小流域水土流失治理优先度的评价与应用

    Evaluation and application of the management priority of soil erosion in small watersheds

    • 摘要: 中国水土流失防治任务仍然繁重,有计划分批次实施水土流失治理是现阶段条件下的必然选择,优先治理小流域识别是其首要解决的一项基础工作,然而目前相关成果较为缺乏,难以支撑小流域水土流失治理智能决策和精准施策。在当前大力推进智慧水土保持背景下,积极探索优先治理小流域识别方法非常迫切,对于科学、合理、高效促进水土流失治理工作具有重要意义。该研究立足于小流域自然禀赋条件,以中国水土流失重点区域——三峡库区秭归县为例,坚持科学性和可操作性相结合原则,以水土流失“减量和降级”双重目标和治理效益最大化需求为导向,综合水土流失面积和土壤侵蚀强度两个维度,提出小流域水土流失治理优先度定义及定量评价方法,为识别优先治理小流域提供科学依据和技术支撑。结果显示,秭归县2021年现状水土保持率为69.12%,远期(2050年)水土保持率为81.74%,总体提升12.62个百分点。秭归县2021年全域土壤侵蚀模数现状为758.50 t/(km2·a),最小可能土壤侵蚀模数为408.71 t/(km2·a),总体下降比例达46%。秭归县大部分区域均具有较大的水土保持率提升潜力和土壤侵蚀控制度,可完全治理和可降级的水土流失地块分布较为广泛,尤其在县域中西部的小流域存在较大的水土流失面积消减和土壤侵蚀强度降级空间。秭归县各小流域水土流失治理优先度的空间分布总体呈现中部高,东部和南部相对较低的分布格局,全县治理优先度大于0.6的小流域占总全县小流域的11.76%。通过典型县应用,该研究提出的小流域治理优先度涵盖了水土流失面积和土壤侵蚀强度两个维度,能更为全面满足小流域水土流失“减量和降级”双重目标和和治理效益最大化需求,直观反映了水土流失面积消减空间和土壤侵蚀强度降级空间的目标和相对大小,对支撑小流域治理决策更加准确、科学,治理优先度评价方法不仅可行,且易操作。

       

      Abstract: Soil erosion has caused a heavy threat to agriculture production in China at the present stage. The accurate identification of priority small watersheds is one of the most important tasks for implementing control and prevention in batches. However, it is still lacking in the intelligent decision-making and implementation of soil loss control at present. Among them, the severity of soil erosion is an important indicator of priority small watersheds. Previous studies have been focused on the simple and single indicator during evaluation and consideration. Many subjective factors have also made the evaluation complex and less accessible. Therefore, it is very urgent to identify the management priority for the scientific, reasonable, and efficient application of soil loss control for better conservation. This study aims to evaluate the management priority of soil erosion control in small watersheds. The key area of soil erosion was selected at Zigui County in the Three Gorges Reservoir Area. The double goals were taken as the 'reduction and degradation 'of soil and water loss. Two dimensions were also integrated with the soil and water loss area and soil erosion intensity. The results show that the current soil and water conservation rate in 2021 was 69.12%, and the long-term (in 2050) soil and water conservation rate was 81.74%, with an overall increase of 12.62 percentage point. The soil erosion modulus in 2021 was 758.50 t/(km2·a) at present, where the minimum modulus of soil erosion was 408.71 t/(km2·a) with an overall decline ratio of 46%. However there were great differences among the soil and water conservation rates under current and long-term situations, as well as the current and the minimum soil erosion modulus in each small watershed. The long-term soil and water conservation rate and the minimum soil erosion modulus were generally similar to the spatial distribution, compared with the current. But there were great changes in some areas and values. Most areas shared a large potential for the soil and water conservation rate, as well as the soil erosion control degree. Erosion plots were widely distributed to be completely managed and downgraded, especially in the small watersheds in the central and western parts of the county. Large areas were found for the soil erosion area abatement and soil erosion intensity downgrading. The spatial distribution pattern was observed in the priority of soil erosion control in each small watershed: high in the central part, while relatively low in the eastern and southern parts. The number of small watersheds with a management priority greater than 0.6 accounted for 11.76% of the total. The management priority can be expected to cover both soil erosion area and soil erosion intensity. The goals and the relative size were determined for their reduction space. An accurate and rapid detection can also be achieved for the decision-making on the small watershed. The finding can provide technical support to identify the priority of soil corrosion in small watersheds.

       

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