Flood Defense and Water/Sediment Management—With Particular Reference to The Yellow River - River Dynamics and Integrated River Management - page 354

6.3.2.4 Impacts of Water Resources Utilization on the Environment
Water utilization from the Yellow River affects the environment positively and negatively. The positive
effects are: (a) promoting development of industry and agriculture, improving water supply, and enhancing
the living standard of the local people; (b) developing forests and improving the environment in the area.
To the south of the Xiao-Qing River, water diverted from the Yellow River promotes the recharge of local
ground water and stops ground water depression. The seepage of surface and irrigation water desalinizes
ground water and prevents salt water intrusion; (c) water diversion projects and reservoirs increase the
water surface area and evaporation may increase the humidity of the air and change the local climate.
The surface water may be used for recreation; and (d) utilization of highly silt-laden water from the
Yellow River for land fill and ground level increase also improves soil quality and promotes agricultural
development.
The negative effects are: (a) salinization induced by irrigation water percolation, and by seepage from
canals and reservoirs; (b) occupation of land by water diversion works and reservoirs, and displacement
of inhabitants from the by area submerged reservoirs; (c) reduction of water and sediment flowing into
the sea may affect the species living in the waters and wetlands near the Yellow River mouth; and (d)
desertification induced by deposition of sediment from diversion of heavily silt-laden flood water.
Nevertheless, the negative effects on the environment can be reduced to the minimum by applying proper
management strategies.
6.4 New Problems in the Yellow River Management
6.4.1 Power Generation Reduces the Channel Capacity
The 11 reservoirs on the Yellow River: Longyangxia, Lijiaxia, Liujiaxia, Yanguoxia, Bapanxia, Qingtongxia,
Sanshenggong, Wanjiazhai, Tianqiao, Sanmenxia, and Xiaolangdi have a total capacity of 55.8 billion m 3 ,
equal to the annual runoff of the whole watershed. The total installed capacity of power generation is
5,620 MW, of which 1,280 MW is at Longyangxia, 2,000 MW at Lijiaxia, and 1160 MW at Liujiaxia.
These power plants generate 23 billion kw-hr per year, of which the 3 major power stations generate 6
billion kw-hr each. The reservoirs are operated mainly according to the requirements of power generation
and water supply without consideration of the natural features of the river and maintenance of a high
capacity for sediment transportation in the channel. The reservoirs store water the during flood season
and release water in the non-flood season for power generation. Therefore, the flood peaks are flattened
and much less water is transported at high discharges. Flows in the middle and lower Yellow River have
changed remarkably.
The Sanmenxia Reservoir is the most downstream reservoir on the Yellow River about 1,000 km
upstream from the river mouth. The Longmen Hydrological Station is about 230 km upstream from
Sanmenxia Dam and the measured water and sediment at the station reflects the influence of human
activities in the middle and upper watersheds. Figure 6.22 illustrates the runoff volume at different
discharges at the Longmen Hydrological Station in the flood season (July to September). From 1950-1969
more than 7 billion m 3 of water, or 30% of the runoff in flood season, was transported at a discharge of
about 3,000 m 3 /s. In the period 1970-1985, the peak runoff-conveying discharge was still 3, 000 m 3 /s but
only 3.8 billion m of water flowed at that rate. In the period 1986-1995, however, the peak runoff-
conveying discharge reduced to 1,500 m 3 /s, which reflects the effects of discharge-regulation by the
reservoirs, water diversion, and soil and water conservation works in the watershed (Pan and Li, 1998).
The average annual runoff and sediment load released from the Sanmenxia Reservoir to the lower
reaches of the river in the period 1986-1994 were 30.7 billion m 3 and 0.8 billion tons which were 11.3