Abstract: | Soil erosion and lake sediment loading are primary concerns of watershed managers
around the world. In the Xinjiang River Basin of China, severe soil erosion occurs primarily during
monsoon periods, resulting in sediment flow into Poyang Lake and subsequently causing lake water
quality deterioration. Here, we identified high-risk soil erosion areas and conditions that drive
sediment yield in a watershed system with limited available data to guide localized soil erosion
control measures intended to support reduced sediment load into Poyang Lake. We used the Soil
and Water Assessment Tool (SWAT) model to simulate monthly and annual sediment yield based on
a calibrated SWAT streamflow model, identified where sediment originated, and determined what
geographic factors drove the loading within the watershed. We applied monthly and daily streamflow
discharge (1985–2009) and monthly suspended sediment load data (1985–2001) to Meigang station
to conduct parameter sensitivity analysis, calibration, validation, and uncertainty analysis of the
model. The coefficient of determination (R
2
), Nash–Sutcliffe efficiency (NSE), percent bias (PBIAS),
and RMSE -observation’s standard deviation ratio (RSR) values of the monthly sediment load were
0.63, 0.62, 3.8%, and 0.61 during calibration, respectively. Spatially, the annual sediment yield rate
ranged from 3 ton ha−1year−1 on riparian lowlands of the Xinjiang main channel to 33 ton ha−1year−1
on mountain highlands, with a basin-wide mean of 19 ton ha−1year−1
. The study showed that 99.9%
of the total land area suffered soil loss (greater than 5 ton ha−1year−1
). More sediment originated
from the southern mountain highlands than from the northern mountain highlands of the Xinjiang
river channel. These results suggest that specific land use types and geographic conditions can be
identified as hotspots of sediment source with relatively scarce data; in this case, orchards, barren
lands, and mountain highlands with slopes greater than 25◦ were the primary sediment source areas.
This study developed a reliable, physically-based streamflow model and illustrates critical source
areas and conditions that influence sediment yield. |