Dams and Impounded Rivers - River Dynamics and Integrated River Management - page 409

T able 7.9 Reservoir sedimentation in China (after IRTCES, 1985)
Reservoir River Drainage

area (km 2 )

Dam height
(m)

Total capacity
(10 6 m 3 )

Years
surveyed

Sedimentation
(10 6 m 3 )

Capacity
loss (%)

Liujiaxia Yellow 181,700 147 5,720 1968-78 580 10.1

Yanguoxia Yellow 182,800 57 220 1961-78 160 72.7

Bapanxia Yellow 204,700 43 49 1975-77 18 36.7

Qintongxia Yellow 285,000 42.7 620 1966-77 485 78.2

Sansengong Yellow 314,000 10 80 1961-77 40 50

Tianqiao Yellow 388,000 42 68 1976-78 7.5 11

Sanmenxia Yellow 688,421 106 9,640 1960-78 3,760 39

Bajiazui Puhe 3,522 74 525 1960-78 194 37

Fengjiashan Qianhe 3,232 73 389 1974-78 23 5.9

Heisonglin Yeyu 370 45.5 8.6 1961-77 3.4 39

Fenhe Fenhe 5,268 60 700 1959-77 260 37.1

Guanting Yongding 47,600 45 1,270 1953-77 552 43.5

Hongshan Xiliao 24,486 31 1,560 1960-77 475 30.4

Naodehai Laoha 4,501 41.5 196 1942 38 19.5

Yeyuqn Mihe 786 23.7 168 1959-72 12 7.2

Gangnan Hutuo 15,900 63 1,558 1960-76 235 15.1

Gongzui Dadu 76,400 88 351 1967-78 133 38

Bikou Bailong 27,600 101 521 1976-78 28 5.4

Danjiangkou Hanjiang 95,217 110 16,050 1968-79 897 5.6

Xinqiao Hongliu 1,327 47 200 14 years 156 78

T able 7.10 Environmental impacts of reservoir sedimentation (after IRTCES, 1985)
Location

Impact Description and illustration

1) Depletion of effective storage due to reservoir sedimentation.
2) Deposits plug up the mouth of tributaries, making part of the tributary
capacity ineffective. For instance sedimentation in the Guanting Reservoir
forms a bar of 5 m high at the mouth of Guishi River.

1. Loss of storage
capacity

2. Contamination of
the environment

Chemicals absorbed on the surface of sediment particles enter the reservoir
with the sediment. Water quality may deteriorate through ion exchange.

Reservoir

1) Abrasion of turbines due to passage of sediment particles.
2) Abrasion of gate and tunnel by high velocity current with heavy
sediment concentration.
3) Sedimentation raises the reservoir bed to an elevation higher than the
inlet of the power tunnel.

3. Endanger the sluice
structures and abrade
the turbines

1) Sediment deposition in the spawning and breeding zone.
2) Siltation along lake perimeter and growth of aquatic weeds make the
food rich lake bottom inaccessible to birds.

4. Ecological effect

5. Adverse effect on
tourism

Advance of delta renders a part of the lake too shallow for boating and
anchorage.

After draw down of the pool level, sand dunes with considerable height
may form in the reach of fluctuating backwater region, bringing serious
trouble to navigation (Lu, 1981).

Upstream

6. Adverse effect on
navigation

The retrogressive deposition raises the flood stage, enlarges the zone of
inundation, and enhances the flood risk in the reach upstream of the
reservoir. Area of swamp and alkalization enlarged due to rise of the
ground water table.

7. Extension of
reservoir sedimentation
upstream