, with a total

length of 3673 km,

2013 km of which in

China. It flows

through the Tibet

Region and Yunnan

Province.


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-32.5

38.4%

-5516

90.5%2525

524.1153

21%Nujiang - Salween River covers a total area

of 325,000 square kilometers, 38.4% of the

total drainage area of the China territory;

The drop height of Nujiang - Salween is 5516

meters in China, accounting for 90.5% of the

total.

Salween River has an average annual runoff of

252.5 billion cubic meters, and has an annualrunoff of about 52.41 billion cubic meters in

Yunnan Baoshandaojie Dam (153 kilometers

from Chinese border) . The average runoff at

Chinese border is 21% of its total cubic meters

when it flows into the sea.


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Jiayuqiao

Lushuiqiao


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2

Geological profile of Nu River


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The Nu River is at the

geological crossroad of the

northeastern Indian plate and

Eurasian plate, forms a dense

fault zone due to the strong

compression of the two plates.

Nu River, Lancang and Jinsha

river along the fault zone

created a deep canyon, formed

the natural wonders of the

"Three Parallel Rivers".


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300

2The movement of the Nujiang region is very active and seismic activities are frequent. The ancient

riverbed which is 300 meters higher than the modern ones can be observed on both sides of the Nu.

It can be calculated according to the age of the sediments of the terraces, that the average uplift rate

of the crust of Nu in Yunnan can be more than 2 mm per year.


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400050002000

3000

The elevation of mountains on both sides of Nu are above 4000-5000 m, the depth of the Nu River valley

up to 2000-3000 m. Since the terrain is very steep, landslides, mud-rock flow and other geological

disasters caused by gravity are common. It is one of the famous geological disaster-prone areas in China.


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3 Faulted zone and earthquake of Nu River


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---

-

6In the Hengduan Mountains, the Nujiang River valley is

close to a straight line, between Shula Ridge -

Gaoligongshan and Tanianta Aung San - Nushan - Bi

Luo Snow Mountain, Nujiang Valley is formed along the

Nujiang large fracture. The area is still in intense activity

today, it forms the most important earthquake zone, the

south-west Yunnan earthquake zone.

The Nu large fracture transforms into a series ofnortheast trending fracture after going through Baoshan

and Longling, the seismic activities turns stronger, the

area includes Daying (Dayingjiang), Nan-wan River

(Longchuan) fault, Wanding River (Ruili) - Mans River

(Luxi) fracture, Nujiang (Longling Mu city) fracture,

Nanting River (Mengding) fracture, 6 magnitude

earthquake are commonly seen in the area.


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Nu River fault near Liuku


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145819765186

1632.36

1512197646461530.961976-7.4

20115.8

In the area between eastern Nu and Yuan Jiang upstream, according to the statistics from 1458 to

1976, 16 earthquakes of more than magnitude 6 occurred, once every 32.3 years.

From 1512 to1976, west of Nujiang, there were 15 earthquakes of magnitude more than 6, once

every 30.9 years. Famous earthquake includes the Longling - Lianghe 7.4 magnitude earthquake in

1976. In 2011, a 5.8 magnitude earthquake occurred in Yingjiang.


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On one hand, the seismic activity triggered geological disasters will put the large reservoirs in great

security risk and generate potential risk of secondary chain of disasters; on the other hand, the

construction of the large reservoirs are very more likely to cause earthquakes, resulting in a more

serious disaster.


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It is noteworthy that the Nujiang fault zone,

both the Hengduan Mountains segment andBaoshan and Longling zone, have the

characteristics of sliding along the clockwise

direction parallel to the valley, which will

have serious impact to the dam constructed

perpendicular to the valley.

In the report of Planning of HydroelectricProject in Middle, Downstream Nu River,

prepared by China National Electricity

Research Institute and Huadong Research

Institute, the statistics observed on Nujiang

fault zone activities was not mentioned and

the potential impact on its cascade dam, risk

in bringing earthquake when the reservoir isstored was not assessed.


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4 The threat of collapse, landslides and other geologicaldisasters


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Nu River valley,

especially the Hengduan

Mountains part, is filled

with steep slopes and

deep valleys, fracture and

broken rocks, seismic

activity is frequent and

the rainy season is

concentrated, therefore

the surface movement isvery strong, collapse,

landslide, mudslides and

other geological disasters,

makes river blockage

quite frequently in history.

slide

landslip

mud-rock flow


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7

85

30

Take the river part from Bingzhongluo to

Liuku for example (the part is planning

seven dams), on both sides of Nu River

valley, the tributary channel are all

mudslides channels. The fan-shape

debris are common, making the river

even narrower and forms dangerous

shoals in the main river.

At least 30 mudslides have been

observed around the 85 km section of the

river between Gongshan County andFugong County, Lumadeng. The mud

flows into the Nu River valley and

caused a half-blockage.


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In Gongshan, three large rock fall and cliffs are observed in Danzhu, Yuege and Lietoudi. The

rock fall of Yuege blocked Nu once, and it is still the most dangerous shoal in Nu, named The

Hugest Wave in Nu and the wave can be as high as 7-8 meters.


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7916

Because of the extremely unstable geological condition in Nu, the large-scale excavation in

hydropower projects(the planning for excavation has reached 79,16 million cubic meters) ,

filling, transportation and other activities will inevitably aggravate geological hazards and soil

erosion.


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For example, the Nu highway excavation and pavement widening caused changes in the relatively

stable natural slope angle, increasing the height of the slope, therefore bringing a lot of disaster. The

Bingzhongluo to Chawa Long roads has been unstable with cause of sandstone, slate and other softrocks, and the free surface side had declined by gravity, bended and broken to form cliffs and

dangerous areas.


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201081892

On August 18, 2010, a huge mudslides occurred at Puladi at Gongshan County, Yunnan Province,

resulting in the death of 92 people. The reason comes from the iron mining at upstream of Nus

tributary, Dongyuege. The landslide caused by mining blocked Dongyuege and formed a dammed

lake, the rised water led to dam failure, the flood carried a lot of silt stone and finally formed a

large mudslides. The fact clearly illustrates the possible dangers of large-scale human engineeringactivities in such special geological environment of Nu River.


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On the other hand, in such A high-risk area like Nu, since many disasters

can not be fully forecasted, the investment of the project can be huge,

and may even make some project unfinished or destroy the completed

projects.

In the current planning of Nu Hydropower projects, a complete assessment of

geological environmental impact, geological disaster engineering impact and risk

costs is not included, leaving the vulnerabilities in the whole analyze of invest,ent.


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5 The issue relating to sediment of reservoir


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Sediment in the river can be divided into two parts: First, suspended sediment, ie,

relatively small particles of clay and sand, they can be transported in river in

suspension; Secondly, the bedload, which are pebbles or boulders, they can only

scroll all the way on the river bed to the downstream.


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Due to the special geological and geomorphological environment of the Nu River,

the collapse, landslide, mudslide which comes from upstream brought large

amount of sediment to the riverbed.


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100100

Without the dam, the the river sediment willgradually moved downstream riverbed in

balance. Once the cascade dam is built, only

a part of suspended sediment can be

discharged into the downstream. A lot of

sediment, especially coarse gravel will

continue to accumulate, thereby seriously

affecting the life and efficiency of the dam.

1000.2757.7

People use the proportion of the reservoir capacity and the annual sediment load as indicators to measure

the feasibility and benefits of hydropower projects. Proportion 100 is a critical value, and when it is less

than 100, it will normally cause serious problem.

Currently in the 13 cascade dam of Nu river, 11 has a proportion less than 100, between 0.27 to 57.7.

Theoretically these reservoirs may within several decades or even a shorter time be overwhelmed. If the

amount of transported bedload is added, the problem can be unacceptable. This will significantly degrade

the efficiency of hydropower projects in Nu Area.


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6 Our point of view and summary


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Nujiang hydropower development in the relevantgeological environment is filled with high risks, it will

bring a great deal of security threat of geological

disasters.In addition to the geological risks, the Nujiang

hydropower development will also produce negative

impact on the following issues:


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A series of cascade reservoir will drown the most prosperous, cultivated land of Nu, where

the population is dense, bringing a huge loss to economy. A large number of immigrants

will be moved to the steep terrain, bringing farming and livelihood difficulties, and also

bring great environment pressure;


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Involuntary migration of a large number of indigenous people will cause the disintegration of the

original cultural and social structure, it will undermine the diversity of national cultural heritage ofthe Nu Area.


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The natural rivers of Nu, if changed into a cascade of artificial reservoirs, will greatly impact the

river environment and habitat, reduce aquatic life species. The aquatic ecosystems will be facing

devastation;

Epalzeorhynchus bicornis

Schizothorax nukiangensis Tsao

Gnujiangensis Chen and Yangspnov

Placocheilus cryptonemus


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It will destroy the authenticity of the

natural landscape and environment of

the World Natural Heritage the Three

Parallel Rivers;


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In the existing system, if the

damage to the environment and

indigenous people, the migration,

impoverishment is aimed to

bring huge economic interests to

government and developers, an

inequitable gap will be formed,causing instability and affecting

social harmony


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Therefore, we oppose large-

scale hydropower

development in the Nu River.

We sincerely hope the

stakeholders concerned can

be cautious on the Nu River

Hydropower Development,

and hope to retain a natural,ecological, vigorous Nu-

Salween River not only for

the residents but also for our

planet.


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Nu River Seismic Risks

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