Geology Reference
In-Depth Information
12
Evaluating Effects of Soil
and Water Management and Land
Use Change on the Loess Plateau
of China using LISEM
R. HESSEL
1
, V.G. JETTEN
2
, B. LIU
3
AND Y. QIU
3
1
Soil Science Centre, Alterra, Wageningen University and Research Centre,
Wageningen, The Netherlands
2
Department of Earth Systems Analysis, International Institute of Geoinformation Science
and Earth Observation, Enschede, The Netherlands
3
School of Geography, Beijing Normal University, Beijing, China
12.1 Introduction
the hilly part of the Loess Plateau. Jiang
et al
.
(1981) estimated that erosion rates may be as
much as 18,000 t km
−2
y
−1
for the hilly loess
region of the Wuding catchment. Sediment con-
centrations in runoff on the Loess Plateau of
over 1000 g l
−1
have been recorded regularly
(Jiang
et al
., 1981; Zhang
et al
., 1990; Wan &
Wang, 1994). There are several reasons for these
very high erosion rates:
●
The loess is very erodible, especially when wet.
●
The area's rainfall is characterized by heavy
storms in summer (mainly July and August).
Single storms can produce 10% of yearly precipi-
tation and 40% of erosion (Gong & Jiang, 1979;
Zhang
et al
., 1990). Although the saturated con-
ductivity of the loess is generally higher than
rainfall intensity, crusting prevents the water
from infiltrating (Douglas, 1989).
●
The area has considerable relief.
●
Vegetation cover is generally sparse. This is
partly caused by a semi-arid climate with cold
winters, but also by removal of the natural vege-
tation and by grazing (Jiang
et al
., 1981).
In 1999, the Chinese government formulated
new ambitious policies about the Loess Plateau.
These policies aim to decrease erosion rates
through changes in land use (McVicar
et al
.,
2007). In particular, they aim at a large decrease
The Yellow River is China's second largest river
and derives its name from the sediment sus-
pended in its waters. These sediment contents
pose a major problem because sedimentation in
the lower course of the river has raised the river
bed to several metres above the surrounding land-
scape, and because reservoirs are being filled with
sediment. The Chinese government is commit-
ted to combating these problems. Much attention
is being directed at decreasing the erosion rates
on the Loess Plateau, since this is the source of
about 90% of all the sediment that enters the
Yellow River (Douglas, 1989; Wan & Wang, 1994).
Lowering the erosion rates should decrease down-
stream sedimentation problems, and at the same
time reduce the loss of agricultural land on the
Loess Plateau itself.
The Loess Plateau has some of the highest
erosion rates on Earth, especially in the so-
called hilly part, which is heavily dissected by
gullies. Plate 8 shows a typical landscape for
