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Based on the concept of runoff erosion power, to establish the basin energy-sediment relationship model can provide theoretical support for the accurate simulation of sediment load change and soil and water conservation planning in the Yangtze River Basin. In this study, the typical watersheds of the Yangtze River and its typical small watersheds were taken as the research objects. By collecting the daily precipitation, runoff and sediment data of three typical watersheds including Jinsha River Basin, Jialing River Basin and Xiangjiang River Basin from 1965 to 2018, and the rainstorm flood scale precipitation, runoff and sediment data of two typical small watersheds including Wan 'an and Lizikou from 2014 to 2020, the runoff erosion power and rainfall erosivity were used to compare and analyze the advantages and disadvantages of the relationship between runoff and sediment load, rainfall erosivity and sediment load, and runoff erosion power and sediment load at different spatial and temporal scales. The superiority of the relationship between runoff erosion power and sediment load was analyzed, and the inconsistent changes of the relationship between runoff erosion power and sediment load were identified, so as to improve the model of the relationship between runoff erosion power and sediment load and improve the simulation accuracy of sediment load in the watershed. The results showed that: (1) In most cases, the performance of runoff erosion power and sediment load relationship was always better than that of runoff and sediment load relationship, rainfall erosivity and sediment load relationship in three typical watersheds and two typical small watersheds in the Yangtze River Basin. At the event, monthly, and annual scales, the maximum R 2 adj values can reach 0.94, 0.87, and 0.54, respectively. Sediment load always increased with the increase of runoff, rainfall erosivity and runoff erosion power. (2) For different time scales, the first flow Q1 quantile was always close to 1 and the second flow Q2 quantile was around 0.5 or higher than 0.5 when the correlation between any two flow products and sediment load in the flow sequence was high. Based on the runoff erosion power, the sediment load of watersheds at different spatial and temporal scales can be accurately calculated, which had obvious applicability. (3) With the time upscaling, the relationship between runoff and sediment load, rainfall erosivity and sediment load, and runoff erosion power and sediment load gradually deteriorated. The runoff erosion power and sediment load of the three typical watersheds had significant trends and significant change-points in some months (P<0.05). Especially on the annual scale, the sediment load showed a significant decreasing trend (P<0.05), and the runoff erosion power and sediment load relationship showed inconsistent changes. (4) Reservoir construction and vegetation increase were important reasons for the deterioration of the runoff erosion power and sediment load relationship in the basin, which were significantly negatively correlated with sediment load (P<0.001). By considering the reservoir index and NDVI to improve the runoff erosion power and sediment load relationship model, R 2 can be increased by 27.28%-97.62%. The research results will support the development of new watershed sediment prediction models and serve the ecological protection and high-quality development of the Yangtze River Basin. [ABSTRACT FROM AUTHOR]

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Copyright of China Brewing is the property of China Brewing Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Chongqing University of Technology (Natural Science) is the property of Chongqing University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Research of Soil & Water Conservation is the property of Institute of Soil & Water Conservation, Chinese Academy of Sciences & Ministry of Water Resources and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Rainfall erosivity and vegetation cover are two of the most important factors in regional soil erosion. The greater the rainfall erosivity is, the more favorable the soil erosion is, whereas, the better the vegetation coverage is, the less favorable the soil erosion is. Moreover, the Yangtze River Economic Belt has been a prominent ecological and national strategic area in China. It is of great practical significance to determine the relationship between rainfall erosivity and vegetation cover, in order to protect the ecological environment. In this study, the daily-scale rainfall erosivity model and the Mann-Kendall trend test were applied to analyze the temporal and spatial evolution of monthly-scale rainfall erosivity and NDVI using daily precipitation and monthly NDVI data. The Pettitt test and coupling coordination degree theory were then used to identify the temporal and spatial variation of the coupling coordination relationship between rainfall erosivity and NDVI. Finally, the reasons were proposed for the change of the coupling coordination relationship between them. The results showed that: 1) Multi-year average rainfall erosivity from July to October was evenly distributed in the whole region, while there was a decrease from the southeast to the northwest in the rest months from 1965 to 2019. A significant increasing trend of rainfall erosivity was also found in the eastern region in July and September (P<0.05). The rainfall erosivity in the central region showed a significant decrease in January, whereas, there was a significant increasing in the central and southern regions in March. The rainfall erosivity in the southwest showed a significant decrease trend in May. 2) On a multi-year scale, the NDVI of the whole gradually increased from June to September, and it reached the highest level in August. The ratio of the area where the NDVI increased significantly in different months to the total area of the study area all exceeded 30% (P<0.05) from 1999 to 2019. The regions with the significant NDVI increase were distributed mainly in the southwest, central and southern regions. But, the NDVI in the eastern region decreased significantly, where the soil erosion risk was also high. 3) There was a high multi-year average in the coupling coordination degree of rainfall erosivity and NDVI in the east, but a low in the west. A significant decrease was detected in the coupling coordination degree in the central and southwestern regions, while a significant increase was in the eastern regions (P<0.05). The significant change-points were found in the coupling coordination degree of rainfall erosivity and NDVI, which were distributed mainly in the southwest, central and eastern regions in the occurrence period from 2003 to 2014. 4) The reduction of forest area (such as evergreen coniferous forest, evergreen broad-leaved forest, mixed forest, and closed shrub forest) was the important reason for the significant increase of coupling coordination degree in the east, indicating a high percentage of vegetation cover but a very small percentage of the area. Consequently, it is a high demand to rationally increase the forest land in space pattern for the ecological environment. The finding can greatly contribute to further understanding the risk of soil erosion in the Yangtze River Economic Belt. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Ordnance Equipment Engineering is the property of Chongqing University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study aims to explore the temporal and spatial evolution of rainfall concentration against the global climate change in the Northwest region of China. Mann-Kendall trend test and change-point detection were carried out on a series of monthly raster rainfall data in the Northwest region from 1960 to 2017. Morlet wavelet was also used to analyze the periodic change in rainfall concentration. Moreover, a hotspot analysis was made on the spatial distribution and aggregation characteristics of rainfall concentration. A cross-wavelet analysis was used to explore the relationship between atmospheric circulation factors and rainfall concentration, thereby determining the influence of landform distribution on rainfall concentration. The results showed that: 1) The average rainfall concentration presented a decreasing trend in the Northwest region and the three sub-regions (subarea 1 which is in the west of “Qice Line”, subarea 2 which is between “Yangguan Line” and “Qice Line”, and subarea 3 which is between “Hu Line” and “Yangguan Line”) from 1960 to 2017, where there were significant change-points (P<0.05). Specifically, the average rainfall concentration in subarea 1 showed a significant downward trend (P<0.05). The significant change-points in rainfall concentration of the entire study area were mainly concentrated in the 1980s, 1990s, and 2010s (P<0.05). Furthermore, the maximum multi-year average rainfall concentration was distributed in subarea 2. There was also uneven rainfall distribution during the year, indicating obvious seasonal changes. Some areas were abnormally concentrated or continued to decrease, thereby flatting the distribution of rainfall over the year in the future. 2) The average rainfall concentration varied greatly in the entire study area. Specifically, the three sub-regions from 1960 to 2017 presented a main cycle of about 40 a, and a secondary cycle of about 24 a. The overall cycle changes of rainfall concentration in the entire study area and three sub-regions remained the same, indicating no obvious difference. 3) There were cold and hot spots in the spatial distribution of rainfall concentration from 1960 to 2017. The rainfall concentration in cold spots showed a significant decreasing trend (P<0.05), while continued to decrease in the future. The rainfall concentration in hotspots presented an insignificant decreasing trend (P>0.05). The interannual variation was higher than that in cold spots. 4) North Atlantic Oscillation (NAO) and Pacific Decade Oscillation Index (PDO) presented a strong influence on the changes in rainfall concentration, where different atmospheric circulation factors had different effects on rainfall concentration. At the same time, the distribution difference of landform in Northwest China has a certain impact on the change of rainfall concentration. The rainfall concentration in the high mountainous landforms is the highest, with an average of 28.55. Consequently, much more attention can be paid to the influence of abnormal factors of atmospheric circulation on rainfall concentration, especially the distribution of rainfall in arid and semi-arid regions over the year. The findings can provide scientific support to ecological and environmental protection, as well as the response to water resources in the Northwest region. [ABSTRACT FROM AUTHOR]

Dali River Basin locates in the middle reaches of the Yellow River Basin, to serve as an important support to the industry and agriculture in northern China. The change of runoff-sediment has become a key issue for the high-quality development of the Yellow River Basin. Since the 1950s, large-scale projects of water and soil conservation have been performed on the middle reaches of the Yellow River, such as Dali River, in order to improve the local ecological environment in the future. Runoff and sediment load have decreased significantly, and the relationship between water and sediment load has changed in recent years. In this study, Mann-Kendall trend test was used to analyze varying trend of runoff sediment load in the Dali River Basin from 1960 to 2015, and then the coordination degree theory and the Pettitt test method were used to clarify the change-point of the relationship between runoff and sediment load. Copula method was selected to verify the obtained change-point data via the joint cumulative probability of runoff and sediment load. The results show that: (1) the runoff and sediment load in the Dali River Basin indicated a significant downward trend at different time scales, such as monthly and annual scales. The variation in runoff and sediment load depended significantly on the external environment; (2) in the relationship between runoff and sediment load, the change-point occurred in 1996, indicating the year of 1996 was a turning point in the management of soil and water loss in the Dali River Basin; (3) after the change-point, both runoff and sediment load were significantly reduced. The reduction was higher than that before the change-point, where the reduction of sediment load was 29.19 percentage points higher than that of runoff, while the contribution of runoff to sediment load decreased by 5.10%, indicating the decrease in sediment transport of runoff per unit; (4) check dam construction and vegetation restoration can be the main factors for the changes of water and sediment load in the Dali River Basin. From 1998 to 2015, Normalized Difference Vegetation Index (NDVI) change in the Dali River Basin has shown a significant increase trend, indicating that the policy of returning farmland to forests has been effectively implemented in local regions. The restoration of vegetation has a positive effect on the reduction of runoff and sediment load. Most check dams have been built in the Dali River Basin, to directly intercept the sediment, while the triggered some changes of runoff, can indirectly prevent the generation and transportation of the sediment. The findings can provide a theoretical basis and promising potentials to clarify the change of water-sediment relationship, the control of soil erosion, and the soil and water conservation in the Dali River Basin, particularly in the Loess Plateau. [ABSTRACT FROM AUTHOR]

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Copyright of Geomatics & Information Science of Wuhan University is the property of Geomatics & Information Science of Wuhan University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To master the structure pattern and moving type of key strata is the basis of analyzing mine pressure in a fully mechanized mining face with large mining height. With the theoretical analysis applied，two structure patterns and six moving types of key strata were put forward，and the forming conditions of structure patterns and moving types were given. The two structure patterns include “cantilever” structure morphology in the caved zone and stable “hinged” structure morphology in the fractured caved zone. The six moving types include “cantilever” directly baggy fall type，“cantilever” bi-directional rotation baggy fall type，“cantilever” quadratic rotation baggy fall type，“cantilever-hinge” alternating movement type，“voussoir beam” moving type and “short voussoir beam” moving type. The six moving types of key strata in caved zone were verified by the UDEC numerical simulation method，and the different influence laws of the six moving types of key strata in caved zone on the mine pressure were revealed，which were also verified by the measured data. [ABSTRACT FROM AUTHOR]