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 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.

scholarly journals Impacts of Consolidation Time on the Critical Hydraulic Gradient of Newly Deposited Silty Seabed in the Yellow River Delta

2021 ◽  
Vol 9 (3) ◽  
pp. 270
Author(s):  
Meiyun Tang ◽  
Yonggang Jia ◽  
Shaotong Zhang ◽  
Chenxi Wang ◽  
Hanlu Liu
Keyword(s):  
Yellow River ◽  
Yellow River Delta ◽  
Hydraulic Gradient ◽  
River Delta ◽  
Theoretical Formula ◽  
The Yellow River ◽  
The Yellow River Delta ◽  
Critical Hydraulic Gradient ◽  
Seepage Flows ◽  
The Yrd

The silty seabed in the Yellow River Delta (YRD) is exposed to deposition, liquefaction, and reconsolidation repeatedly, during which seepage flows are crucial to the seabed strength. In extreme cases, seepage flows could cause seepage failure (SF) in the seabed, endangering the offshore structures. A critical condition exists for the occurrence of SF, i.e., the critical hydraulic gradient (icr). Compared with cohesionless sands, the icr of cohesive sediments is more complex, and no universal evaluation theory is available yet. The present work first improved a self-designed annular flume to avoid SF along the sidewall, then simulated the SF process of the seabed with different consolidation times in order to explore the icr of newly deposited silty seabed in the YRD. It is found that the theoretical formula for icr of cohesionless soil grossly underestimated the icr of cohesive soil. The icr range of silty seabed in the YRD was 8–16, which was significantly affected by the cohesion and was inversely proportional to the seabed fluidization degree. SF could “pump” the sediments vertically from the interior of the seabed with a contribution to sediment resuspension of up to 93.2–96.8%. The higher the consolidation degree, the smaller the contribution will be.

Variation of soil nutrients and particle size under different vegetation types in the Yellow River Delta

2014 ◽  
Vol 34 (3) ◽  
pp. 148-153 ◽  
Author(s):  
Shuying Jiao ◽  
Min Zhang ◽  
Yamei Wang ◽  
Junqing Liu ◽  
Yiongqiang Li
Keyword(s):  
Particle Size ◽  
Soil Nutrients ◽  
Yellow River ◽  
Yellow River Delta ◽  
River Delta ◽  
The Yellow River ◽  
Vegetation Types ◽  
The Yellow River Delta

scholarly journals Holocene environmental evolution history based on sporopollenin and micropaleontological reconstruction of KY-01 in the Yellow River Delta

2021 ◽  
Author(s):  
Wang Kui-Feng ◽  
Yu Xue-Feng ◽  
Xia Jiang-Bao ◽  
Xu Shu-Jian ◽  
Zhang Tai-Ping ◽  
...  
Keyword(s):  
Land Surface ◽  
Yellow River ◽  
Sedimentary Environment ◽  
Yellow River Delta ◽  
River Delta ◽  
Small Scale ◽  
The Yellow River ◽  
Carbonate Content ◽  
14C Dating ◽  
The Yellow River Delta

Abstract The Yellow River Delta adjacent to the Bohai Sea is located in the monsoon region of northern China, which is sensitive to global climate change. The core data of KY-01 borehole in the Yellow River Delta and the published records were used to reconstruct the climate environment. Based on the analysis of carbonate content, magnetic susceptibility, Ostracoda, foraminifera, sporopollenin and AMS 14C dating on the KY-01 borehole sediment core, the evolution of both the climate and sedimentary environment has been discussed. The results show that: 7656–4145 cal.aBP, seawater moved toward the land surface and the climate was generally warm and humid, when there were small-scale extreme climate fluctuations; 4145–2544 cal.aBP, transgression and recession occurred, the climate changed from warm-wet to dry-cold and there were small-scale extreme climatic events; and 2544 cal.aBP–1855 AD, the sea level was relatively low, transgression and retreat alternately occurred, the climate was drier and colder than the previous stage and the warming and cooling alternated. During the middle Holocene, cold-dry events occurred between 5737–5422 and 4451–4081 cal.aBP, which is consistent with both Chinese and worldwide climate records.

scholarly journals Accretion–Erosion Dynamics of the Yellow River Delta and the Relationships with Runoff and Sediment from 1976 to 2018

Water ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 2992
Author(s):  
He Li ◽  
Chong Huang ◽  
Qingsheng Liu ◽  
Gaohuan Liu
Keyword(s):  
Growth Rate ◽  
Yellow River ◽  
Yellow River Delta ◽  
Annual Growth ◽  
The Yellow River ◽  
Annual Growth Rate ◽  
Land Area ◽  
The Yellow River Delta ◽  
The Yrd

Timely understanding of the coastal accretion–erosion dynamics of the Yellow River Delta (YRD) can not only deepen the understanding of the evolution of the delta but also provide scientific support for water-sediment regulation (WSR) in the lower reaches of Yellow River and the implementation of a protection strategy for the Yellow River Estuary. In this long-term study, Landsat images from 1976 to 2018 were acquired, and the cloud processing platform of the Google Earth Engine was used for extraction of coastlines. On the basis of these coastlines, the area and accretion–erosion dynamics were analyzed. Then, after statistical analysis of the interannual and intra-annual variations in runoff and sediment, we discuss the relationship between the accretion–erosion dynamics and the annual runoff and sediment. The results show that (1) the coastline of the YRD lengthened first and then shortened, and the average annual growth rate was 1.48 km/a. (2) The land area of the YRD showed a significant accretionary trend before 1996, with an average annual growth rate of 28.60 km2/a. Then, the area gradually decreased from 1997 to 2001. After WSR was implemented in 2002, the accretion–erosion dynamics gradually became smooth, with an annual growth rate of 0.31 km2/a. (3) After WSR, the maximum annual sedimentation decreased by 79.70%. The average annual sediment discharge accounted for only 6.69% from November to March of the following year during the non-flood season. (4) With the continuous decrease in sediment discharge, the determination coefficient (R2) between the cumulative accretion–erosion area of the estuary and the annual sedimentation decreased from 0.98 in 1976–1996 to 0.77 after 2002. Overall, although WSR has maintained a steady increase in delta land area, it cannot change the long-term decrease in the land area of the delta. The insights gained from our study can provide some references for related coastline research, and will be useful to science community and decision makers for coastal environmental monitoring, management, protection, and sustainable development of the YRD.

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