Soil erosion and its spatial distribution in the Three-River-Source National Park
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Monitoring Center of Soil and Water Conservation, Ministry of Water Resources

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S157

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    Abstract:

    [Objective] Three-River-Source National Park (TRSNP), which comprises the headwaters of the Yellow, Yangtze and Mekong Rivers, has been described as the ‘Water Tower of Asia’. It is of great importance to explore and analyze the spatial distribution characteristics of soil erosion in the TRSNP. [Methods] Water erosion of the park was assessed using the Chinese Soil Loss Equation (CSLE) integrating rainfall erosivity factor (R) acquired using the daily rainfall data of 5 counties including Zhiduo, QuMalai, Maduo, Zaduo and Tanggula county in Qinghai province during 1986-2015, soil erodibility factor (K) obtained from the First National Water Census for Soil and Water Conservation published by Ministry of Water Resources, P.R.China in 2013, slope length factor (L) and slope steepness factor (S) extracted from the 1:50,000 topographic map, biological control factor (B) estimated by vegetation coverage, and the values of engineering control factor (E) and tillage factor (T) assigned according to the related outcome of the First National Water Conservancy Census. Wind erosion of the TRSNP was evaluated by grass-shrub wind erosion model and sandy-land wind erosion model considering wind erosivity factors based on wind speed during 1991-2015, topsoil moisture factors calculated by AMSR-E level 2A brightness temperature, roughness factors and vegetation coverage. Takes phase transition water content, freeze-thaw cycle days, annual precipitation, slope, slope aspect, vegetation coverage as indexes to evaluate freeze-thaw erosion intensity. [Results] The results showed that the area of 2.64×104km2 suffered from soil erosion, accounting for 21.47% of land area in TRSNP. Among the three sub-parks, the Yellow-River-Source Park possessed with the most extensive soil erosion, in which soil erosion accounting for approximately 50% of the total land areas, twice than that of the TRSNP, whereas one-eighth of the Yangtze-River-Source Park area subject to extremely severe erosion. The elevation in the TRSNP along with the degree of slope, as well as depleted grassland cover were major factors in soil erosion. Water erosion occurred mainly in the area with elevations above an elevation of 4900 m, which occupied 70% of the land area, however, 85% of the wind erosion occurred in zones less than 4900m in elevation. The water erosion areas were mainly located in regions where the slope categories were 8°-25°, and a major part of the wind erosion were widely distributed in slopes between 0° and 5°, all of that needed urgent conservation measures. Grassland was the most important land cover in the TRSNP, which occupied about 80% of the area. Scenarios with different vegetation cover on soil erosion areas showed that low vegetation cover (<30%) and medium-low cover (30%-45%) can considerably caused the loss of soil erosion. Besides, it is worth noting that sandy land and bare land prone to high intensity soil erosion. [Conclusion] In general, Two-thirds of water erosion areas were mainly distributed in zones where the elevation was above 4900m, slope gradients between 8° and 35°, and grassland cover less than 45%. Wind erosion was particularly distributed in an elevation ranging from 4200m to 4900m, the degree of slope less than 5°, and grassland coverage less than 60%. The spatial distribution of soil erosion varied greatly among the sub-areas, demonstrating partition policy should be considered to reduce soil erosion. The present results provide a vital database necessary to control soil erosion in order to ensure sustainable ecological civilization construction in the TRSNP.

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History
  • Received:July 25,2023
  • Revised:August 23,2023
  • Adopted:August 26,2023
  • Online: November 01,2023
  • Published: