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The natural fluctuation of hydrological regime is the key to maintaining the functionality and hydrological health of river ecosystems. Aiming at the change of hydrological regime in the Yellow River Basin caused by climate change and human activities, we selected daily runoff data from Lanzhou, Longmen and Huanyuankou stations (1956-2020), the representative hydrological stations in the Yellow River Basin and used the Mann-Kendall and Pettitt test methods to comprehensively evaluate the hydrological regime in the Yellow River Basin. The Mann-Kendall and Pettitt tests were used to quantitatively evaluate the extent of hydrological changes in the Yellow River Basin by using the eco-hydrological index range of change (IHA-RVA) method. The results show that a) the abrupt changes in runoff at Lanzhou, Longmen and Huayuankou stations occurred in 1984, 1987 and 1986 respectively, and that the average annual flow in the control basin at Longmen and Huayuankou stations showed a significant decrease. b) The variation of the minimum annual discharge in Lanzhou Station during 90 days is the highest, reaching 83%. The average discharge of Longmen Station in April is the highest, reaching -100%. The average increase (decrease) rate of discharge at Huayuankou Station has the highest variation, reaching -92%. c) The overall hydrological alterations at Lanzhou, Longmen, and Huayuankou stations are 34%, 37% and 51% respectively, which are all moderate. [ABSTRACT FROM AUTHOR]

Using the daily 2-minute average wind speed data from 1961 to 2020 in Yichang City, the climate tendency method, Mann-Kendall test method and wavelet analysis method were used to analyze the change trend, mutation, and periodic characteristics of average wind speed at different time scales, revealing the long-term wind speed variation patterns in the local area of the Three Gorges area. The results showed that the annual mean wind speed in Yichang City had increased in recent 60 years with a decreasing rate of 0. 084 m/ (s·10 a), and the four seasons mean wind speed had a slightly increasing trend with a similar climate tendency rate. The increase of average wind speed was the fastest in August and the slowest in June. The Mann-Kendall mutation test showed that the annual mean wind speed in Yichang City had a sudden change in 1971,1996 and 2013. Wavelet analysis showed that the annual mean wind speed changes periodically, and the first main period of the annual mean wind speed change was 32 years. [ABSTRACT FROM AUTHOR]

[Objective] The purposes of this study are to elucidate the long-term trends and periodic characteristics of runoff in the Dagu River Basin, and to offer the theoretical insights to guide water resource management and promote sustainable development in the Dagu River Basin. [Methods] The measured runoff data from the Nancun Hydrological Station（1956—2020） and the Zhazi Hydrological Station（1956—2016） were used to analyze the trend of annual runoff changes and abrupt change times using the Mann-Kendall test and sliding t-test. The Morlet continuous complex wavelet method was used to analyze the periodic characteristics of multi-year runoff in the basin. [Results] The annual runoff in the Dagu River Basin was generally declining, and there was a characteristic of more flow during the flood season（June—September） and less flow during the non-flood season. The peak flow usually occurred in August. The runoff of Nancun Station was abrupt in 1976, and the runoff of Zhazi station was abrupt in 1979. The runoff of the Dagu River Basin exhibited significant periodic variations at multiple time scales, with a dominant period of around 20 years, and significant oscillations before the 1980s. [Conclusion] The long-term series runoff of Dagu River Basin showed a trend of significant decline, and the basin runoff suddenly changed in the 1970s, and there were periodic changes in different time scales. In the future, the research on the mechanism of runoff change should be strengthened. [ABSTRACT FROM AUTHOR]

[Objective] The aims of this study are to explore the variation law of the long-term measured runoff and sediment load series, and to provide scientific support for the implementation of the western ecological security strategy by the country. [Methods] The linear trend estimation and moving average, Mann Kendall nonparametric test method, wavelet analysis method, were applied to analyze the measured data of annual runoff and sediment load series at Changmapu, Panjiazhuang, and Dangchengwan stations in the Shule River Basin. [Results](1) Both the annual runoff and sediment discharge of Shule River basin was increasing, however, the increasing trend of runoff was more significant than sediment discharge. The annual runoff of Changmapu, Panjiazhuang, and Dangchengwan stations had an obvious turning point in 1999, 2016 and 1982, respectively. The annual sediment discharge of Dangchengwan did not have sudden changes, and the sudden changes in the annual sediment discharge of Changmapu and Panjiazhuang all occurred in 1998.(2) The runoff and sediment discharge of the three representative stations in the Shule River basin all showed the evolution characteristics of multiple time scales. Wavelet analysis indicated periodicities of 58 years, 31 years, 14 years, 9 years and 5 years for annual runoff and periodicities of 48 years, 23 years, 14 years, 7 years and 5 years for annual sediment load in Changmapu. There were periodicities of 59 years, 32 years and 14 years for annual runoff and periodicities of 37 years, 14 years, 8 years and 5 years for annual sediment load in Panjiazhuang station. There were periodicities of 42 years and 5 years for annual runoff and periodicities of 16 years and 8 years for annual sediment load in Dangcheng station. [Conclusion] The overall trend of water and sediment in the Shule River Basin is increasing, and there is a significant periodic change. Except for the sediment transport in Dangchengwan, all other stations have sudden changes in water and sediment transport. Moreover, the sudden change in sediment transport at the same hydrological station lags behind the sudden change in runoff. [ABSTRACT FROM AUTHOR]

Based on GIMMS NDVI3g data from 1982 to 2015, by trend analysis, Mann-Kendall test and R/ S analysis, the temporal and spatial variation and future trend research of vegetation cover in the southwest karst area of China was studied. The results could provide a basis for ecology in this area. (1)In term of temporal variation of NDVI, annual and seasonal NDVI increased in fluctuant trends from 1982 to 2015. The annual and seasonal NDVI showed an overall trend of fluctuation and increase from 1982 to 2015, and the seasonal NDVI significantly increased. (2)In terms of the spatial distribution of NDVI, the vegetation cover was relatively better during the study period. The vegetation cover showed obvious spatial heterogeneity on the seasonal scale. The areas of NDVI≥0. 8 changed with the seasons in a trend of transferring from the western mountains of Hubei to Lincang of Yunnan. (3)The annual NDVI showed an increasing trend during the study period, up to 80. 31% and mainly in the vicinity of Yunnan-Guizhou Plateau. The variation of NDVI had significantly heterogeneity on the seasonal scale. The degradation of vegetation area changed along the Hengduan Mountains-Sichuan Basin, Guizhou-Hunan and Guangdong-Yunnan-Guizhou plateau. (4)In the future, the vegetation cover will show a continuous change. Vegetation area improvement will be 73. 30% on the annual and seasonal scales. [ABSTRACT FROM AUTHOR]

[Objective] The spatio-temporal distribution. abrupt change and periodic characteristics of rainfall erosivity and wind erosion climate erosivity in different regions of Shaanxi Province were studied > so as to provide scientific basis for soil erosion control and ecological construction in Shaanxi. Methods] The daily meteorological data of 96 stations in Shaanxi Province from 1981 to 2020 were used to calculate the rainfall erosivity and wind erosion climatic erosivity to analyze the change of water-wind erosion climate erosivity using methods such as climate trend analysis, spatial interpolation, Mann-kendall trend test and wavelet analysis. [Results] (1) The rainfall erosivity in Shaanxi from 1 981 to 2020 was 2 71 9.6 MJ * mm/(hm' • h). with large spatial differences, showing a spatial distribution of high in the south and low in the north. The wind erosion climatic erosivity froni 1981 to 2020 was 3.18, with a decreasing trend froni north to south. (2) Tn the past 4() years, the rainfall erosivity in Shaanxi showed an evident inter-annual variation with general upward but not passing a significant test. The rainfall erosion experienced a variation trend of first increasing and then decreasing, and it was stronger in the current era. The wind erosion climatic erosivity also showed an evident inter-annual variation, but the change trend was not significant. It experienced a variation trend of first decreasing and then increasing. Tt was strongest in the 1 990s and weakest in the current era. The rainfall erosivity was mainly larger from June to September, and the maximum value appeared in July. The wind erosion climatic erosivity was larger in winter and spring, and the maximum value was in April. The two erosivities were obviously asynchronous. (4) There were three oscillation periods of rainfall erosivity in Shaanxi Province, which was 2〜4 years, 8 years and 31 〜32 years. There were two oscillation periods of wind erosion climatic erosivity, which were 5〜1() years and 31 〜32 years. The abrupt change of rainfall erosivity occurred significantly in 2009, since then the rainfall erosivity increased gradually. Conclusion] At present, the rainfall erosivity in most areas of Shaanxi Province is strong, especially in northern Shaanxi with the strongest wind erosion climate erosivity. The wind erosion climate erosivity in eastern Yulin also showed an upward trend in recent 4() years. Therefore, more attention should be paid to the increase of wind erosion and water erosion climate erosivity in these areas. [ABSTRACT FROM AUTHOR]

In order to study the characteristics of climate change in the Yellow River Basin, temporal and spatial variation of precipitation from 1961 to 2019 in this basin were analyzed by using linear trend, moving average, Mann-Kendall test and empirical orthogonal function decomposition (EOF). From 1961 to 2019, the precipitation in the Yellow River Basin generally showed a downward trend, but the downward trend was not significant. 1961-1972 and 1985-2001 were two periods of annual precipitation decline. Annual precipitation increased from 1973 to 1984 and from 2002 to 2019. There was a sudden decrease for annual precipitation before or after 1964. The overall summer and winter precipitation of the Yellow River Basin showed an increasing trend but not statistically significant, while the spring and autumn showed no significant decreasing trend. Except for the upstream watersheds, which showed a significant increasing trend in winter, all watersheds showed no significant increasing or decreasing trend in the four seasons. According to EOF analysis, the first two eigenvectors of the annual precipitation field in the Yellow River basin from 1961 to 2019 can better express their spatial-temporal variation characteristics. The first modal eigenvector field shows consistent distribution and the second eigenvector field shows “northwest-southeast” antiphase distribution. According to its time coefficient, precipitation characteristics in different years in the Yellow River basin can be divided into four distribution forms of less in the whole basin, more in the whole basin, more in the southeast (less in the northwest) and more in the northwest (less in the southeast). [ABSTRACT FROM AUTHOR]

According to the data of precipitation and surface water resources in Henan Province from 1956 to 2016, the accumulated deviation, Mann-Kendall test, rainfall-runoff double mass curve, comparative method of cumulative slope change ratio were used to indicate the variation trend of precipitation and surface water resources and the evolution relations between them. Both precipitation and surface water resources had a decreasing trend, while the decreasing trend was more significant in surface water resources. Surface water resources in the Haihe River and the Yellow River Basin decreased more significant than that in the Huaihe River and the Yangtze River Basin. Since the 1990 s, rainfall-runoff relationship had changed in some hydrological stations of the Haihe River and the Yellow River Basin. Taking Xincun hydrological station as an example, quantified the influence of precipitation and human activities on runoff. The results show that precipitation has little influence on runoff while human activities is the main factor of runoff variation. [ABSTRACT FROM AUTHOR]

The study on the temporal and spatial variation and probability characteristics of extreme precipitation can provide theoretical basis for the prevention and control of mountain flood disaster in the study area and flood control and drainage in cities and towns, and is of great significance to people’s production and life as well as the sustainable development of social economy. Based on the Shaanxi Meteorological Information Center offered the Guanzhong area in the province of 36 representative meteorological offices and stations from 1965 to 2014, a total of 50 years of daily observed precipitation data as the foundation, the year the maximum sampling method（AM), super value sampling method（AE) and super threshold peak sampling method（POT) for data sampling, through the Mann-Kendall test of extreme precipitation in the area of trend analysis, and the linear moment method, K-S test on its probability characteristics were studied. The results show that a) according to the average extreme precipitation in Guanzhong area, the distribution of precipitation is smaller in the middle and larger in the four weeks; b) the annual extreme precipitation in the west and east of Guanzhong shows a decreasing trend, while in contrast, the annual extreme precipitation in the central region, the northeast region and the southwest region shows an increasing trend; c) the distribution of P-Ⅲ universality and fitting precision is superior to GEV and GP distribution, more suitable to describe the Shaanxi Guanzhong region in extreme precipitation probability distribution and; d) the overall fitting accuracy of AM sequence is significantly better than that of AE and POT sequence. [ABSTRACT FROM AUTHOR]

In order to grasp the climate change law of extreme precipitation in Shenzhen, based on the daily precipitation data of Shenzhen from 1961 to 2019, 11 extreme precipitation indexes and coefficients of variation were calculated, and abnormal values of annual precipitation were detected. Linear trend method and Mann-Kendall were used. Catastrophe analysis and other methods analyzed the changes of extreme precipitation and abnormal precipitation in Shenzhen. The results show that in the past 59 years, Shenzhen's extreme precipitation index has significant fluctuation characteristics; the daily precipitation thresholds for determining heavy and extremely heavy precipitation are 59.7 mm and 130.4 mm, respectively, which roughly correspond to the level of heavy rain and heavy rain; extreme precipitation changes are mainly manifested as follows: The number of moderately rainy days (R 10) increased significantly; the maximum 1-day precipitation (R x1day), the maximum 5-day precipitation (R x5day ), and the number of moderate rain days (R 10), three extreme precipitation indices, all changed abruptly around 1980 1963 was a typical year with abnormally low precipitation, and 2001 and 2008 were typical years with abnormally high precipitation. In the past 30 years, the frequency of abnormal annual precipitation has increased significantly, twice as much as the previous 29 years. The above results all indicate that Shenzhen faces a high risk of urban waterlogging disasters in the future. [ABSTRACT FROM AUTHOR]