【摘要】：退耕還林工程不僅可以提升流域的水土保持功能,還可以恢復流域水源涵養(yǎng)功能,具有極為顯著的生態(tài)效益。從1999年開始,我國實施了大面積地退耕還林還草這一重大生態(tài)工程,其中,黃土高原是該工程重點實施區(qū)。為定量評估退耕還林工程對流域水土保持功能和水源涵養(yǎng)功能的作用,重點對黃土高原延河、北洛河、無定河、窟野河和涇河五個典型流域植被變化與流域水沙過程變化響應關系進行了分析。主要研究結果如下：(1)用歸一化植被指數(shù)(NDVI)表征植被變化,研究黃土高原典型流域植被覆蓋時空變化。工程實施后的2000-2010年,延河、北洛河、無定河三個流域NDVI均隨時間呈上升趨勢,北洛河增幅最大,各流域NDVI最大值出現(xiàn)時間均在2007-2009年；(2)五個流域降水量變化趨勢不顯著,其中窟野河、涇河和延河呈上升趨勢,無定河和北洛河呈下降趨勢,北洛河降水波動最大；除無定河外,其他四個流域徑流量呈下降趨勢,其中窟野河下降趨勢顯著,涇河、北洛河年際波動較大；五個流域輸沙量均呈下降趨勢,其中窟野河、北洛河下降趨勢顯著,各流域輸沙年際波動較大；黃土高原典型流域徑流總量占黃河總徑流量的比例從13.1%減少到8.2%,呈不顯著下降趨勢。延河1980-2010年降水量、徑流量和輸沙量均成下降趨勢,其中徑流輸沙下降趨勢顯著,利用Mann-Kendall法確定2003年為水文序列分界點,將30年劃分為前期(1980-2002年)和退耕還林影響期(2003-2010年)；(3)通過分析工程實施以來徑流系數(shù)年際變化、同一流域不同時間段降水-徑流關系、不同NDVI的流域降水-徑流關系,定性分析退耕還林工程對流域降水-徑流關系的影響。研究結果表明,五個流域徑流系數(shù)均成下降趨勢；延河前期降水-徑流關系相關性較好,退耕還林影響期降水-徑流關系相關性性不顯著,同等年降水量情況下,退耕還林影響期年徑流量下降0.87×108m3,退耕還林工程削弱降水-徑流關系,減少流域產流；隨著NDVI增加,無定河、延河和北的洛河降水-徑流相關性依次減小,在相似降水條件下,無定河、北洛河和延河徑流量依次減少,說明植被覆蓋增加削弱降水-徑流關系,減少流域產流；(4)為量化退耕還林工程對流域產流產沙的影響,以2000年為始,擬合流域NDVI與流域相應年份徑流系數(shù)、輸沙量的關系。結果表明NDVI與徑流系數(shù)、輸沙量呈負相關,通過顯著性檢驗(α=0.05)。本研究為流域水土保持措施實施和干旱地區(qū)水資源可持續(xù)利用提供科學依據(jù),完善研究人類活動對流域徑流產沙作用的理論和方法,有利于政策后續(xù)評價。
[Abstract]:The project of returning cropland to forest can not only improve the function of soil and water conservation, but also restore the function of water conservation. Since 1999, China has carried out a major ecological project of returning farmland to forest and grassland in a large area, among which, the Loess Plateau is the key implementation area of the project. In order to evaluate quantitatively the effects of conversion of cropland to forest on soil and water conservation function of watershed, the emphasis is placed on Yanhe, Beiluo River and Wuding River in the Loess Plateau. The relationship between vegetation change and water and sediment process in five typical watersheds of Grotto River and Jinghe River was analyzed. The main results are as follows: (1) the change of vegetation was characterized by normalized vegetation index (NDVI), and the temporal and spatial changes of vegetation cover in typical watershed of Loess Plateau were studied. From 2000 to 2010 after the implementation of the project, the NDVI of Yanhe, Beiluo and Wuding rivers all showed an upward trend with time, the increase of NDVI in North Luohe River was the largest, and the maximum value of NDVI in each watershed appeared in 2007-2009. (2) the change trend of precipitation in the five basins is not significant, among which the Grotto River, Jing River and Yanhe River show an upward trend, Wuding River and North Luohe River show a downward trend, and the North Luohe River has the largest fluctuation of precipitation; Except the Wuding River, the runoff of the other four watersheds showed a downward trend, in which the Grottoes River decreased significantly, the Jinghe River and the North Luohe River fluctuated greatly. The sediment transport in the five watersheds showed a decreasing trend, among which the Grottoes River and the North Luohe River showed a significant downward trend, and the interannual fluctuation of sediment transport in each watershed was quite large. The proportion of total runoff to the total runoff of the Yellow River decreased from 13.1% to 8.2% in the Loess Plateau, showing no significant decline trend. The precipitation, runoff and sediment discharge of Yanhe River from 1980 to 2010 showed a decreasing trend, among which runoff and sediment transport showed a significant downward trend. The Mann-Kendall method was used to determine that 2003 was the boundary point of hydrological series. Divide 30 years into early period (1980-2002) and period of returning cropland to forest (2003-2010); (3) by analyzing the interannual variation of runoff coefficient since the implementation of the project, the relationship between precipitation and runoff in different time periods in the same watershed, and the relationship between precipitation and runoff in different NDVI watershed, the effect of returning cropland to forest project on the relationship between precipitation and runoff is analyzed qualitatively. The results show that the runoff coefficients of the five watersheds are in a downward trend. The relationship between precipitation and runoff was good in the early stage of Yanhe River, and the correlation between precipitation and runoff was not significant in the period of returning cropland to forest. Under the same annual precipitation, the annual runoff decreased by 0.87 脳 108m3 during the period of returning cropland to forest. The project of returning cropland to forest weakens the relationship between precipitation and runoff and reduces runoff production in the watershed. With the increase of NDVI, the correlation between precipitation and runoff in Wuding River, Yanhe River and Luohe River in the north decreased in turn. Under similar precipitation conditions, the runoff of Wuding River, Beiluo River and Yanhe River decreased in turn, indicating that the increase of vegetation cover weakens the relationship between precipitation and runoff. Reducing runoff production; (4) in order to quantify the effect of returning cropland to forestry project on runoff and sediment yield in watershed, the relationship between NDVI and runoff coefficient and sediment transport in corresponding year of watershed was fitted from 2000 to 2000. The results showed that NDVI was negatively correlated with runoff coefficient and sediment transport, and was significantly tested (偽 = 0. 05). This study provides a scientific basis for the implementation of soil and water conservation measures and the sustainable utilization of water resources in arid areas, and improves the theory and method of studying the effect of human activities on runoff and sediment in river basins, which is beneficial to the policy follow-up evaluation.
【學位授予單位】：中央民族大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：S157

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本文編號：2405946