Search

The Budyko framework is a simple but effective tool for watershed water balance estimation. Accurate estimation of the watershed characteristic parameter (Pw) is critical to accurate water balance simulations using the Budyko framework. However, there is no universal quantification criterion for the Pw because of the complex interactions between hydrologic, climatic, and watershed characteristic factors at global scales. Therefore, this research introduced the hydrologically similar groups principle into the Budyko framework and defined the criteria for quantifying Pw in similar environments. We classified global watersheds into six groups based on watershed attributes, including climate, soil moisture, and vegetation, and identified the controlling factors of the Pw in each hydrologically similar group. Our results show that the Pw is closely related to soil moisture (SM) and the power function gradually changes from positive to negative as soil moisture increases. The relationship between the Pw and fractional vegetation cover (FVC) can be described with different linear equations in different hydrologic similarity groups, except in the group with no strong seasonality and moist soils. Based on these relationships, a model for estimating the Pw (PwM) was established with multiple non-linear regression methods between the Pw and its controlling factors (SM and FVC). Then, we used bootstrapping and runoff reconstruction methods to verify the usability of PwM. The validation results illustrate that PwM overall presents a satisfactory performance through bootstrapping (R2 = 0.63) and runoff reconstruction (R2 = 0.89). Results show that the hydrologically similar groups method can quantify the Pw and the improved Budyko framework can aptly simulate global runoff, especially in humid watersheds. This study lays the basis for explaining the Pw in the Budyko framework and improves the applicability of the Budyko framework for estimating global runoff.

To reveal the hydrological effects on changes in land use and landscape pattern of the Wuhua River Basin (hereinafter referred to as the River Basin), this study investigated the upstream of Hezikou Hydrological Station on the Wuhua River; simulated the monthly runoff and sediment yield of the River Basin in a 25-year period (1986–2010) based on the widely used soil and water assessment tool (SWAT) model under the meteorological conditions from 1957 to 2012 and in the context of the landscape change; calculated the change rates in runoff and sediment yield throughout the year and examined the relativity between the rate of change in the runoff and sediment yield and that of land use type composition and landscape pattern using Spearman correlation coefficient. Results revealed the following results. First, the simulation accuracy of runoff and sediment yield based on the SWAT model reached the standard, so the SWAT model was applicable to mesoscale watersheds in hot and humid mountainous areas of southern China. Second, the River Basin was dominated by forest, accounting for around 75% of the whole basin area, followed by cropland, whereas the percentages of built-up land and water body are much lower. With the urbanization and agricultural expansion, a large area of deforestation occurred especially from 1995 to 2005, which potentially resulted in increases of runoff and sediment yield. Third, six typical landscape pattern indices of the River Basin were screened out through the factor analysis. The landscapes of the River Basin under the impact of human activities became fragmented as the spatial heterogeneity increased. Fourth, grassland had the largest soil erosion modulus followed by cropland and built-up land, cropland and forests contributing most to runoff and sedimentation. The changes in runoff and sediment yield mainly occurred near the watershed outlet and upstream in the southern of the river basin, runoff and sedimentation increased significantly in 2005, which are highly likely due to the heavy rain events and deforestation at the time. Fifth, the runoff was significantly affected by the area changes in the cropland and woodland, while the weaker and more insignificant relationship between the changes in landscape pattern indices and that of runoff and sediment yield were observed. Thus, we concluded that the changes in land use have higher and more significant impacts on the runoff and sediment yield in Wuhua River Basin, compared with landscape pattern indices. This work provides useful information for environmental managers to target efforts to reduce soil erosion and related environmental issues effectively. Further research is recommended to integrate climate change and human activities’ impacts on runoff generations and sediment yield processes.

Hyperspectral remote sensing provides a highly efficient, convenient, and non-destructive technical means for the quantitative study of the dust retention content (DRC) of plants. Based on the common greening plants in Guangzhou, this study used hyperspectral technology to explore the spectral characteristics of different plant leaves under dust pollution, and used the Pearson correlation method to construct the DRC estimation models of plants. The results show that the spectral characteristics of the dust-retention effect of plants are mainly concentrated in the visible and near-infrared wavelengths (350–1360 nm), which are important band intervals for the study of spectral characteristics and the inversion band selection. The first derivative of spectral reflectance is more suitable for constructing the DRC estimation model than the spectral reflectance, and CF has a good fitting effect, and the deviation between the Model estimated DRC and the measured DRC is small, and its R2 is 0.55 and the RMSE is 0.300 g/m2. Through this research, the application of hyperspectral remote sensing technology in the dust retention effect research of plants can be effectively promoted, which can help to quickly and non-destructively evaluate the DRC of plants, and provide a scientific basis for rational selection of green plant types and urban air quality monitoring, and lay a foundation for large-scale DRC estimation.

The scale research of landscape pattern is an important basis for the study of spatiotemporal evolution of landscape pattern and the scientific and reasonable allocation of landscape pattern. This paper takes the middle and upper reaches of Meijiang river as the research area. Combined with spatial grain size analysis and extent size analysis, the spatial scale effect was studied to select the optimal research scale in this research area. The results show that most of the appropriate grain size of landscape pattern indexes are in range of 90–150 m, and the optimal grain size scale is 150 m in Middle and Upper Reaches of Meijiang River Basin. At the grain size scale of 150 m, the spatial self-correlation of landscape pattern index over 50% is the highest at the extent size of 300 m, and the optimal extent size scale is 300 m in this basin. This paper determines the optimal scale of landscape pattern in the middle and upper reaches of Meijiang river basin, which is of great significance to the ecological balance and sustainable development of the basin.

The inspection procedure of Chinese high voltage power grid is mainly based on human inspection for many years. This is not only time-consuming and difficult, but the inspection results are also not objective and complete. Aiming at these problems, this paper gives a research method based on UAV-borne laser scanning. By taking the orthophotos of the power line corridor area and using the overlapping feature points of the image, the orientation elements of each photo are inversely calculated. According to the principle of aerial triangulation, the pixel matching algorithm is used to calculate the dense point cloud data of the survey area, and the power line point in the point cloud is selected to simulate the complete power line. By calculating the Euclidean distance between the power line and the power line protection area, the calculated result is compared with the power line safety specification to obtain information such as a tree barrier point or an early warning point. It can effectively identify many important defects such as wire-vegetation, wire-building, wire-crossing, etc., and greatly improve the quality and efficiency of the inspection process of existing high-voltage transmission lines.

The impacts of climate change and human activities on the surface runoff in the Wuhua River Basin (hereinafter referred to as the river basin) are explored using the Mann&ndash, Kendall trend test, wavelet analysis, and double-mass curve. In this study, all the temperature and precipitation data from two meteorological stations, namely, Wuhua and Longchuan, the measured monthly runoff data in Hezikou Hydrological Station from 1961 to 2013, and the land-cover type data in 1990 and 2013 are used. This study yields valuable results. First, over the past 53 years, the temperature in the river basin rose substantially, without obvious changes in the average annual precipitation. From 1981 to 2013, the annual runoff fluctuated and declined, and this result is essentially in agreement with the time-series characteristics of precipitation. Second, both temperature and precipitation had evidently regular changes on the 28a scale, and the annual runoff changed on the 19a scale. Third, forestland was the predominant land use type in the Wuhua river basin, followed by cultivated land. Major transitions mainly occurred in both land-use types, which were partially transformed into grassland and construction land. From 1990 to 2013, cultivated land was the most active land-use type in the transitions, and construction land was the most stable type. Finally, human activities had always been a decisive factor on the runoff reduction in the river basin, accounting for 85.8%. The runoff in the river basin suffered most heavily from human activities in the 1980s and 1990s, but thereafter, the impact of these activities diminished to a certain extent. This may be because of the implementation of water loss and soil erosion control policies.