scholarly journals Phenological Observations on Classical Prehistoric Sites in the Middle and Lower Reaches of the Yellow River Based on Landsat NDVI Time Series

2017 ◽  
Vol 9 (4) ◽  
pp. 374 ◽  
Author(s):  
Yuqing Pan ◽  
Yueping Nie ◽  
Chege Watene ◽  
Jianfeng Zhu ◽  
Fang Liu
Keyword(s):  
Time Series ◽  
Yellow River ◽  
The Yellow River ◽  
Ndvi Time Series

scholarly journals Regional estimation of daily to annual regional evapotranspiration with MODIS data in the Yellow River Delta wetland

2009 ◽  
Vol 13 (10) ◽  
pp. 1775-1787 ◽  
Author(s):  
L. Jia ◽  
G. Xi ◽  
S. Liu ◽  
C. Huang ◽  
Y. Yan ◽  
...  
Keyword(s):  
Time Series ◽  
Energy Balance ◽  
Land Surface ◽  
Yellow River ◽  
Yellow River Delta ◽  
The Yellow River ◽  
Vegetation Types ◽  
The Yellow River Delta ◽  
Regional Evapotranspiration ◽  
The Yrd

Abstract. Evapotranspiration (ET) from the wetland of the Yellow River Delta (YRD) is one of the important components in the water cycle, which represents the water consumption by the plants and evaporation from the water and the non-vegetated surfaces. Reliable estimates of the total evapotranspiration from the wetland is useful information both for understanding the hydrological process and for water management to protect this natural environment. Due to the heterogeneity of the vegetation types and canopy density and of soil water content over the wetland (specifically over the natural reserve areas), it is difficult to estimate the regional evapotranspiration extrapolating measurements or calculations usually done locally for a specific land cover type. Remote sensing can provide observations of land surface conditions with high spatial and temporal resolution and coverage. In this study, a model based on the Energy Balance method was used to calculate daily evapotranspiration (ET) using instantaneous observations of land surface reflectance and temperature from MODIS when the data were available on clouds-free days. A time series analysis algorithm was then applied to generate a time series of daily ET over a year period by filling the gaps in the observation series due to clouds. A detailed vegetation classification map was used to help identifying areas of various wetland vegetation types in the YRD wetland. Such information was also used to improve the parameterizations in the energy balance model to improve the accuracy of ET estimates. This study showed that spatial variation of ET was significant over the same vegetation class at a given time and over different vegetation types in different seasons in the YRD wetland.

scholarly journals Water Conservation Estimation Based on Time Series NDVI in the Yellow River Basin

2021 ◽  
Vol 13 (6) ◽  
pp. 1105
Author(s):  
Yangchengsi Zhang ◽  
Jiaqiang Du ◽  
Long Guo ◽  
Zhilu Sheng ◽  
Jinhua Wu ◽  
...  
Keyword(s):  
Time Series ◽  
Water Conservation ◽  
Large Scale ◽  
Yellow River ◽  
Yellow River Basin ◽  
Support Vector ◽  
The Yellow River ◽  
Grassland Ecosystem ◽  
Line Planning ◽  
The Yellow River Basin

Accurate estimation of the water conservation is of great significance for ecological red line planning. The water conservation of the Yellow River Basin has a vital influence on the development of the environment and the supply of ecological services in China. However, the existing methods used to estimate water conservation have many disadvantages, such as requiring numerous parameters, a complex calculation model, and using data that is often difficult acquire. It is often hard to provide sufficiently precise parameters and data, resulting in a large amount of calculation time and the difficulties in the study of large scale and long time series. In this study, a time series of the Normalized Difference Vegetation Index (NDVI) was applied to estimate water conservation in two aspects using the idea of wholeness and stratification, respectively. The overall fitting results can explain nearly 30% of the water conservation by partial least squares regression and nearly 50% of it by a support vector machine. However, the results of a stratified simulation showed that water conservation and the NDVI have a certain stratified heterogeneity among different ecosystem types. The optimal fitting result was achieved in a water/wetland ecosystem with the highest coefficient of determination (R2P) of 0.768 by the stratified support vector machine (SVM) model, followed by the forest and grassland ecosystem (both R2P of 0.698). The spatial mapping results showed that this method was most suitable for grassland ecosystem, followed by forest ecosystem. According to the results generated using the NDVI time series data, it is feasible to complete a spatial simulation of water conservation. This research can provide a reference for calculating regional or large-scale water conservation and in ecological red line planning.

scholarly journals Regional estimation of daily to annual evapotranspiration with MODIS data in the Yellow River Delta wetland

2009 ◽  
Vol 6 (2) ◽  
pp. 2301-2335 ◽  
Author(s):  
L. Jia ◽  
G. Xi ◽  
S. Liu ◽  
C. Huang ◽  
Y. Yan ◽  
...  
Keyword(s):  
Time Series ◽  
Energy Balance ◽  
Land Surface ◽  
Yellow River ◽  
Yellow River Delta ◽  
River Delta ◽  
The Yellow River ◽  
Vegetation Types ◽  
The Yellow River Delta ◽  
The Yrd

Abstract. Evapotranspiration (ET) from the wetland of the Yellow River Delta is one of the important components in the water cycle, which represents the water consumption by the plants and evaporation from the water and the non-vegetated surfaces. Reliable estimates of the total evapotranspiration from the wetland is useful information both for understanding the hydrological process and for water management to protect this natural environment. Due to the heterogeneity of the vegetation types and canopy density and of soil water content over the wetland (specifically over the natural reserve areas), it is difficult to estimate the regional evapotranspiration extrapolating measurements or calculations usually done locally for a specific land cover type. Remote sensing can provide observations of land surface conditions with high spatial and temporal resolution and coverage. In this study, a model based on the Energy Balance method was used to calculate daily ET using instantaneous observations of land surface reflectance and temperature from MODIS when the data were available on clouds-free days. A time series analysis algorithm is then applied to generate a time series of daily ET over a year period by filling the gaps in the observation series due to clouds. A detailed vegetation classification map is used to help identifying areas of various wetland vegetation types in the YRD wetland. Such information is also used to improve the parameterizations in the energy balance model to improve the accuracy of ET estimates. This study shows that spatial variation of ET is significant over the same vegetation class at a given time and over different vegetation types in different seasons in the YRD wetland.

Characteristics Identification of Runoff and Sediment Flux Based on Wavelet Analysis Approach in Lower Yellow River

2014 ◽  
Vol 700 ◽  
pp. 506-510
Author(s):  
Yu Zhi Shi ◽  
Ming Yuan Fan ◽  
Yu Yan Zhang ◽  
Hai Jiao Liu ◽  
Xiao Feng Yang
Keyword(s):  
Climate Change ◽  
Time Series ◽  
Wavelet Analysis ◽  
Yellow River ◽  
Sediment Flux ◽  
The Yellow River ◽  
Lower Yellow River ◽  
Multi Scale ◽  
Flood Season ◽  
Water And Sediment

Due to the influences of climate change and human activities, the water and sediment flux of the Yellow River are certainly changing. This paper selects monthly time series of runoff and sediment flux from 1950 to 2009 for study at Lijin station, in lower Yellow River. A widely used identification method, wavelet analysis, is applied for recognizing changing point and cycle of the runoff and sediment respectively in multi-scale of annual, flood season and non-flood season. The results indicate that there are two significant changing points in 1985, 2002 year, and cycle recognized results are different in multi-scale as well as with different hydrology factors.

scholarly journals Four Decades of Estuarine Wetland Changes in the Yellow River Delta Based on Landsat Observations Between 1973 and 2013

Water ◽  
2018 ◽  
Vol 10 (7) ◽  
pp. 933 ◽  
Author(s):  
Changming Zhu ◽  
Xin Zhang ◽  
Qiaohua Huang
Keyword(s):  
Time Series ◽  
Yellow River ◽  
Yellow River Delta ◽  
River Delta ◽  
Evolution Process ◽  
The Yellow River ◽  
The Yellow River Delta ◽  
The Past ◽  
Spatio Temporal

Yellow River Delta wetlands are essential for the migration of endangered birds and breeding. The wetlands, however, have been severely damaged during recent decades, partly due to the lack of wetland ecosystem protection by authorities. To have a better historical understanding of the spatio-temporal dynamics of the wetlands, this study aims to map and characterize patterns of the loss and degradation of wetlands in the Yellow River Delta using a time series of remotely sensed images (at nine points in time) based on object-based image analysis and knowledge transfer learning technology. Spatio-temporal analysis was conducted to document the long-term changes taking place in different wetlands over the four decades. The results showed that the Yellow River Delta wetlands have experienced significant changes between 1973 and 2013. The total area of wetlands has been reduced by 683.12 km2 during the overall period and the trend of loss continues. However, the rates and trends of change for the different types of wetlands were not the same. The natural wetlands showed a statistically significant decrease in area during the overall period (36.04 km2·year−1). Meanwhile, the artificial wetlands had the opposite trend and showed a statistically significant increase in area during the past four decades (18.96 km2·year−1). According to the change characteristics revealed by the time series wetland classification maps, the evolution process of the Yellow River Delta wetlands could be divided into three stages: (1) From 1973–1984, basically stable, but with little increase; (2) from 1984–1995, rapid loss; and (3) from 1995–2013, slow loss. The area of the wetlands reached a low point around 1995, and then with a little improvement, the regional wetlands entered a slow loss stage. It is believed that interference by human activities (e.g., urban construction, cropland creation, and oil exploitation) was the main reason for wetland degradation in the Yellow River Delta over the past four decades. Climate change also has long-term impacts on regional wetlands. In addition, due to the special geographical environment, the hydrological and sediment conditions and the location of the Yellow River mouth also have a significant influence on the evolution process of the wetlands.

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