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    黄土高塬沟壑区塬面识别及产沙情势评价

    Identification of tableland and evaluation of sediment yield in the Loess tableland gully area

    • 摘要: 为研究黄土高塬沟壑区的产沙情势,以塬面集中分布的20个水文单元为研究区,引入破碎度指数(Meff)评价塬面破碎程度,分析Meff与产沙量的关系,构建黄土高塬沟壑区产沙模型。Meff≥100为完整塬;50≤Meff<100为墚塬;Meff<50为残塬。Meff与实际产沙/丘陵区模型产沙呈线性高度负相关,决定系数R2为0.9649,由此建立基于Meff的黄土高塬沟壑区产沙模型。2025、2030、2035和2050年黄土高塬沟壑区Meff值大于50塬面较完整区域产沙总量与2018年相比,减幅分别为8.38%、14.66%、19.85%和31.44%,2025年至2050年产沙模数和产沙量变化不显著,梯田林草规模如布设在黄土丘陵沟壑区,产沙量减幅分别可高达13.2%、22.30%、29.65%和45.08%。黄土高塬沟壑区梯田林草的减沙效果明显低于黄土丘陵沟壑区,保护塬面、阻止径流集中下沟和雨洪高效集蓄利用技术是未来治理及研究的方向。研究结果对塬区水土流失防治、重大工程决策、水沙变化研究等具有重要意义。

       

      Abstract: BackgroundSince 2000, the amount of sediment from the Yellow River has significantly decreased. The average annual sediment yield at Tongguan Hydrological Station has decreased from 1.344 billion tons before 2000 to 245 million tons between 2000 and 2019, a decrease of 81.79%. More than 90% of the sediment in the Yellow River comes from the loess hilly gully area and the loess tableland gully area, and there is a significant difference in the reduction of sediment inflow between the two regions.Methods To study the sediment yield situation in the loess tableland gully region, The 20 hydrological units concentrated on the loess tableland gully area were selected as the study area. The fragmentation index (Meff) was introduced to evaluate the degree of tableland fragmentation, and the relationship between Meff and sediment yield was analyzed to construct a sediment yield model for the loess tableland gully area.Results Meff ≥ 100 is considered a complete tableland,50 ≤ Meff < 100 is a hilly tableland(Slightly fragmentized tableland),Meff < 50 is considered a fragmentized tableland.Meff is highly negatively correlated with the actual measured sediment yield/the sediment yield calculated using sediment yield model in the Loess hilly gully area, with a coefficient of determination R2 of 0.9649.Based on this, established a Meff based sediment yield model for the loess tableland gully area. In 2025, 2030, 2035, and 2050, the total sediment yield of tablelands with Meff values greater than 50 will decrease by 8.38%, 14.66%, 19.85%, and 31.44% respectively compared to 2018. There is no significant change in sand production modulus and sediment yield from 2025 to 2050. If terraced fields and forests and grasslands are deployed in the loess hilly gully area, the reduction in sediment yield can be as high as 13.2%, 22.30%, 29.65%, and 45.08%, respectively.ConclusionThe sand reduction effect of terraced fields and forest grasslands in the loess tableland gully area is significantly lower than that in the loess hilly gully area.Protecting the surface of the tablelands, preventing the concentration of runoff into the ditch, and implementing efficient rainwater harvesting and utilization technologies are the directions for future governance and research.The research results are of great significance for the prevention and control of soil erosion, major engineering decision-making, and the study of water and sediment changes.

       

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