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 (R2), 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.
Highlights
Soil erosion and lake sediment loading are severe ecological and environmental problems that watershed managers face around the world
Our results showed that the Xinjiang River Basin experienced severe soil loss during 1990–2001, with 99.9% of the total land area contributing a sediment yield rate larger than 5 ton ha−1 year−1
The annual sediment yield varied from 3 ton ha−1 year−1 in the lowlands of the two banks of the Xinjiang main river channel to 33 ton ha−1 year−1 in the mountain highlands, with 19 ton ha−1 year−1 on average
Summary
Soil erosion and lake sediment loading are severe ecological and environmental problems that watershed managers face around the world. In subtropical Southeastern China, both climatological and anthropogenic activity have altered hydrology and sediment loading [1]. In these areas, concentrated rainstorms occur during the monsoon period (May–October), where intense regional precipitation likely. Land use change is often identified as a manageable primary factor in soil erosion [4]. To address these erosion problems, managers often rely on modeling tools, but limited data availability discourages the application of many of the most accepted tools due to concerns regarding calibration and validation, which can prevent determination for focused land use management. Many physically-based hydrological models have been developed, such as the Areal NonPoint Source Watershed Environmental Response Simulation (ANSWERS) [5], the Agricultural Nonpoint Source Pollution Model (AGNPS) [6], the Better Assessment Science
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