Copula-Based Abrupt Variations Detection in the Relationship of Seasonal Vegetation-Climate in the Jing River Basin, China

Understanding the changing relationships between vegetation coverage and precipitation/temperature (P/T) and then exploring their potential drivers are highly necessary for ecosystem management under the backdrop of a changing environment. The Jing River Basin (JRB), a typical eco-environmentally vulnerable region of the Loess Plateau, was chosen to identify abrupt variations of the relationships between seasonal Normalized Difference Vegetation Index (NDVI) and P/T through a copula-based method. By considering the climatic/large-scale atmospheric circulation patterns and human activities, the potential causes of the non-stationarity of the relationship between NDVI and P/T were revealed. Results indicated that (1) the copula-based framework introduced in this study is more reasonable and reliable than the traditional double-mass curves method in detecting change points of vegetation and climate relationships; (2) generally, no significant change points were identified during 1982–2010 at the 95% confidence level, implying the overall stationary relationship still exists, while the relationships between spring NDVI and P/T, autumn NDVI and P have slightly changed; (3) teleconnection factors (including Arctic Oscillation (AO), Pacific Decadal Oscillation (PDO), Niño 3.4, and sunspots) have a more significant influence on the relationship between seasonal NDVI and P/T than local climatic factors (including potential evapotranspiration and soil moisture); (4) negative human activities (expansion of farmland and urban areas) and positive human activities (“Grain For Green” program) were also potential factors affecting the relationship between NDVI and P/T. This study provides a new and reliable insight into detecting the non-stationarity of the relationship between NDVI and P/T, which will be beneficial for further revealing the connection between the atmosphere and ecosystems.

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Quantifying the Influences of Natural Factors and Human Activities on NDVI Changes in the Hanjiang River Basin, China

Remote Sensing ◽

10.3390/rs12223780 ◽

2020 ◽

Vol 12 (22) ◽

pp. 3780

Author(s):

Ting Chen ◽

Jun Xia ◽

Lei Zou ◽

Si Hong

Keyword(s):

River Basin ◽

Human Activities ◽

Urban Areas ◽

Vegetation Index ◽

Vegetation Coverage ◽

Vegetation Growth ◽

Natural Factors ◽

Range Type ◽

Hanjiang River ◽

The Impact

The Hanjiang River Basin (HJRB) is an important source area for drinking water in Hubei Province, China, and the vegetation coverage there is important to the ecological system. Due to the spatial heterogeneity and synergistic effect of various factors, it is very difficult to identify the main factors affecting vegetation growth in the HJRB. With the normalized difference vegetation index (NDVI) data from 2001 to 2018 in the HJRB, the spatiotemporal patterns of NDVI and the influences of natural factors and human activities on NDVI were investigated and quantified based on the Mann-Kendall (M-K) test, partial correlation analysis, and Geographical Detector. The individual factors and their interactions and the range/type of factor attributes suitable for vegetation growth were also examined. NDVI in the HJRB increased from 2001 to 2018, and the variation rate was 0.0046 year−1. NDVI was increasing in 81.17% of the area (p < 0.05). Elevation and slope can effectively explain the vegetation distribution. The interactions of factors on NDVI were significant, and the interactions of the elevation and precipitation can maximize the impact among all factors. The range of available landforms is thought to be highly conducive to vegetation growth. The rates of the annual precipitation and annual mean temperature changed from 2001 to 2018, which were 3.665 mm/year and 0.017 °C/year, and the regions where NDVI positively correlated with them were over 85%. Contrary to the general trend, NDVI has obviously decreased in urban areas since 2010. The quantitative findings of this study can help us better understand the effects of various factors on vegetation growth and provide appropriate suggestions for vegetation protection and restoration in the HJRB.

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Variations in the precipitation–runoff relationship of the Weihe River Basin

Hydrology Research ◽

10.2166/nh.2016.032 ◽

2016 ◽

Vol 48 (1) ◽

pp. 295-310 ◽

Cited By ~ 13

Author(s):

Aijun Guo ◽

Jianxia Chang ◽

Dengfeng Liu ◽

Yimin Wang ◽

Qiang Huang ◽

...

Keyword(s):

River Basin ◽

Human Activities ◽

Driving Forces ◽

Potential Evapotranspiration ◽

Annual Runoff ◽

Change Points ◽

Archimedean Copulas ◽

Significance Level ◽

Weihe River ◽

Weihe River Basin

The main goal of this study is to introduce the Archimedean copulas, which overcome the low accuracy and subjective nature of the traditional double mass curve method, to investigate the precipitation–runoff relationship (PRR) and detect change points in the Weihe River Basin (WRB). With the construction of a joint distribution between precipitation and runoff by the Archimedean copulas, a statistical variable considering the distribution parameter was estimated to judge the change point of the PRR. The results show that: (1) annual precipitation and runoff present decreasing trends that are significant and insignificant, respectively, at the 95% significance level, while annual potential evapotranspiration (PET) increases slightly; (2) change points of the PRR occurred in 1971 and 1994; (3) the annual runoff changed more dramatically than precipitation during the periods from 1972 to 1994 and 1995 to 2010 compared with 1960–1971, which indicates that in addition to precipitation, there are some other non-precipitation factors that are responsible for the change in the PRR; and (4) the contributions to runoff from human activities declined from 1972 to 1994 (84.15%) and 1995 to 2010 (57.16%). These results suggest that human activities (e.g., irrigation, reservoirs, water-and-soil conservation) were the primary driving forces leading to changes in the PRR in the WRB.

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Physiographic controls on pre-event hydrological states and hydrological response to extreme precipitation in the Alzette River Basin, Luxembourg

10.5194/egusphere-egu2020-8954 ◽

2020 ◽

Author(s):

Carol Tamez-Melendez ◽

Judith Meyer ◽

Audrey Douinot ◽

Günter Blöschl ◽

Laurent Pfister

Keyword(s):

Land Use ◽

River Basin ◽

Urban Areas ◽

Large Scale ◽

Western Europe ◽

Flash Flood ◽

Potential Evapotranspiration ◽

Hydrological Regime ◽

Area Of Interest ◽

Wide Range

The hydrological regime of rivers in Luxembourg (Central Western Europe) is characterised by summer low flows and winter high flows. In winter, large-scale floods are typically triggered by long-lasting sequences of precipitation events, related to westerly atmospheric fluxes that carry wet and temperate air masses from the Atlantic Ocean. In recent years, several flash flood events have been observed in Luxembourg. While being a common feature of Mediterranean river basins, this type of flooding events is uncommon at higher latitudes. The design of the hydro-meteorological monitoring and forecasting systems operated in Luxembourg is not adapted to this type of extreme events and there is a pressing need for a better mechanistic understanding of flash flood triggering mechanisms.Here, we explore two lines of research &#8211; focusing on (i) the spatio-temporal variability of flash flood generation across a set of 41 nested catchments covering a wide range of physiographic settings (with mixed land use, soil types and bedrock geology) and (ii) the responsivity (resistance) and elasticity (resilience) of these catchments to global change.Our area of interest is the S&#251;re River basin (4,240 km2), characterised by a homogenous climate (temperate oceanic), as well as various bedrock (e.g. sandstone, marls, shale) and land use (e.g. forests, grassland, crops, urban areas) types. Based on 8 years&#8217; worth of daily hydrological data (precipitation, discharge and potential evapotranspiration) we computed the increments of the water balance to determine the maximum storage capacity and pre-event wetness state (expressed as storage deficit). Based on the relationship between storage deficit and discharge we first estimated total storage at nearly zero flow conditions. Second, we compared event runoff ratios (Q/P) to pre-hydrological states (as expressed to storage deficit prior to a rainfall-runoff event) in order to assess each catchment&#8217;s sensitivity to antecedent wetness conditions. Third, we assessed the responsivity (resistance) and elasticity (resilience) to climate variations &#8211; as expressed through the PET/P and AET/P deviations from the Budyko curve &#8211; for each individual catchment. Finally, we investigated potential physiographic controls on catchment responsivity and elasticity across our set of 41 nested catchments.

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Effects of Hydro-Meteorological Factors on Streamflow Withdrawal for Irrigation in Yeongsan River Basin

Sustainability ◽

10.3390/su13094969 ◽

2021 ◽

Vol 13 (9) ◽

pp. 4969

Author(s):

Jang Hyun Sung ◽

Donghae Baek ◽

Young Ryu ◽

Seung Beom Seo ◽

Kee-Won Seong

Keyword(s):

River Basin ◽

Water Use ◽

Vegetation Index ◽

Normalized Difference Vegetation Index ◽

Agricultural Land ◽

Potential Evapotranspiration ◽

Standardized Precipitation Index ◽

Water Withdrawal ◽

Irrigation Water Use ◽

The Relationship

The relationships between a variety of hydro-meteorological variables and irrigation water use rates (WUR) were investigated in this study. Standardized Precipitation Index (SPI), Potential Evapotranspiration (PET), and Normalized Difference Vegetation Index (NDVI) were explored to identify the relationship with the WUR. The Yeongsan river basin, the agricultural land of which is mostly occupied by well-irrigated paddy, was used for the pilot study. Four different temporal scales of SPI-3, 6, 9, and 12 were tested, and PET was calculated using the Thornthwaite method. To calculate NDVI, the surface spectral reflectance data, which was acquired by Moderate Resolution Imaging Spectroradiometer (MODIS) equipped on the Terra satellite, were used. As a result, there was a statistically significant relationship between SPI9 and the WUR during drought periods in which negative values of SPI9 were obtained. The WUR was strongly correlated with both PET and NDVI. Compared with SPI, the variability of WUR in this study area was more sensitively affected by PET and NDVI, which can cause a potential lack of agricultural water supply. The finding of this study implies that SPI9, PET, and NDVI are the critical factors for predicting water withdrawal during drought conditions so that they can be used for irrigational water use management. Although a part of the findings of this study has been discussed by a few previous studies, this study is novel in that it quantifies the relationship between these factors using actual field observations of streamflow withdrawal for irrigation.

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Contributions of Vegetation Greening and Climate Change to Evapotranspiration Trend after Large-Scale Vegetation Restoration on the Loess Plateau, China

Water ◽

10.3390/w13131755 ◽

2021 ◽

Vol 13 (13) ◽

pp. 1755

Author(s):

Shuo Wang ◽

Chenfeng Cui ◽

Qin Dai

Keyword(s):

Climate Change ◽

Loess Plateau ◽

Large Scale ◽

Vegetation Index ◽

Normalized Difference Vegetation Index ◽

Potential Evapotranspiration ◽

Development Trend ◽

Future Trend ◽

Natural Ecosystem ◽

The Loess Plateau

Since the early 2000s, the vegetation cover of the Loess Plateau (LP) has increased significantly, which has been fully recorded. However, the effects on relevant eco-hydrological processes are still unclear. Here, we made an investigation on the changes of actual evapotranspiration (ETa) during 2000–2018 and connected them with vegetation greening and climate change in the LP, based on the remote sensing data with correlation and attribution analysis. Results identified that the average annual ETa on the LP exhibited an obvious increasing trend with the value of 9.11 mm yr−1, and the annual ETa trend was dominated by the changes of ETa in the third quarter (July, August, and September). The future trend of ETa was predicted by the Hurst exponent. Partial correlation analysis indicated that annual ETa variations in 87.8% regions of the LP were controlled by vegetation greening. Multiple regression analysis suggested that the relative contributions of potential evapotranspiration (ETp), precipitation, and normalized difference vegetation index (NDVI), to the trend of ETa were 5.7%, −26.3%, and 61.4%, separately. Vegetation greening has a close relationship with the Grain for Green (GFG) project and acts as an essential driver for the long-term development trend of water consumption on the LP. In this research, the potential conflicts of water demanding between the natural ecosystem and social-economic system in the LP were highlighted, which were caused by the fast vegetation expansion.

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Temporal and Spatial Variations in NDVI and Analysis of the Driving Factors in the Desertified Areas of Northern China From 1998 to 2015

Frontiers in Environmental Science ◽

10.3389/fenvs.2021.633020 ◽

2021 ◽

Vol 9 ◽

Author(s):

Xuyang Wang ◽

Yuqiang Li ◽

XinYuan Wang ◽

Yulin Li ◽

Jie Lian ◽

...

Keyword(s):

Ecological Restoration ◽

Large Scale ◽

Vegetation Index ◽

Normalized Difference Vegetation Index ◽

Climatic Factors ◽

Northern China ◽

Gobi Desert ◽

Desert Grassland ◽

Dune Stability ◽

Mobile Dunes

China faces some of the most serious desertification in the world, leading to many problems. To solve them, large-scale ecological restoration projects were implemented. To assess their effectiveness, we analyzed normalized-difference vegetation index (NDVI) data derived from SPOT VEGETATION and gridded climate datasets from 1998 to 2015 to detect the degrees of desertification and the effects of human and climate drivers on vegetation dynamics. We found that NDVI of desertified areas generally decreased before 2000, then increased. The annual increase in NDVI was fixed dunes (0.0013) = semi-fixed dunes (0.0013) > semi-mobile dunes (0.0012) > gobi (gravel) desert (0.0011) > mobile dunes (0.0003) > saline–alkali land (0.0000). The proportions of the area of each desert type in which NDVI increased were fixed dunes (43.4%) > semi-mobile dunes (39.7%) > semi-fixed dunes (26.7%) > saline–alkali land (23.1%) > gobi desert (14.4%) > mobile dunes (12.5%). Thus, the vegetation response to the restoration efforts increased as the initial dune stability increased. The proportion of the area where desertification was dominated by temperature (1.8%) was far less than the area dominated by precipitation (14.1%). However, 67.6% of the change was driven by non-climatic factors. The effectiveness of the ecological restoration projects was significant in the Loess Plateau and in the Mu Us, Horqin, and Hulunbuir sandy lands. In contrast, there was little effect in the Badain Jaran, Ulan Buh, and Tengger deserts; in particular, vegetation cover has declined seriously in the Hunshandake Sandy Land and Alkin Desert Grassland. Thus, more or different ecological restoration must be implemented in these areas.

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Physiographic controls on pre-event hydrological states and hydrological response to extreme precipitation in the Alzette River Basin, Luxembourg

10.5194/egusphere-egu21-15439 ◽

2021 ◽

Author(s):

Carol Tamez Melendez ◽

Judith Meyer ◽

Audrey Douinot ◽

Günter Blöschl ◽

Laurent Pfister

Keyword(s):

River Basin ◽

Large Scale ◽

Flash Flood ◽

Potential Evapotranspiration ◽

Convective Precipitation ◽

Hydrological Response ◽

Local Character ◽

Area Of Interest ◽

Oceanic Climate ◽

Precipitation Events

Flash flood events have caused massive damage on multiple occasions between 2016 and 2018 in several catchments in eastern Luxembourg. This region is very well known for being exposed to large-scale winter floods, commonly triggered by long-lasting advective precipitation events related to westerly atmospheric fluxes. However, flash floods - a truly exceptional phenomenon in this region - are have solely occurred in summer in response to intense convective precipitation events. Thus, because of the rare occurrence and local character of this type of events, the mechanisms eventually controlling a flash flood-type response of a catchment remains poorly understood. &#160;Here, we focus on four main objectives: i) the role that physiographic characteristics play on the spatial variability of pre-event hydrological states (as expressed via storage) across a set of 41 nested catchments located in the S&#251;re River basin (4,240 km2), Luxembourg, ii) the hydrological response to precipitation controlled by those pre-event hydrological states, iii) the responsivity (resistance) and elasticity (resilience) of the catchments to global change, and iv) the relation between water yields and the offsets from Budyko curve and its related energy limits.The area of interest is not only characterised by a homogenous temperate oceanic climate but also by heterogeneous physiographical conditions and land use, which makes it ideal for this study. We used 8 years&#8217; worth hydrological data (precipitation, discharge and potential evapotranspiration) to calculate the increments of the water balance and determine the maximum storage capacity and storage deficits. Second, we used the relationship between storage deficit and discharge to estimate total storage at a hypothetical nearly zero flow condition. Third, we compared the pre-hydrological states and event runoff ratios (Q/P) to the catchments&#8217; physiographical conditions in order to link catchment&#8217;s sensitivity to storage metrics. We then assessed the responsivity and elasticity to climate and anthropogenic variations &#8211; as expressed through the PET/P and AET/P deviations from the Budyko curve and energy limits&#8211; for each individual catchment. Finally, we investigated the catchment&#8217;s area control on responsivity, elasticity, water yields and Budyko&#8217;s elements across our set of 41 nested catchments.

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Sensitivity analysis of potential evapotranspiration to key climatic factors in the Shiyang River Basin

Journal of Water and Climate Change ◽

10.2166/wcc.2020.225 ◽

2020 ◽

Author(s):

Xuelei Zhang ◽

Weihua Xiao ◽

Yicheng Wang ◽

Yan Wang ◽

Miaoye Kang ◽

...

Keyword(s):

Sensitivity Analysis ◽

River Basin ◽

Air Temperature ◽

Climatic Factors ◽

Potential Evapotranspiration ◽

Mountainous Region ◽

Shiyang River Basin ◽

Increasing Trends ◽

Maximum Air Temperature ◽

Monteith Equation

Abstract This paper focuses on determining the spatial and temporal characteristics of the sensitivity coefficients (SCs) between potential evapotranspiration (ET0) and key climatic factors across the Shiyang River Basin (SYRB) from 1981 to 2015. Penman–Monteith equation and a sensitivity analysis were used to calculate ET0 and the SCs for key climatic factors. Sen's slope was used to analyze the observed series. According to the results, the sensitivity significances were in the order of relative humidity (RH) > net solar radiation (NSR) > wind speed (WS) > maximum air temperature (Tmax) > minimum air temperature (Tmin). The SCs for the RH and NSR were larger in the upper mountainous region, while the other three coefficients were larger in the middle and lower reaches. All five climatic factors for the ET0 SCs showed increasing trends in the mountainous region, and the Tmax, WS and RH SCs increased in the middle and lower reaches. Over the past 35 years, the change in ET0 was dominated by the air temperature (T), RH and NSR, and the increase in ET0 during the studied period was mainly due to the increases in T and NSR.

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Attribution Analysis of Hydrological Drought Risk Under Climate Change and Human Activities: A Case Study on Kuye River Basin in China

Water ◽

10.3390/w11101958 ◽

2019 ◽

Vol 11 (10) ◽

pp. 1958 ◽

Cited By ~ 1

Author(s):

Zhang ◽

Wang ◽

Zhou

Keyword(s):

Climate Change ◽

River Basin ◽

Human Activities ◽

Large Scale ◽

Research Area ◽

Drought Severity ◽

Drought Risk ◽

Drought Duration ◽

Recurrence Period ◽

The Impact

This study conducted quantitative diagnosis on the impact of climate change and human activities on drought risk. Taking the Kuye river basin (KRB) in China as the research area, we used variation point diagnosis, simulation of precipitation and runoff, drought risk assessment, and attribution quantification. The results show that: (1) the annual runoff sequence of KRB changed significantly after 1979, which was consistent with the introduction of large-scale coal mining; (2) under the same drought recurrence period, the drought duration and severity in the human activity stage were significantly worse than in the natural and simulation stages, indicating that human activities changed the drought risk in this area; and (3) human activities had little impact on drought severity in the short duration and low recurrence period, but had a greater impact in the long duration and high recurrence period. These results provide scientific guidance for the management, prevention, and resistance of drought; and guarantee sustainable economic and social development in the KRB.

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A Study on the Relationship between Land Use Change and Water Quality of the Mitidja Watershed in Algeria Based on GIS and RS

Sustainability ◽

10.3390/su12093510 ◽

2020 ◽

Vol 12 (9) ◽

pp. 3510 ◽

Cited By ~ 2

Author(s):

Dechao Chen ◽

Acef Elhadj ◽

Hualian Xu ◽

Xinliang Xu ◽

Zhi Qiao

Keyword(s):

Water Quality ◽

Land Use ◽

Land Use Change ◽

River Basin ◽

Agricultural Land ◽

Vegetation Coverage ◽

Water Quality Control ◽

Urban Settlement ◽

The Relationship

Many catchments in northern Algeria, including the coastal Mitidja Basin in the north central part of the country have been negatively affected by the deterioration of water quality in recent years. This study aims to discover the relationship between land use change and its impact on water quality in the coastal Mitidja river basin. Based on the data of land use and water quality in 2000, 2010 and 2017, the relationship between land use change and surface water quality index in the Mitidja Watershed was discussed through GIS and statistical analysis. The results show that the physical and chemical properties of the Mitidja river basin have obvious spatial heterogeneity. The water quality of upstream was better than that of downstream. There was a significant spatial relationship between the eight water quality indicators and three land use types, including urban residential land, agricultural land and vegetation. In most cases, settlements and agricultural land are the dominant factors leading to river pollution, and higher vegetation coverage helps to improve water quality. The regression model revealed that percentage of urban settlement area was a predictor for NH4-N, BOD5, COD, SS, PO4-P, DO and pH, while vegetation was a predictor for NO3-N. The analysis also showed that during this period, urban settlement areas increased sharply, which has a significant impact on water quality variables. Agricultural land only had a significant positive correlation with PO4-P. The results provide an effective way to evaluate river water quality, control water pollution and land use management by landscape pattern.

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