Stepwise decreases of the Huanghe (Yellow River) sediment load (1950?005): Impacts of climate change and human activities

Houjie Wang a,b,⁎, Zuosheng Yang a,b, Yoshiki Saito c, J. Paul Liu d,
Xiaoxia Sun a,b, Yan Wang a,b
a College of Marine Geosciences, Ocean University of China, Qingdao 266100, China
b Key Laboratory of Seafloor Science and Exploration Technology (KLSSET), Ocean University of China, Qingdao 266003, China
c Geological Survey of Japan, AIST, Tsukuba 305-8567, Japan
d Department of Marine Earth and Atmospheric Sciences, North Carolina State University, Raleigh, NC 27695, USA

Abstract
The sediment load delivered from the Huanghe (Yellow River) to the sea has decreased sharply to 0.15?09 metric tons per year
(0.15 Gt/yr) between 2000 and 2005, and now represents only 14% of the widely cited estimate of 1.08 Gt/yr. The river seems to be
reverting to the pristine levels characteristic of the middle Holocene, prior to human intervention. Datasets from 1950 to 2005 from four
key gauging stations in the main stream reveal distinct stepwise decreases in sediment load, which are attributed to both natural and
anthropogenic impacts over the past 56 yr. Completions of two reservoirs, Liujiaxia (1968) and Longyangxia (1985), in the upper reaches
of the river and their joint operations have resulted in stepwise decreases in sediment load coming from the upper reaches. Effective soil
conservation practices in the middle reaches since the late 1970s, combined with the operation of the Sanmenxia and Xiaolangdi
reservoirs, have also caused stepwise decreases in sediment load at Huayuankou in the middle reaches, but the decrease differs from that
observed in the upper reaches.Decrease in precipitation is responsible for 30%of the decrease in sediment load at Huayuankou, while the
remaining 70% is ascribed to human activities in the river basin, of which soil conservation practices contribute 40% to the total decrease.
Sediment retention within reservoirs accounts for 20% of the total sediment load decrease, although there was notable sediment retention
within the Xiaolangdi reservoir from 2000 to 2005. The remaining 10% of the decrease in sediment load is a result of the operation of
reservoirs in the upper reaches. In the lower reaches, 20% of the sediment passing Huayuankou has been lost as a result of channel
deposition and water abstraction. Soil conservation practices and the operation of reservoirs have lowered the content of coarser sediment
(DN0.05mm) at Huayuankou, and reduced channel deposition in the lower reaches. In contrast, sediment loss owing to water abstraction
in the lower reaches has increased considerably as water consumption for agricultural needs has increased. Therefore, the combined
effects of climate change and human activities in the upper, middle, and lower reaches have resulted in stepwise decreases in the sediment
load delivered from the Huanghe to the sea. The Huanghe provides an excellent example of the altered river systems impacted by climate
change and extensive human activities over the past 56 yr. Further dramatic decreases in sediment load and water discharge in the
Huanghe will trigger profound geological,morphological, ecological, and biogeochemical responses in the estuary, delta, and coastal sea.

Keywords: Huanghe (Yellow River); stepwise decrease; sediment load; climate change; human activity; dam and reservoir


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