Spatiotemporal evolution of ecological vulnerability in the Yellow River Basin under ecological restoration initiatives

Optimisation of reservoir operation mode to improve sediment transport capacity of silt-laden rivers

Water erosion is one of the main types of soil degradation, but few quantitative estimates have been done in the soil erosion intensity grades of different landscape scaling characteristics in a large-scale ecological restoration watershed. This study comparatively illustrates the utility of high-resolution data and geospatial technique, particularly the GIS-based RUSLE model, for an improved understanding of the spatial patterns of soil erosion under different land use types, geomorphological styles, vegetational regionalizations, and geographical zonings, aiming to promote ecological sustainable watershed management in practice. Results indicate the following: (i) The soil erosion intensity grade showed an overall decreasing trend from northwest to southeast in the Jinghe River Watershed. The percentages of intense erosion and extremely intense erosion in different land use types in 2015 were significantly lower than that in 2000 except middle- and low-coverage grasslands because of the effective implementation of “Grain for Green” project. e.g., the percentage of extremely intense erosion in dry land decreased from 41.72% in 2000 to 8.99% in 2015. (ii) The mid-elevation loessial beams and hills and mid-elevation loessial tableland were both the major sources of intense erosion and extremely intense erosion, with the contribution ratio of 41.89 and 53.94% and 35.79 and 20.83% in 2000 and 44.45 and 48.99% and 36.88 and 18.72% in 2015, respectively. (iii) The intense, extremely intense and severe erosion in the temperate typical grassland subzone accounted for 32.62, 44.47, and 9.6% in 2000 and 36.74, 40.7, and 8.1% in 2015, respectively. There were no severe and extremely intense erosion in the deciduous oak forest subzone of northern and southern warm temperate. (iv) The intense, extremely intense, and severe erosion of the loessial wide valley hills accounted for 32.19, 45.27, and 8.92% in 2000 and 36.32, 41.42, and 7.48% in 2015. The intense and extremely intense erosion of the loessial tableland accounted for 40.58 and 16.02% in 2000 and 40.57 and 14.27% in 2015. More importantly, land use types can be applied to the design and implementation of a development scheme more reliably than other landscapes because the land use system is a more scientific and fine classification based on topography, soils, and vegetation correlated with geology, geomorphology, and climate. The knowledge on the fine landscape scale will be useful for comprehensive watershed management by soil scientists, agronomists, environmental scientists, land managers, and policymakers.

Landscape scaling of different land-use types, geomorphological styles, vegetation regionalizations, and geographical zonings differs spatial erosion patterns in a large-scale ecological restoration watershed

Assessing the impacts of Grain-for-Green Programme on ecosystem services in Jinghe River basin, China

In this study, a model for the development of the wide floodplain in the lower Yellow River Basin, in China was developed. This model includes flood control schemes using grading criteria, enables sediment deposition in partitioned zones, and allows free exchange between channel runoff and sediment. The wide floodplain located between the main channel and levees is divided into three typical regions: the tender, low, and high floodplains. Different ecological models should be applied when these floodplains are constructed. This paper describes the associated research ideas and methodology, and clarifies several key issues, including sediment prediction and regulation, land planning, land use, and a multi-dimensional framework of safeguard measures for industries on the lower Yellow River floodplain. A refined ecological development model is proposed for the lower Yellow River floodplain, and future work on ecological and sustainable development of the lower floodplain is suggested. To establish a comprehensive system integrating runoff and sediment resource regulation in the Yellow River Basin, future work should focus on runoff and sediment exchange mechanisms in the wandering lower reaches. Furthermore, it is necessary to improve theories on floodplain planning and ecological construction, and these theories should be integrated with the research findings on land development across the lower Yellow River floodplain.

Improved ecological development model for lower Yellow River floodplain, China

The Jinghe River remains the major sediment source of the Yellow River in China; however, sediment discharge in the Jinghe River has reduced significantly since the 1950s. The objective of this study is to identify the causes of sediment yield variations in the Jinghe River Basin based on soil and water conservation methods and rainfall analyses. The results revealed that soil and water conservation projects were responsible for half of the total sediment reduction; sediment retention due to reservoirs and water diversion projects was responsible for 1.3% of the total reduction. Moreover, the Jinghe River Basin has negligible opportunity to improve its vegetation cover (currently 55% of the basin is covered with lawns and trees), and silt-arrester dams play a smaller role in reducing sediment significantly before they are entirely full. Therefore, new large-scale sediment trapping projects must be implemented across the Jinghe River Basin, where heavy rainfall events are likely to substantially increase in the future, leading to higher sediment discharge.

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Yizi Shang

Papers

Causes of Variations in Sediment Yield in the Jinghe River Basin, China.

Optimisation of reservoir operation mode to improve sediment transport capacity of silt-laden rivers

Improved ecological development model for lower Yellow River floodplain, China