Wang Ling, Liu Jifeng
(Yellow River Conservancy Commission (YRCC), Zhengzhou, P. R. China, 450003)

Abstract:Yellow River Basin is in the middle north China. It has some very different features from other rivers, with complicated physical environmental and special river regime. “Less water with more sediment, different original area of sediment and water, unbalanced sediment discharge relationship” is the remarkable characters of Yellow River water resources, which is the reason why Yellow River water resources system is sensitive and fragile to climate change. Climate change impact on water resources are becoming hotspot in water science research field. Basing on observed data and previous researches, effects of climate change on water resources, extreme hydrological events and water ecosystem in Yellow River basin are discussed in this paper.

Both precipitation and nature runoff in Yellow River tend to decrease in recent fifty years, and decreasing speed of runoff is more than twice that of precipitation. Frequency and intensity of rainstorm and flood are becoming smaller and smaller (Fig. 1). Ice flood in Yellow River is very serious than any other rivers because of its variance reach channel and span of 10 latitude degree. Reach ice regime in Ningmeng reach and lower reach are more serious and easy to take place ice flood disaster. Since 90’s of 20 century, ice regime in Ningmeng reach shows new character with the temperature remarkably rising in winter. Temperature increase caused glacial recession, permafrost melting which conduce to runoff reduction by strengthening the land surface evaporation and soil infiltration. In recent 35 years (1966~2000), glacial area in Animaqing mountain reduced 17% (table 1) and alpine snowline increased about 30m, many lakes disappeared and grass land degenerated, consequently these lead to ecological environment deterioration (Fig. 2). Decreasing of nature runoff leads to a sharp reduction of water fluxes to the ocea, consequently channel shrinkage and secondary suspended river expending, which not only increase the possibility of dike breach but also the wet land shrinking, water quality deterioration and biodiversity destruction in lower reach.

Fig. 1 the maximum flood peak discharge of Huayuankou station

 

Table 1 glacier area change in Yellow River basin

 

Times	Ice Area (km2)	Changed area (km2)	Change rate (%)
Last glacier maximum	391.6
Little ice age maximum	147.8	-243.8	-62
1966	125.5	-17.5	-15.1
2000	103.8	-22.74	-17.3

 

 

 

Fig. 2 Swamps and lakes change upper Duoshixia of source Yellow River

 

 

It shows that climate change has impacted each part of basin water resources system, especially in recent 20~30 years. There are some important issues need to be further studied: 1) Research on the nonlinear relation between climatic factors and extreme events. At present, researches relative to climate change and water resources are only focused on the impact of climate change on average events of hydrology and lack of study of climate change effects on extreme hydrological events. 2) Climate change impacts on river basin integrated management should be pay more attention, such as the impacts of climate change on water and sediment adjustment system, water uniform dispatching, water ecosystem over Loess Plateau and estuary region. 3) Research on adaptive countermeasures to climate change in Yellow River basin should be strengthened. 4) Climate change impacts on water resources in Yellow River should be absorbed advanced methods and approaches used in other important river basins in the world.

Fortunately, studies of climate change impacts on Yellow River are just spring up. Yellow River Conservancy Commission now pays more attention to on climate change impact researches. In order to service to Yellow River Master Plan and “Keep Yellow River healthy life”, researches on impact of climate change in Yellow River basin should give scientific identifying of impacts of climate change and human activities on water resources system and evaluating of water resources trend under climate change scenarios in the future, consequently working out the countermeasures of river basin management to climate change.

 

Keywords: Climate change, Yellow River Basin, Water resources, River basin management