基于SWAT模型的白龙江流域生态修复效应模拟研究

发布时间：2018-06-03 15:23

本文选题：SWAT模型 + 生态修复　；参考：《兰州大学》2015年硕士论文

【摘要】：白龙江流域是我国水土流失严重和泥石流灾害高发地区之一,生态修复是改善白龙江流域脆弱生态环境、防治水土流失和泥石流灾害的重要手段,对不同生态修复模式的修复效应进行模拟研究是该流域开展生态修复的重要科学依据。本文选用基于物理机制的SWAT分布式水文模型及其情景模拟法,从地表生态水文过程的角度出发,选用地表径流深度这一关键指标,对不同生态修复模式下白龙江流域径流变化进行了模拟分析,并进一步以白龙江流域典型泥石流沟——构林坪小流域为例,基于泥石流启动的地表径流深度阈值,分析了不同生态修复方式对该流域泥石流灾害的防灾减灾效应。主要结论如下：(1) SWAT模型适用于白龙江流域。通过对白龙江流域中游武都水文站和下游碧口水文站的流量进行率定和验证,效率系数和相关系数均达到了SWAT模拟的基本要求,能够客观准确地模拟白龙江流域地表径流深度以及径流量。(2)通过SWAT模型参数的敏感性分析,得到对白龙江流域的径流有较大影响的参数,主要包括CN2(径流曲线系数)、SURLAG(地表径流滞后系数)、CH K2(主河道水力传导率)等。(3)白龙江流域的泥石流灾害生态修复效应模拟。本文以国家退耕还林还草政策为基础设计了35种生态修复模式(情景),包括5种极端模式(情景)和30种合理模式(情景)。(4)分析了5种极端模式下的流域年均地表径流深度变化情况,结果显示,全部耕地退耕为常绿林的生态修复情景对降低该流域地表径流深度最为有效,下降率达到12.79%,生态修复效果最佳。然后从月时间尺度分析了极端情景下的月均地表径流深度变化情况,与基准情景的地表径流深度相比,各极端情景的地表径流深度为全年整体下降,没有出现个别月份地表径流深度上升的情况,说明本模拟结果具有较高的准确度。(5)分析了30种合理情景下的白龙江流域年均地表径流深度变化情况。结果显示：在退耕后植被类型相同时,对坡度大于15度耕地进行退耕,其对地表径流深度的减少程度次于耕地全部退耕的极端情景,但是高于坡度大于25度耕地退耕的情景。结合退耕面积进行分析,结果显示,对坡度大于15度的耕地进行退耕的修复情景减少地表径流深度的效率最高,以退耕为常绿林的情景为例,平均每退耕1km2耕地,流域地表径流深度下降0.0095mm。最后分析了不同坡度级别退耕不同植被类型的情景,结果显示,退耕类型为常绿林和灌丛的组合时,地表径流深度下降幅度最大。(6)构林坪流域的泥石流灾害生态修复效应模拟。以国家退耕还林还草政策为基础,结合流域的自然植被的分布规律,设计了9种生态修复模式(情景)。分析各情景下的年均地表径流深变化情况,结果显示,对构林坪小流域而言,耕地退耕为林地的修复情景效果最明显,年均地表径流深度下降了21.15%,其次是林地与灌丛的组合修复情景。(7)根据研究所得的构林坪流域泥石流启动降水阂值以及2013年构林坪泥石流沟灾害的历史记录,得到构林坪泥石流沟泥石流启动的地表径流深度阈值为9.49mm。(8)基于地表径流深度阂值,以2013年5月24日发生泥石流灾害为基准,模拟了不同生态修复情景下构林坪泥石流沟的地表径流深度的变化特征,结果显示,本文设计的9种生态修复情景均能够使地表径流深度降低到地表径流深度阂值以下,其中耕地退耕为林地和灌丛的生态修复情景降低幅度最大,说明人类可以通过生态修复工程遏制泥石流的启动,降低灾害发生的几率,从而有效地防治泥石流灾害。
[Abstract]:The white Longjiang basin is one of the regions with high soil erosion and debris flow disasters in China. Ecological restoration is an important means to improve the fragile ecological environment in the white Longjiang River Basin and prevent and control soil erosion and debris flow. The simulation of the restoration effects of different ecological restoration patterns is an important scientific basis for the ecological restoration in this basin. In this paper, the SWAT distributed hydrological model based on physical mechanism and its scenario simulation method are selected. From the angle of the surface ecological hydrological process, the key index of surface runoff depth is selected, and the runoff changes in the white Longjiang basin under different ecological restoration models are simulated and analyzed, and the typical debris flow gully in the white Longjiang basin is further studied. As an example, based on the threshold of surface runoff depth initiated by debris flow, the effects of different ecological restoration methods on the disaster mitigation of debris flow in this basin are analyzed. The main conclusions are as follows: (1) the SWAT model is suitable for the white Longjiang basin. The flow of the flow into the Wudu hydrological station in the middle reaches of the white Longjiang River Basin and the downstream Bi Kou hydrologic station. Line rate determination and verification, efficiency coefficient and correlation coefficient all meet the basic requirements of SWAT simulation, and can objectively and accurately simulate the surface runoff depth and runoff in the white Longjiang basin. (2) through the sensitivity analysis of SWAT model parameters, the parameters of the runoff in the white Longjiang basin are greatly affected, including CN2 (runoff curve coefficient), S URLAG (surface runoff lag coefficient), CH K2 (main channel hydraulic conductivity) and so on. (3) simulation of the ecological restoration effect of debris flow disaster in the white Longjiang basin. This paper designs 35 ecological restoration models based on the national policy of returning farmland to forest and grass, including 5 kinds of extreme patterns (scenarios) and 30 reasonable patterns (4) analysis of 5 extremes The results show that the ecological restoration scenario of returning farmland to the evergreen forest is the most effective for reducing the surface runoff depth of the basin, the decline rate is 12.79%, and the ecological restoration effect is the best. Then the monthly average surface runoff depth changes under the extreme situation are analyzed from the monthly time scale. Compared with the surface runoff depth of the baseline scenario, the surface runoff depth of the extreme scenarios fell throughout the year, and there was no rise in the surface runoff depth in a few months, indicating that the simulation results had higher accuracy. (5) the annual surface runoff depth changes of the white Longjiang basin under the 30 reasonable scenarios were analyzed. The results showed that when the vegetation types were the same after the conversion of ploughing, the slope of cultivated land was lower than 15 degree farmland, and the degree of reducing the depth of surface runoff was lower than that of all the arable land. But it was higher than the situation that the slope was more than 25 degrees. The efficiency of reducing the depth of surface runoff was the highest. Taking the scenario of returning farmland to evergreen forest, an average of 1km2 cultivated land was taken as an example. The depth of surface runoff decreased by 0.0095mm. in the basin. Finally, the situation of different vegetation types at different slope grades was analyzed. The results showed that the surface runoff was the surface runoff when the tillage type was the combination of the evergreen forest and the shrub. The maximum depth decreased. (6) simulation of the ecological restoration effect of debris flow disaster in the construction of Lin Ping basin. Based on the national policy of returning farmland to forest and grass, combined with the distribution law of natural vegetation in the basin, 9 ecological restoration models were designed. In the domain, the effect of cultivated land restoration for forest land was the most obvious, and the annual surface runoff depth decreased by 21.15%, followed by the combination restoration situation of woodland and shrub. (7) according to the study on the starting precipitation of the debris flow in the construction of the forest plateau and the historical records of the debris flow gully in 2013, the debris flow gully of the forest floor was constructed. The depth threshold of surface runoff started by debris flow is 9.49mm. (8) based on the depth of surface runoff. Based on the debris flow disaster in May 24, 2013, the change characteristics of surface runoff depth in the debris flow gully of different ecological restoration scenarios are simulated. The results show that the 9 ecological restoration scenarios designed in this paper can make the surface of the earth surface. The depth of runoff is reduced to below the depth of surface runoff, and the ecological restoration scenario of cultivated land and shrub has been reduced to the greatest extent. It shows that human can control the start of debris flow through ecological restoration project, reduce the probability of disaster and effectively prevent and control the debris flow disaster.
【学位授予单位】：兰州大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X171.4

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