Effects of multi-time scales drought on vegetation dynamics in Qaidam River Basin, Qinghai-Tibet Plateau from 1998 to 2015

2020 ◽  
Vol 141 (1-2) ◽  
pp. 117-131 ◽  
Author(s):  
Yongxiu Sun ◽  
Shiliang Liu ◽  
Yuhong Dong ◽  
Shikui Dong ◽  
Fangning Shi
Keyword(s):  
River Basin ◽  
Time Scales ◽  
Vegetation Dynamics ◽  
Tibet Plateau ◽  
Qinghai Tibet Plateau

Effects of multi-time scales drought on vegetation dynamics in Qaidam River Basin, Qinghai-Tibet Plateau from 1998 to 2015

2020 ◽  
Author(s):  
Yongxiu Sun ◽  
Shiliang Liu ◽  
Yuhong Dong ◽  
Shikui Dong ◽  
Fangning Shi
Keyword(s):  
River Basin ◽  
Time Scales ◽  
Vegetation Dynamics ◽  
Vegetation Index ◽  
Normalized Difference Vegetation Index ◽  
Terrestrial Ecosystems ◽  
Tibet Plateau ◽  
Desert Grassland ◽  
Qinghai Tibet Plateau ◽  
Different Time Scales

<p>Quantifying drought variations at multi-time scales is important to assess the potential impacts of climate change on terrestrial ecosystems, especially vulnerable desert grassland. Based on the Normalized Difference Vegetation Index (NDVI) and Standardized Precipitation Evapotranspiration Index (SPEI), we assessed the influences of different time-scales drought (SPEI-3, SPEI-6, SPEI-12, SPEI-24, and SPEI-48 with 3, 6, 12, 24 and 48 months, respectively) on vegetation dynamics in the Qaidam River Basin, Qinghai-Tibet Plateau. Results showed that: (1) Temporally, annual and summer NDVI increased, while spring and autumn NDVI decreased from 1998 to 2015. Annual, spring and summer SPEI increased and autumn SPEI decreased. (2) Spatially, annual, spring, summer, and autumn NDVI increased in the periphery of the Basin, with 45.98%, 22.68%, 43.90%  and 30.80% of the study area, respectively. SPEI showed a reverse variation pattern with NDVI, with an obvious decreasing trend from southeast to northwest. (3) Annual vegetation growth in most areas (69.53%, 77.33%, 86.36%, 90.19% and 85.44%) was correlated with drought at all time-scales during 1998-2015. However, high spatial and seasonal differences occurred among different time-scales, with the maximum influence in summer under SPEI24. (4) From month to annual scales, NDVI of all land cover types showed higher correlation to long-term drought of SPEI24 or SPEI48. Vegetation condition index (VCI) and SPEI were positively correlated at all time-scales and had a more obvious response in summer. The highest correlation was VCI of grassland (June-July) or forest (April-May, August-October) and SPEI48. This study contributes to exploring the effect of drought on vegetation dynamics at different time scales, further providing credible guidance for regional water resources management.</p>

scholarly journals Classification of Stable Isotopes and Identification of Water Replenishment in the Naqu River Basin, Qinghai-Tibet Plateau

Water ◽  
2018 ◽  
Vol 11 (1) ◽  
pp. 46 ◽  
Author(s):  
Xi Chen ◽  
Guoli Wang ◽  
Fuqiang Wang
Keyword(s):  
Stable Isotopes ◽  
River Basin ◽  
Source Identification ◽  
Evaluation Model ◽  
Tibet Plateau ◽  
High Status ◽  
Fuzzy Evaluation ◽  
Isotopic Study ◽  
Qinghai Tibet Plateau

The stable isotopic study of the mechanism of runoff replenishment in the Qinghai-Tibet Plateau is a time-consuming and complicated process requiring complex monitoring data and scientific evaluation methods. Based on the data of water stable isotopes (18O and 2H) in the Naqu River basin, the present paper developed a framework of the variable fuzzy evaluation model (VFEM) to provide a method to classify stable isotopes and generalize the source identification of water replenishment by rainfall or snowmelt in the Naqu River basin. The grade eigenvalues of tributaries were ranked from low to high as follows: 1, 1.005, 1.089, 1.151, 1.264, 1.455 and 2.624. Three sets of tributaries were distinguished. The grade eigenvalues of the Najinqu, Bazongqu, Mumuqu, Chengqu and Gongqu Rivers were small, indicating that these tributaries were strongly supplemented by precipitation and snowmelt; the grade eigenvalue of the Zongqingqu River was in the medium range (1.455); the third group included the Mugequ River with a high status value (2.624). This study mainly highlighted the combination of the classification of stable isotopes and plots of δ2H vs. δ18O in the source identification of water replenishment, which will be helpful for studying runoff replenishment and the evolution mechanism in the Qinghai-Tibet Plateau.

Characteristics in the Spatiotemporal Variation and Periodic Evolution of Groundwater in the Xining Area of China, Eastern Qinghai–Tibet Plateau

2021 ◽  
Author(s):  
Huanhuan Li ◽  
Runze Zhan ◽  
Yudong Lu ◽  
Bao Zhou ◽  
Jing Wu
Keyword(s):  
Information System ◽  
Geographic Information System ◽  
Time Scales ◽  
Groundwater Level ◽  
Groundwater Resources ◽  
Periodic Variation ◽  
Morlet Wavelet ◽  
Groundwater Depth ◽  
Tibet Plateau ◽  
Qinghai Tibet Plateau

Abstract Groundwater, an important source of water, has profound effects on global human survival and production. The spatiotemporal characteristics of groundwater and the periodic variation law of different time scales must be analyzed to grasp the dynamic situation of groundwater and provide scientific guidance for the rational utilization and management of groundwater resources. In this study, the temporal and spatial variability and periodicity of groundwater level were studied in the Xining region of the eastern Qinghai–Tibet Plateau China using traditional statistical method, geographic information system and Morlet wavelet analysis. Results show that the groundwater dynamics in the study area are mainly controlled by three factors, namely, the amount of river water infiltration, discharge from the groundwater, and artificial exploitation. The aforementioned factors can be divided into three dynamic types according to their combination relationship: hydrological, hydrological exploitation, and runoff-discharge types. The groundwater depth showed a trend of first increasing, then stabilizing, and finally decreasing from 1980 to 2020. The analysis in spatial variability demonstrated that the groundwater depth in different periods has a great spatial difference, with a moderate spatial variation intensity. Moreover, the spatial correlation of groundwater in the abundant season is lower than that in the dry season, which is mainly caused by the strengthening of artificial exploitation. The groundwater depth in the Xining region presents a pattern of deep in the south and east and shallow in the north and west by Kriging interpolation of spherical model in geographic information system. Meanwhile, the inter-annual groundwater has continued to decline since the chronic overexploitation between the 1960s and 2000s, with a maximum cumulative depth of 15 m. Then, the amount extraction had been further reduced, and rainfall had significantly increased in recent years. Accordingly, the cone of depression has undergone an evolutionary process from an expansion period to a stable period to a shrinking period. Furthermore, the annual groundwater level of most monitoring wells in study area has the same multi-year scale time variation characteristics with an evident regular periodic variation on the 9-14a and 17-25a time scales by using Morlet wavelet transform analysis. The temporal sequence of groundwater from 1980 to 2020 has the first and second main periods of 12a and 21a. In accordance with the two time-scales, the groundwater level will continue to rise in the short term in the future, which provides a scientific theoretical basis for the long-term sustainable development of groundwater resources and government decision-making.

Characteristics of Variation in Runoff Across the Nyangqu River Basin in the Qinghai-Tibet Plateau

2012 ◽  
Vol 3 (1) ◽  
pp. 80-86 ◽  
Author(s):  
Yang Dingding ◽  
Zhou Caiping ◽  
Ouyang Hua ◽  
Chen Chuanyou
Keyword(s):  
River Basin ◽  
Tibet Plateau ◽  
Qinghai Tibet Plateau

Soil quality evaluation of the alluvial fan in the Lhasa River Basin, Qinghai-Tibet Plateau

CATENA ◽  
2022 ◽  
Vol 209 ◽  
pp. 105829
Author(s):  
Tongde Chen ◽  
Juying Jiao ◽  
Ziqi Zhang ◽  
Hong Lin ◽  
Chunjing Zhao ◽  
...  
Keyword(s):  
Soil Quality ◽  
River Basin ◽  
Quality Evaluation ◽  
Alluvial Fan ◽  
Tibet Plateau ◽  
Lhasa River Basin ◽  
Lhasa River ◽  
Qinghai Tibet Plateau
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