Correlation between hydrological drought, climatic factors, reservoir operation, and vegetation cover in the Xijiang Basin, South China

Abstract. Hydrological droughts are one of the most damaging disasters in terms of economic loss in central Vietnam and other regions of South-east Asia, severely affecting agricultural production and drinking water supply. Their increasing frequency and severity can be attributed to extended dry spells and increasing water abstractions for e.g. irrigation and hydropower development to meet the demand of dynamic socioeconomic development. Based on hydro-climatic data for the period from 1980 to 2013 and reservoir operation data, the impacts of recent hydropower development and other alterations of the hydrological network on downstream streamflow and drought risk were assessed for a mesoscale basin of steep topography in central Vietnam, the Vu Gia Thu Bon (VGTB) River basin. The Just Another Modelling System (JAMS)/J2000 was calibrated for the VGTB River basin to simulate reservoir inflow and the naturalized discharge time series for the downstream gauging stations. The HEC-ResSim reservoir operation model simulated reservoir outflow from eight major hydropower stations as well as the reconstructed streamflow for the main river branches Vu Gia and Thu Bon. Drought duration, severity, and frequency were analysed for different timescales for the naturalized and reconstructed streamflow by applying the daily varying threshold method. Efficiency statistics for both models show good results. A strong impact of reservoir operation on downstream discharge at the daily, monthly, seasonal, and annual scales was detected for four discharge stations relevant for downstream water allocation. We found a stronger hydrological drought risk for the Vu Gia river supplying water to the city of Da Nang and large irrigation systems especially in the dry season. We conclude that the calibrated model set-up provides a valuable tool to quantify the different origins of drought to support cross-sectorial water management and planning in a suitable way to be transferred to similar river basins.

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A Two-Year Study on Mercury Fluxes from the Soil under Different Vegetation Cover in a Subtropical Region, South China

Atmosphere ◽

10.3390/atmos9010030 ◽

2018 ◽

Vol 9 (1) ◽

pp. 30 ◽

Cited By ~ 5

Author(s):

Ming Ma ◽

Tao Sun ◽

Hongxia Du ◽

Dingyong Wang

Keyword(s):

South China ◽

Vegetation Cover ◽

Subtropical Region ◽

Mercury Fluxes

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Recent greening of grasslands in northern China driven by increasing precipitation

Journal of Plant Ecology ◽

10.1093/jpe/rtab036 ◽

2021 ◽

Author(s):

Kai Di ◽

Zhongmin Hu ◽

Mei Wang ◽

Ruochen Cao ◽

Minqi Liang ◽

...

Keyword(s):

Vegetation Cover ◽

Turning Point ◽

Temporal Dynamics ◽

Driving Forces ◽

Climatic Factors ◽

Pearson Correlation ◽

Northern China ◽

Climatic Variables ◽

Series Data ◽

Gimms Ndvi

Abstract Aims Recent warmer and wetter climate in northern China remains a hot topic in recent years, yet its effect on vegetation growth has not been fully understood. This study investigated the temporal change of vegetation cover and its correlations with climatic variables from 1982 to 2018 for grasslands in northern China. Our aim is to clarify whether the warmer and wetter climate in recent years drives the greening of the vegetation in this region. Methods We investigated the temporal dynamic of vegetation Normalized Difference Vegetation Index (NDVI) and its driving forces based on long time-series data. Piecewise regression was used to examine whether there was a turning point of the trend of NDVI and climatic variables. Pearson correlation analyses were conducted to quantify the relationship between NDVI and climatic factors. Stepwise multivariable regression was used to quantify the contributions of climate variables to the temporal variations in NDVI. Important Findings We found a turning point of NDVI trend in 2008, with GIMMS NDVI indicating a slight increase of 0.00022 yr -1 during 1982-2008 to an increase of 0.002 yr -1 for GIMMS NDVI during 2008-2015 and 0.0018 yr -1 for MODIS NDVI during 2008-2018. Precipitation was the predominant driver, and air temperature and vapor pressure deficit (VPD) exerted a minor impact on the temporal dynamics of NDVI. Overall, our results suggest a turning point of NDVI trend, and that recent warmer and wetter climate has caused vegetation greening, which provides insights for better predicting the vegetation cover in this region under changing climate.

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Analysis on vegetation cover changes and the driving factors in the mid-lower reaches of Hanjiang River Basin between 2001 and 2015

Open Geosciences ◽

10.1515/geo-2020-0259 ◽

2021 ◽

Vol 13 (1) ◽

pp. 675-689

Author(s):

Yunjun Zhan ◽

Jiemeng Fan ◽

Tingting Meng ◽

Zhongwu Li ◽

Yan Yan ◽

...

Keyword(s):

River Basin ◽

Human Activities ◽

Vegetation Cover ◽

Vegetation Change ◽

Climatic Factors ◽

Driving Factors ◽

Jianghan Plain ◽

Hanjiang River ◽

The Impact ◽

Positive Effect

Abstract The mid-lower reaches of the Hanjiang River Basin, located in the core of economic development in Hubei Province, is an integral part of the Yangtze River Economic Belt. In recent years, the watershed ecosystem has become more sensitive to climate changes and human activities, thus affecting the regional vegetation cover. To maintain a stable watershed ecosystem, it is critical to analyze and evaluate the vegetation change and its response to temperature, precipitation, and human activities in this region. This study, based on the trend analysis, partial correlation analysis, and residual analysis, evaluated the change characteristics of vegetation cover as well as the corresponding driving factors in the basin from 2001 to 2015. The results showed that (1) the overall spatial pattern of vegetation cover in the study area was “high in the west and north, lower on both sides of Hanjiang River, and lowest in the center and southeast,” and the pattern changed parabolically with the increasing elevation. (2) Over the 15 years, vegetation cover in the basin showed an increasing trend, and the increased and decreased areas were 90.72 and 9.23%, respectively. (3) The response of vegetation cover to climatic factors varies greatly depending on the increasing elevation. That is, the lag effect under the impact of temperature disappeared gradually, while it became more evident under the impact of precipitation. (4) On the whole, human activities had a positive effect on the regional vegetation cover. The negative effect in the areas around the Nanyang Basin and the positive effect in most parts of the Jianghan Plain were gradually decreased.

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Quantifying human impacts on hydrological drought using a combined modelling approach in a tropical river basin in Central Vietnam

10.5194/hess-2017-86 ◽

2017 ◽

Author(s):

A. B. M Firoz ◽

Alexandra Nauditt ◽

Manfred Fink ◽

Lars Ribbe

Keyword(s):

River Basin ◽

Reservoir Operation ◽

Human Impacts ◽

Hydrological Drought ◽

Drought Risk ◽

Climatic Data ◽

Strong Impact ◽

Hydropower Development ◽

Drought Duration ◽

Central Vietnam

Abstract. Hydrological droughts are one of the most damaging disasters in terms of economic loss in Central Vietnam and other regions of South East Asia severely affecting agricultural production and drinking water supply. Their increasing frequency and severity can be attributed to extended dry spells and increasing water abstractions for e.g. irrigation and hydropower development to meet the demand of dynamic socioeconomic development. Based on hydro-climatic data for the period from 1980 to 2013 and reservoir operation data, the impacts of recent hydropower development and other alterations of the hydrological network on downstream streamflow and drought risk were assessed for a mesoscale basin of steep topography in Central Vietnam, the Vu Gia Thu Bon (VGTB) river basin. The Just Another Modelling System (JAMS)/J2000 was calibrated for the VGTB river basin to simulate reservoir inflow and the naturalized discharge time series for the downstream gauging stations. The HEC-ResSim reservoir operation model simulated reservoir outflow from eight major hydropower stations as well as the reconstructed streamflow for the main river branches Vu Gia and Thu Bon. Drought duration, severity and frequency was analysed for different time scales for the naturalized and reconstructed streamflow by applying the daily varying threshold method. Efficiency statistics for both models show good results. A strong impact of reservoir operation on downstream discharge at the daily, monthly, seasonal and annual scale was detected for four discharge stations relevant for downstream water allocation. In accordance with the reports from local stakeholders, we found a stronger hydrological drought risk for the anthropogenically impacted reconstructed streamflow. We conclude that the calibrated model setup provides a valuable tool to quantify the different origins of drought to support cross-sectorial water management and planning in a suitable way to be transferred to similar river basins.

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Comparison of Two Different Calculation Methods of Fractional Vegetation Cover

E3S Web of Conferences ◽

10.1051/e3sconf/202129003009 ◽

2021 ◽

Vol 290 ◽

pp. 03009

Author(s):

Liao kaitao

Keyword(s):

Soil Erosion ◽

South China ◽

Time Variation ◽

Vegetation Cover ◽

Fusion Method ◽

Calculation Methods ◽

Fractional Vegetation Cover ◽

High Level ◽

Erosion Equation ◽

Typical Soil

Fractional Vegetation Cover (FVC) is an important parameter for soil erosion equation. The Fractional Vegetation Cover of typical soil erosion county in red soil region of South China was calculated by parameter revision method (PRM) and fusion method (FM).The results of the two methods were compared from two parts of FVC level and 24 half-months FVC. The results show that the FVC level calculated by PRM was concentrated in high level, and that calculated by FM is mainly in medium-high level and high level. The time variation of FVC in 24 half-months calculated by the two methods was the same, but the majority of FVC value calculated by PRM was higher than that calculated by FM. It is better to choose FM method to calculate FVC in estimating soil erosion.

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DISTRIBUTION OF SIVERS APPLES IN THE TERRITORY OF THE TARBAGATAI STATE NATIONAL NATURAL PARK

Globus ◽

10.52013/2658-5197-64-7-1 ◽

2021 ◽

Vol 7 (7(64)) ◽

pp. 3-9

Author(s):

Kabievna Alemseitova Zhanylkhan ◽

Galуmovna Kuanyshbaeva Meruert ◽

Sikimbaevna Saparova Gulnara ◽

Vasily Vladimirovich Polevik

Keyword(s):

Vegetation Cover ◽

Gene Pool ◽

Climatic Factors ◽

The State ◽

Original Form ◽

Malus Sieversii ◽

Natural Park ◽

Current Task ◽

Phenological Monitoring

The current task in the study of Malus sieversii is the balanced use and protection, conservation, reforestation of the vegetation cover. Malus sieversii is a valuable gene pool on the territory of the State National Natural Park «Tarbagatai», therefore, the study, preservation of its form diversity is necessary for modern and future breeding, reforestation, afforestation. In order to preserve Malus sieversii in its original form, phenological monitoring of environmental, anthropogenic, natural and climatic factors of conditions affecting it is carried out and studied. An important role in increasing the productivity, quality and sustainability of Malus sieversii plantings is played by methods of conducting phenological monitoring control throughout the year, for many years.

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