scholarly journals Spatio-temporal changes in evapotranspiration over China using GLEAM_V3.0a products (1980–2014)

2018 ◽  
Vol 49 (5) ◽  
pp. 1330-1348 ◽  
Author(s):  
Xiuqin Yang ◽  
Bin Yong ◽  
Yixing Yin ◽  
Yuqing Zhang
Keyword(s):  
River Basin ◽  
Spatial Patterns ◽  
Seasonal Variations ◽  
Annual Variation ◽  
Southern China ◽  
Global Land ◽  
Southwest Region ◽  
The Mean ◽  
Spatio Temporal ◽  
The Impact

Abstract This study used land evapotranspiration (ET) values from 61 ChinaFLUX eddy covariance (EC) sites and water-balanced derived ET in ten basins to investigate the performance of Global Land Evaporation Amsterdam Model (GLEAM) V3.0a ET estimates (i.e., ETG) over China. We quantified the spatio-temporal characteristics of ETG and the impact of precipitation (P) and potential ET (ETP) on ETG. ETG was appropriate for estimating daily, seasonal, and annual ET rates. The mean annual ETG increased progressively from the northwest to southeast of China. Domain-averaged annual ETG over China was 421.90 mm year−1 during 1980 to 2014. The spatial patterns of ETG were in accordance with those of annual precipitation. Low ETG values occurred in the Northwest River Basin, and relatively high ET values were found across southern China. ETG showed the highest annual variation in the Northwest River Basin and low variation in the southwest region, which captured seasonal variations with maxima in summer and minima in winter. The inter-annual variation of annual ETG and ETP differed significantly from 1980 to 2014, yielding prominent spatial variability around −16.50 to 9.10 mm year−2 and −1.90 to 4.70 mm year−2, respectively. Annual ETG is correlated well with P and ETP at each site.

scholarly journals Spatial and temporal variations of CO<sub>2</sub> mole fractions observed at Beijing, Xianghe and Xinglong in North China

2021 ◽  
Author(s):  
Yang Yang ◽  
Minqiang Zhou ◽  
Ting Wang ◽  
Bo Yao ◽  
Pengfei Han ◽  
...  
Keyword(s):  
Seasonal Variations ◽  
Human Activities ◽  
North China ◽  
Terrestrial Ecosystem ◽  
Temporal Variations ◽  
Spatial And Temporal Variations ◽  
Boundary Layer Height ◽  
The Mean ◽  
The Impact ◽  
First Time

Abstract. Atmospheric CO2 mole fractions are observed at Beijing (BJ), Xianghe (XH), and Xinglong (XL) in North China using the Picarro G2301 Cavity Ring-Down Spectroscopy instruments. The measurement system is described comprehensively for the first time. The geo-distances among these three sites are within 200 km, but they have very different surrounding environments: BJ is inside the megacity; XH is in the suburban area; XL is in the countryside on a mountain. The mean and standard deviation of CO2 mole fractions at BJ, XH, and XL between October 2018 and September 2019 are 448.4 ± 12.8 ppm, 436.0 ± 9.2 ppm and 420.6 ± 8.2 ppm, respectively. The seasonal variations of CO2 at these three sites are similar, with a maximum in winter and a minimum in summer, which is dominated by the terrestrial ecosystem. However, the seasonal variations of CO2 at BJ and XH are more affected by human activities as compared to XL. By using CO2 at XL as the background, CO2 enhancements are observed simultaneously at BJ and XH. The diurnal variations of CO2 are driven by the boundary layer height, photosynthesis and human activities at BJ, XH and XL. Moreover, we address the impact of the wind on the CO2 mole fractions at BJ and XL. This study provides an insight into the spatial and temporal variations of CO2 mole fractions in North China.

scholarly journals Continuous Monitoring of the Spatio-Temporal Patterns of Surface Water in Response to Land Use and Land Cover Types in a Mediterranean Lagoon Complex

2019 ◽  
Vol 11 (12) ◽  
pp. 1425 ◽  
Author(s):  
Zhichao Li ◽  
Yujie Feng ◽  
Nadine Dessay ◽  
Eric Delaitre ◽  
Helen Gurgel ◽  
...  
Keyword(s):  
Surface Water ◽  
Human Activities ◽  
Coastal Wetlands ◽  
Annual Variation ◽  
Coastal Lagoons ◽  
Sand Beach ◽  
Mediterranean Lagoon ◽  
Potential Link ◽  
Spatio Temporal ◽  
The Impact

Mediterranean coastal lagoons and their peripheral areas often provide a collection of habitats for many species, and they often face significant threats from anthropogenic activities. Diverse human activities in such areas directly affect the spatio-temporal dynamic of surface water and its ecological characteristics. Monitoring the surface water dynamic, and understanding the impact of human activities are of great significance for coastal lagoon conservation. The Regional Natural Park of Narbonne includes a typical Mediterranean lagoon complex where surface water dynamic and its potential link with local diverse human activities has not yet been studied. In this context, based on all the available Landsat images covering the study area during 2002–2016, this study identified the water and non-water classes for each satellite observation by comparing three widely used spectral indices (i.e., NDVI, NDWI and MNDWI) and using the Otsu method. The yearly water frequency index was then computed to present the spatio-temporal dynamic of surface water for each year, and three water dynamic scenarios were also identified for each year: permanent water (PW), non-permanent water (NPW) and non-water (NW). The spatial and inter-annual variation in the patterns of the three water scenarios were characterized by computing the landscape metrics at scenario-level quantifying area/edge, shape, aggregation and fragmentation. Finally, the quantitative link between different land use and land cover (LULC) types derived from the LULC maps of 2003, 2012 and 2015 and the surface water dynamic scenarios was established in each of the 300 m × 300 m grid cells covering the study area to determine the potential impact of human activities on the surface water dynamic. In terms of the inter-annual variation during 2002–2016, PW presented an overall stability, and NPW occupied only a small part of the water surface in each year and presented an inter-annual fluctuation. NPW had a smaller patch size, with lower connectivity degree and higher fragmentation degree. In terms of spatial variation during 2002–2016, NPW often occurred around PW, and its configurational features varied from place to place. Moreover, PW mostly corresponded to the natural lagoon, and salt marsh (as a part of lagoons), and NPW had a strong link with arable land (agricultural irrigation) and salt marsh (salt production), sand beach/dune, coastal wetlands and lagoon for the LULC maps of 2003, 2012 and 2015. However, more in-depth analysis is required for understanding the impact of sand beach/dune, coastal wetlands and lagoon on surface water dynamics. This study covers the long-term variations of surface water patterns in a Mediterranean lagoon complex having intense and diverse human activities, and the potential link between LULC types and the water dynamic scenarios was investigated on different dates. The results of the study should be useful for environmental management and protection of coastal lagoons.

scholarly journals The Current and Future Potential Geographical Distribution and Evolution Process of Catalpa bungei in China

Forests ◽  
2022 ◽  
Vol 13 (1) ◽  
pp. 96
Author(s):  
Shengqi Jian ◽  
Tiansheng Zhu ◽  
Jiayi Wang ◽  
Denghua Yan
Keyword(s):  
Climate Change ◽  
River Basin ◽  
Shaanxi Province ◽  
Ecological Management ◽  
Multiple Model ◽  
The North ◽  
Mean Temperature ◽  
Catalpa Bungei ◽  
The Mean ◽  
The Impact

Catalpa bungei C. A. Mey. (C. bungei) is one of the recommended native species for ecological management in China. It is a fast-growing tree of high economic and ecological importance, but its rare resources, caused by anthropogenic destruction and local climatic degradation, have not satisfied the requirements. It has been widely recommended for large-scale afforestation of ecological management and gradually increasing in recent years, but the impact mechanism of climate change on its growth has not been studied yet. Studying the response of species to climate change is an important part of national afforestation planning. Based on combinations of climate, topography, soil variables, and the multiple model ensemble (MME) of CMIP6, this study explored the relationship between C. bungei and climate change, then constructed Maxent to predict its potential distribution under SSP126 and SSP585 and analyzed its dominant environmental factors. The results showed that C. bungei is widely distributed in Henan, Hebei, Hubei, Anhui, Jiangsu, and Shaanxi provinces and others where it covers an area of 2.96 × 106 km2. Under SSP126 and SSP585, its overall habitat area will increase by more than 14.2% in 2080–2100, which mainly indicates the transformation of unsuitable areas into low suitable areas. The center of its distribution will migrate to the north with a longer distance under SSP585 than that under SSP126, and it will transfer from the junction of Shaanxi and Hubei province to the north of Shaanxi province under SSP585 by 2100. In that case, C. bungei shows a large-area degradation trend in the south of the Yangtze River Basin but better suitability in the north of the Yellow River Basin, such as the Northeast Plain, the Tianshan Mountains, the Loess Plateau, and others. Temperature factors have the greatest impact on the distribution of C. bungei. It is mainly affected by the mean temperature of the coldest quarter, followed by precipitation of the wettest month, mean diurnal range, and precipitation of the coldest quarter. Our results hence demonstrate that the increase of the mean temperature of the coldest quarter becomes the main reason for its degradation, which simultaneously means a larger habitat boundary in Northeast China. The findings provide scientific evidence for the ecological restoration and sustainable development of C. bungei in China.

scholarly journals Relative Importance of Land Use and Climate Change on Hydrology in Agricultural Watershed of Southern China

2020 ◽  
Vol 12 (16) ◽  
pp. 6423
Author(s):  
Lanhua Luo ◽  
Qing Zhou ◽  
Hong S. He ◽  
Liangxia Duan ◽  
Gaoling Zhang ◽  
...  
Keyword(s):  
Climate Change ◽  
Land Use ◽  
Land Use Change ◽  
River Basin ◽  
Laboratory Experiments ◽  
Southern China ◽  
Swat Model ◽  
Efficiency Coefficient ◽  
Soil Database ◽  
The Impact

Quantitative assessment of the impact of land use and climate change on hydrological processes is of great importance to water resources planning and management. The main objective of this study was to quantitatively assess the response of runoff to land use and climate change in the Zhengshui River Basin of Southern China, a heavily used agricultural basin. The Soil and Water Assessment Tool (SWAT) was used to simulate the river runoff for the Zhengshui River Basin. Specifically, a soil database was constructed based on field work and laboratory experiments as input data for the SWAT model. Following SWAT calibration, simulated results were compared with observed runoff data for the period 2006 to 2013. The Nash-Sutcliffe Efficiency Coefficient (NSE) and the correlation coefficient (R2) for the comparisons were greater than 0.80, indicating close agreement. The calibrated models were applied to simulate monthly runoff in 1990 and 2010 for four scenarios with different land use and climate conditions. Climate change played a dominant role affecting runoff of this basin, with climate change decreasing simulated runoff by −100.22% in 2010 compared to that of 1990, land use change increasing runoff in this basin by 0.20% and the combination of climate change and land use change decreasing runoff by 60.8m3/s. The decrease of forestland area and the corresponding increase of developed land and cultivated land area led to the small increase in runoff associated with land use change. The influence of precipitation on runoff was greater than temperature. The soil database used to model runoff with the SWAT model for the basin was constructed using a combination of field investigation and laboratory experiments, and simulations of runoff based on that new soil database more closely matched observations of runoff than simulations based on the generic Harmonized World Soil Database (HWSD). This study may provide an important reference to guide management decisions for this and similar watersheds.

Quantifying the impacts of anthropogenic activity on chemical weathering based on source identification of hydrochemistry: the Liuxi river basin, southern China

2020 ◽  
Vol 22 (12) ◽  
pp. 2406-2417
Author(s):  
Zhigang Yang ◽  
Zuobing Liang ◽  
Lei Gao ◽  
Rui Li ◽  
Zhuowei Wang ◽  
...  
Keyword(s):  
River Basin ◽  
Source Identification ◽  
Chemical Weathering ◽  
Southern China ◽  
Anthropogenic Activity ◽  
The Impact

The impact of anthropogenic activity on chemical weathering is still an open and significant topic that requires clarification to improve the understanding of watershed evolution.

Assessing the impact of climate and land-use change on the hydrological response of the upper Betwa River basin

2021 ◽  
Author(s):  
Amit Kumar ◽  
Kumar Gaurav
Keyword(s):  
Land Use ◽  
Land Use Change ◽  
River Basin ◽  
Assessment Tool ◽  
Hydrological Cycle ◽  
Central India ◽  
Hydrological Response ◽  
Open Land ◽  
The Mean ◽  
The Impact

&lt;p&gt;Climate and land-use change have altered the regional hydrological cycle. As a result, the mean summer monsoon rainfall has decreased by 10 % over central India during 1950-2015. This study evaluates the combined effect of climate and land-use change on the hydrological response of the upper Betwa River basin in Central India. We use Landsat satellite images from 1990 to 2018 to compute the changes in various land-use types; waterbody, built-up, forest, agriculture, and open land. In the past two decades, we found that the water body, built-up, and cropland have increased by 63 %, 65 %, and 3 %, respectively. However, forest and open land have decreased by 16 % and 23 %. Further, we observed a significant increase in annual average temperature and a decrease in the mean rainfall in the study area during 1980-2018.&lt;/p&gt;&lt;p&gt;We then coupled the land-use change with weather parameters (precipitation, temperature, wind speed, solar radiation, and relative humidity) and setup the SWAT (Soil and water assessment tool) model to simulate the hydrological responses in the catchment. We have run this model for two different time steps, 1980-2000 and 1998-2018, using the land-use of 1990 and 2018. Calibration and validation are performed for (1991-1994, 2000-2004) and (1995-1998, 2005-2008) respectively using SUFI-2 method. Our results show that the surface runoff and percolation decreased by -21 and -9 %, whereas evapotranspiration increased by 3 % in the upper Betwa River basin during 2001-2018. A decrease in rainfall, runoff, and percolation will have considerable implications on regional water security.&lt;/p&gt;

scholarly journals Spatio-temporal Analysis of Anthropogenic Disturbances on Landscape Pattern of Tourist Destinations: a case study in the Li River Basin, China

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Yunyun Xiang ◽  
Jijun Meng ◽  
Nanshan You ◽  
Peixiong Chen ◽  
Hui Yang
Keyword(s):  
River Basin ◽  
Spatial Differentiation ◽  
Temporal Analysis ◽  
Anthropogenic Disturbances ◽  
Landscape Patterns ◽  
Recreation Ecology ◽  
Tourist Destinations ◽  
Spatio Temporal ◽  
Disturbance Model ◽  
The Impact

AbstractThe impact of human-related activities on the eco-environment of tourist destinations is an important part of recreation ecology research. However, traditional studies have mainly concentrated on the static influences upon the simple factors of soil or vegetation in tourist destinations, and the relationship between anthropogenic disturbances and landscape patterns is little understood. In this study, we constructed a disturbance model on a landscape scale to identify and quantify the main anthropogenic disturbances. The overall variation coefficient (OVC) index is defined as the intensity of different disturbance sources, and landscape structure analysis methods are used for temporal and spatial differentiation, which is applied in the Li River Basin, China. Three typical types of human-related activities are identified as possible anthropogenic disturbance sources in the region, and their notable influential spheres are determined. Then, the dynamic changes in tourism disturbance in two periods and the spatial distribution characteristics related to three factors are explored. The results suggest that settlement and tourism disturbances have exerted considerable impacts on landscape patterns, and the differentiation characteristics are closely related to local tourism development policies and patterns. The disturbance model could be applied in other tourism destinations and provide countermeasures for regional tourism management.

scholarly journals NEOTECTONIC SIGNIFICANCE REVEALED BY STREAM LENGTH &#8211; GRADIENT INDEX OF THE DAXI RIVER BASIN IN THE SOUTHERN MARGIN OF ORDOS, CHINA

2020 ◽  
Vol XLII-3/W10 ◽  
pp. 967-973
Author(s):  
L. Han ◽  
C. Y. Du ◽  
Z. H. Liu
Keyword(s):  
River Basin ◽  
The Tibetan Plateau ◽  
Eurasian Plate ◽  
Power Functions ◽  
Stream Length ◽  
Southern Margin ◽  
Cenozoic Era ◽  
The Mean ◽  
The Impact ◽  
Auxiliary Role

Abstract. Since the late Cenozoic era, due to the impact of the Indo- Eurasian plate collision and the northeasterward compression of the Tibetan Plateau, a series of extensional sub-basins and tectonic belts have been formed at the periphery of the Ordos block. Watershed geomorphology plays an important role in studying the formation of rock uplift and river erosion, and are recording the surface evidence on landforms evolution. In this paper, twenty-eight sub-basins and tributaries around Daxihe River, locating at the southern margin of Ordos, were extracted from SRTM1 DEM data. Combined with Hack profile and related river parameters, the tectonic and geomorphic morphology were evaluated synthetically. The results show that (1) The mean SL of this area is 93.9, indicating that the tectonic activities are strong in Daxihe River Basin; (2) The SL values of the northern and southern are 58.9–152 and 66–137.4, respectively, showing that the uplift rate of eastern margin larger than the southern margin; (3) There are positive power functions between K and drainage area, also between landform relief and slope. This study plays an auxiliary role in regional geological background, structural activity analysis and disaster prediction.

scholarly journals Variations in runoff, sediment load and their relationship for a major sediment source area of the Jialing River basin, southern China

2020 ◽  
Author(s):  
Yiting Shao ◽  
Xingmin Mu ◽  
Yi He ◽  
Kai Chen
Keyword(s):  
River Basin ◽  
Sediment Load ◽  
Southern China ◽  
Annual Runoff ◽  
Jialing River ◽  
Change Period ◽  
Runoff Sediment ◽  
Monthly Runoff ◽  
The Impact ◽  
The Relationship

Investigation of the variations in runoff and sediment load as well as their dynamic relation is conducive to understanding hydrological regimes changes and supporting channel regulation and fluvial management. This study was undertaken in the Xihanshui catchment, which is known for its high sediment-laden in the Jialing River of the Yangtze River basin, southern China, to evaluate the change characteristics of runoff, sediment load and their relationship at multi-temporal scales from 1966 to 2016. The results showed that the monthly runoff changed significantly for more months whereas the significant changes in monthly sediment load occurred from April to September. The contributions of runoff in summer and autumn and sediment load in summer to their annual value changes were greater. The annual runoff and sediment load in the Xihanshui catchment both exhibited significant decreasing trends (P<0.05) with significant mutation in 1993 (P<0.05). The average annual runoff in the change period (1994-2016) decreased by 49.60% and annual sediment load displayed a substantial decline with a reduction of 77.76% in comparison with the reference period (1966-1993). The variation of the relationship between runoff and sediment load in the catchment was time-dependent. The annual and extreme monthly runoff-sediment relationship could be generally expressed as power function, whereas the monthly runoff-sediment relationships were changeable. Spatially, the relationship between annual runoff and sediment load could be partly attributed to sediment load changes in the upstream and runoff variations in the downstream and it became weaker in the change period due to the impact of existing soil and water conservation measures. Quantitative assessment showed that human activity played a dominant role in annual runoff and sediment load reduction, with the contributions of 67.07% and 87.64%, respectively.

scholarly journals Monthly and seasonal rainfall (1963–2017) for a typhoon-influenced area in a Chinese karst basin

2018 ◽  
Author(s):  
Chongxun Mo ◽  
Yuli Ruan ◽  
Jiaqi He ◽  
Guikai Sun ◽  
Juliang Jin
Keyword(s):  
River Basin ◽  
Annual Variation ◽  
Abrupt Change ◽  
Seasonal Rainfall ◽  
Rain Gauges ◽  
Average Rainfall ◽  
Annual Distribution ◽  
Autumn And Winter ◽  
The Impact ◽  
Main Factor

Abstract. Under the dual influence of global warming and typhoon weather, the characteristics of monthly and seasonal rainfall become more complicated and extreme, leading to more frequent rainfall and flood disasters. The objective of this study is to propose a framework for analysing the characteristics of rainfall and its correlation with typhoons. The proposed framework consists of an analysis of inner-annual distribution, inter-annual variation as well as correlation between rainfall and typhoons. Especially, a DVM method is proposed to compute the rationality and reliability of the abrupt change time analysis. Finally, the proposed framework was successfully implemented using a 55-year time series (1963–2017) of rainfall data recorded by 12 rain gauges in Chengbi River Basin (South China).The results are as follows. (1) The relative variability of monthly rainfall is relatively large (above 30 %), and the rainfall tends to be centralized, and is mainly concentrated in July. (2) The monthly average rainfall is relatively stable, the seasonal rainfall decreases in spring and summer, while increases in autumn and winter. The abrupt change occurred during 1980s–1990s.The main periods of rainfall in summer and winter are shorter than those in spring and autumn. (3) The typhoon-caused rain is the main factor affecting the summer and autumn rainfall while the number of typhoons has the least influence. It is suggested that the impact of typhoon should be taken into consideration in the modelling of spatial and temporal evolution of hazardous rainfall evens and their social hazard assessment for a typhoon-influenced area .Besides, preventive measures should be strengthened for flood and waterlogging disasters and that the reservoir should be operated at different FLWLs during different flood sub seasons in Chengbi River Basin.

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