【摘要】：河流攜帶泥沙注入海洋是生物地球化學循環(huán)重要一環(huán),是全球剝蝕系統(tǒng)關鍵組成部分,也是評估土地退化和全球土壤資源減少重要度量。研究全球河流輸沙量的變化對研究陸地的表面過程、及陸地海洋系統(tǒng)物質循環(huán)(如,碳循環(huán))具有重要的意義。全球尺度研究河流輸沙量空間分布格局和時序變化及其二者的影響因素可以揭示河流輸沙的一般規(guī)律,對認識人類活動對河流輸沙量的影響也具有重要意義。近50年,在氣候變化和人類活動日益增強的背景下,全球眾多河流輸沙量都發(fā)生顯著變化。研究人員以區(qū)域河流為研究對象,解釋了河流輸沙量在時間尺度上的時序變化及其影響因素。但從全球尺度進行河流輸沙量的研究卻較少,全球河流輸沙量空間分布格局及其影響因素在國外才初步展開。本文以全球657條入海河流為研究對象,利用數(shù)理統(tǒng)計和空間分析方法對全球河流輸沙量的空間分布格局進行了研究;以各氣候區(qū)8條代表性河流為研究對象,利用數(shù)理統(tǒng)計方法對其時序變化及其影響因素進行分析;在此基礎上,基于過去各影響因素的時序變化,對未來全球河流輸沙量進行定性預測。具體研究結果如下:(1)全球河流總輸沙量估計值在1.5—2.0×10~(10) t左右。由于河流輸沙本身的非平穩(wěn)特性和空間差異性,這樣的估值需要謹慎地接受。整體而言,亞洲河流年均輸沙量最大,占全球總輸沙量的一半以上,然后依次是大洋洲、南美洲、北美洲、非洲和歐洲。(2)對河流輸沙量空間分布影響因素分析表明:降水量與輸沙模數(shù)無明顯相關性,徑流量與輸沙量呈顯著線性相關;將流域按徑流深度進行分區(qū)后,濕潤區(qū)(徑流深度750mm/a)徑流量與輸沙量的相關性達0.99�？傮w而言,河流輸沙量隨著流域面積的增大而增加,但相同流域面積的河流輸沙量差別很大;按地形、地質條件對流域進行分區(qū),定性的分析表明高山比低地河流年輸沙量高出1~3個數(shù)量級;新生界地層占主導的流域的年輸沙量要高于前中生界流域。(3)采用Mann-Kendall趨勢檢驗法和線性回歸對各氣候區(qū)8條代表性流域降水、徑流和輸沙時序變化進行研究,分析結果表明:寒帶和熱帶河流輸沙量呈增加趨勢,其它氣候區(qū)河流輸沙量呈顯著減少趨勢;除了熱帶2條河流輸沙量時序變化不顯著外,其余河流輸沙量時序變化極顯著。各流域的降水雖有變化,但均未達到顯著水平p0.05;除黃河和密西西北河外,其余河流徑流量時序變化均不顯著;密西西北河徑流量呈顯著增加趨勢,而其輸沙量卻呈極顯著減少趨勢。因此,河流輸沙量受氣候變化的影響不顯著。相比較而言,人類活動對河流輸沙量的變化影響更大,尤其是壩庫建設。初步的估計表明全球大壩攔截的泥沙量可達4.4×10~(10) m3,這是全球入海泥沙量的2倍多。因此,在研究河流輸沙量變化時要明確地把壩庫作為一個影響因素進行分析。發(fā)展中國家因毀林開荒、采礦或城市化,流域土地利用有較大的變化,導致河流輸沙量顯著增加。(4)相比降水量趨勢性變化,氣候變化導致的極端降水事件對其河流輸沙量的影響更大,研究人員仍需對極端降水事件預測及其環(huán)境效應進行深入研究。局部地區(qū)毀林開荒、采礦、城市化建設導致的土地利用變化會導致河流輸沙量的增加,這些地區(qū)主要集中在發(fā)展中國家,尤其是非洲和南美洲的國家。但由于大規(guī)模壩庫建設,未來全球河流總輸沙量仍將繼續(xù)減少。
[Abstract]:River sediment transport into the ocean is an important part of the biogeochemical cycle, a key component of the global denudation system, and an important measure of land degradation and global soil resource reduction. It is of great significance to study the spatial distribution pattern and temporal variation of river sediment transport and their influencing factors on a global scale, which can reveal the general law of river sediment transport and is of great significance to understand the impact of human activities on river sediment transport. Researchers take regional rivers as the research object to explain the temporal variation of river sediment transport and its influencing factors on time scale. However, there are few studies on river sediment transport on global scale, and the spatial distribution pattern of global river sediment transport and its influencing factors are preliminarily launched in foreign countries. The spatial distribution pattern of global river sediment transport was studied by using mathematical statistics and spatial analysis method, and the temporal variation and its influencing factors of eight representative rivers in each climate area were analyzed by using mathematical statistics method. The results are as follows: (1) The estimated value of global river sediment transport is about 1.5-2.0 *10~ (10) t. Due to the non-stationary characteristics and spatial differences of river sediment transport, such an estimate needs to be cautiously accepted. The largest sediment volume is Oceania, South America, North America, Africa and Europe. (2) There is no significant correlation between precipitation and sediment transport modulus, but there is a significant linear correlation between runoff and sediment transport. The correlation between runoff and sediment transport is 0.99 in the runoff depth of 750 mm/a. Generally speaking, the river sediment transport increases with the increase of the basin area, but the river sediment transport in the same basin area varies greatly. According to the topography and geological conditions, the basin is divided, and the qualitative analysis shows that the annual sediment transport in the mountains is 1-3 more than that in the lowlands. The annual sediment transport in the basins dominated by Cenozoic strata is higher than that in the Pre-Mesozoic basins. (3) Mann-Kendall trend test and linear regression are used to study the temporal variation of precipitation, runoff and sediment transport in eight representative basins in each climatic region. The results show that the sediment transport in cold zone and tropical river is increasing, while that in other climatic regions is increasing. The sediment discharge of the two rivers in the tropics showed a significant decreasing trend, and the sediment discharge of the other rivers changed significantly except for the two tropical rivers. Therefore, river sediment transport is not significantly affected by climate change. In comparison, human activities have a greater impact on river sediment transport, especially on dam and reservoir construction. Therefore, dam and reservoir should be considered as an influencing factor when studying the variation of river sediment transport. Great changes in land use have resulted in a significant increase in river sediment transport in developing countries due to deforestation, mining or urbanization. (4) Compared with the trend change of precipitation, climate change has led to a significant increase in river sediment transport. Extreme precipitation events have a greater impact on river sediment transport. Researchers still need to study the prediction of extreme precipitation events and their environmental effects. Countries in Africa and South America. However, due to large-scale dam and reservoir construction, the global total river sediment transport will continue to decrease in the future.
【學位授予單位】：西北農林科技大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：S157

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