scholarly journals Variation of runoff between southern and northern China and their attribution in the Qinling Mountains, China

2021 ◽  
Author(s):  
Yi He ◽  
Yiyi Hu ◽  
Jinxi Song ◽  
Xiaohui Jiang
Keyword(s):  
Climate Change ◽  
Land Surface ◽  
Potential Evapotranspiration ◽  
Transitional Zone ◽  
Qinling Mountains ◽  
The South ◽  
River Watershed ◽  
Attribution Analysis ◽  
Runoff Reduction ◽  
Runoff Changes

Climate and underlying surface changes have a profound impact on runoff in the Qinling Mountains. This study attempts to identify the difference in runoff changes of two rivers in the south and north of China’s south-north transitional zone under climate change. The Pettit test and Mann-Kendall test were used to investigate the abrupt change and trend analysis on runoff in the Ba River watershed and Jinqian River watershed from 1960 to 2014. The coupled energy-water balance equation based on the Budyko hypothesis estimated the climate and landscape elasticity of runoff followed by attribution analysis of runoff in these two watersheds. The results showed that annual runoff in the Jinqian River (in the southern Qinling Mountains) and the Ba River (in the northern Qinling Mountains) exhibited a significant decreasing trend at P<0.05 and P<0.01, respectively. Abrupt runoff changes occurred in 1989 and 1992 in the Ba River and Jinqian River, respectively. The attribution analysis showed that the change in potential evapotranspiration had little impact on runoff in the southern and northern Qinling Mountains. In contrast, the dominant factors leading to runoff reduction were the change in precipitation and catchment landscape. The contributions of climate change and land surface alteration to runoff changes in the Ba River watershed and Jinqian watershed were 38.08% and 61.92%, and 23.95% and 76.05%, respectively. This study can provide a scientific reference for water resource protection in the south-north transitional zone.

A simple approach to mimic the effect of active vegetation in hydrological models to better estimate hydrological variables under climate change

2021 ◽  
Author(s):  
Thedini Asali Peiris ◽  
Petra Döll
Keyword(s):  
Climate Change ◽  
Land Surface ◽  
Climate Models ◽  
Potential Evapotranspiration ◽  
Global Climate ◽  
Global Climate Models ◽  
Hydrological Models ◽  
Net Radiation ◽  
Ensemble Mean ◽  
The Impact

&lt;p&gt;Unlike global climate models, hydrological models cannot simulate the feedbacks among atmospheric processes, vegetation, water, and energy exchange at the land surface. This severely limits their ability to quantify the impact of climate change and the concurrent increase of atmospheric CO&lt;sub&gt;2&lt;/sub&gt; concentrations on evapotranspiration and thus runoff. Hydrological models generally calculate actual evapotranspiration as a fraction of potential evapotranspiration (PET), which is computed as a function of temperature and net radiation and sometimes of humidity and wind speed. Almost no hydrological model takes into account that PET changes because the vegetation responds to changing CO&lt;sub&gt;2&lt;/sub&gt; and climate. This active vegetation response consists of three components. With higher CO&lt;sub&gt;2&lt;/sub&gt; concentrations, 1) plant stomata close, reducing transpiration (physiological effect) and 2) plants may grow better, with more leaves, increasing transpiration (structural effect), while 3) climatic changes lead to changes in plants growth and even biome shifts, changing evapotranspiration. Global climate models, which include dynamic vegetation models, simulate all these processes, albeit with a high uncertainty, and take into account the feedbacks to the atmosphere.&lt;/p&gt;&lt;p&gt;Milly and Dunne (2016) (MD) found that in the case of RCP8.5 the change of PET (computed using the Penman-Monteith equation) between 1981- 2000 and 2081-2100 is much higher than the change of non-water-stressed evapotranspiration (NWSET) computed by an ensemble of global climate models. This overestimation is partially due to the neglect of active vegetation response and partially due to the neglected feedbacks between the atmosphere and the land surface.&lt;/p&gt;&lt;p&gt;The objective of this paper is to present a simple approach for hydrological models that enables them to mimic the effect of active vegetation on potential evapotranspiration under climate change, thus improving computation of freshwater-related climate change hazards by hydrological models. MD proposed an alternative approach to estimate changes in PET for impact studies that is only a function of the changes in energy and not of temperature and achieves a good fit to the ensemble mean change of evapotranspiration computed by the ensemble of global climate models in months and grid cells without water stress. We developed an implementation of the MD idea for hydrological models using the Priestley-Taylor equation (PET-PT) to estimate PET as a function of net radiation and temperature. With PET-PT, an increasing temperature trend leads to strong increases in PET. Our proposed methodology (PET-MD) helps to remove this effect, retaining the impact of temperature on PET but not on long-term PET change.&lt;/p&gt;&lt;p&gt;We implemented the PET-MD approach in the global hydrological model WaterGAP2.2d. and computed daily time series of PET between 1981 and 2099 using bias-adjusted climate data of four global climate models for RCP 8.5. We evaluated, computed PET-PT and PET-MD at the grid cell level and globally, comparing also to the results of the Milly-Dunne study. The global analysis suggests that the application of PET-MD reduces the PET change until the end of this century from 3.341 mm/day according to PET-PT to 3.087 mm/day (ensemble mean over the four global climate models).&lt;/p&gt;&lt;p&gt;Milly, P.C.D., Dunne K.A. (2016). DOI:10.1038/nclimate3046.&lt;/p&gt;

scholarly journals Contribution Analysis of the Spatial-Temporal Changes in Streamflow in a Typical Elevation Transitional Watershed of Southwest China over the Past Six Decades

Forests ◽  
2019 ◽  
Vol 10 (6) ◽  
pp. 495 ◽  
Author(s):  
Chengcheng Meng ◽  
Huilan Zhang ◽  
Yujie Wang ◽  
Yunqi Wang ◽  
Jian Li ◽  
...  
Keyword(s):  
Land Surface ◽  
Southwest China ◽  
Potential Evapotranspiration ◽  
Influencing Factor ◽  
Climate Impacts ◽  
Spatial And Temporal Scales ◽  
Attribution Analysis ◽  
Land Surface Parameter ◽  
The Impact

Attribution analyses on streamflow variation to changing climate and land surface characteristics are critical in studies of watershed hydrology. However, attribution results may differ greatly on different spatial and temporal scales, which has not been extensively studied previously. This study aims to investigate the spatial-temporal contributions of climate change and underlying surface variation to streamflow alteration using Budyko framework. Jiangling River Watershed (JRW), a typical landform transitional watershed in Southwest China, was chosen as the study area. The watershed was firstly divided into eight sub-basins by hydrologic stations, and hydrometeorological series (1954–2015) were divided into sub-intervals to discriminate spatial-temporal features. The results showed that long-term tendencies of hydrometeorological variables, i.e., precipitation (P), potential evapotranspiration (E0), and runoff depth (R), exhibited clear spatial patterns, which were highly related to topographic characteristics. Additionally, sensitivity analysis, which interpreted the effect of one driving factor by unit change, showed that climate factors P and E0, and catchment characteristics (land surface parameter n) played positive, negative, and negative roles in R, according to elastic coefficients (ε), respectively. The spatial distribution of ε illustrated a greater sensitivity and heterogeneity in the plateau and semi-humid regions (upstream). Moreover, the results from attribution analysis showed that the contribution of the land surface factor accounted for approximately 80% of the R change for the entire JRW, with an obvious spatial variation. Furthermore, tendencies of the contribution rates demonstrated regulations across different sub-regions: a decreasing trend of land surface impacts in trunk stream regions and increasing tendencies in tributary regions, and vice versa for climate impacts. Overall, both hydrometeorological variables and contributions of influencing factors presented regularities in long-term tendencies across different sub-regions. More particularly, the impact of the primary influencing factor on all sub-basins exhibited a decreasing trend over time. The evidence that climate and land surface change act on streamflow in a synergistic way, would complicate the attribution analysis and bring a new challenge to attribution analysis.

scholarly journals Trend and Attribution Analysis of Runoff Changes in the Weihe River Basin in the Last 50 Years

Water ◽  
2021 ◽  
Vol 14 (1) ◽  
pp. 47
Author(s):  
Junjie Xu ◽  
Xichao Gao ◽  
Zhiyong Yang ◽  
Tianyin Xu
Keyword(s):  
River Basin ◽  
Potential Evapotranspiration ◽  
Underlying Surface ◽  
Base Period ◽  
Surface Parameter ◽  
Attribution Analysis ◽  
Runoff Changes ◽  
Increasing Trend ◽  
Weihe River ◽  
Weihe River Basin

In recent years, the Weihe River basin has experienced dramatic changes and a sharp decrease in runoff, which has constrained the sustainable development of the local society, economy, and ecology. Quantitative attribution analysis of runoff changes in the Weihe River basin can help to illustrate reasons for dramatic runoff changes and to understand its complex hydrological response. In this paper, the trends of hydrological elements in the Weihe River basin from 1970 to 2019 were systematically analyzed using the M–K analysis method, and the effects of meteorological elements and underlying surface changes on runoff were quantitatively analyzed using the Budyko theoretical framework. The results show that potential evapotranspiration and precipitation in the Weihe River basin have no significant change in 1970–2019; runoff depth has an abrupt change around 1990 and then decrease significantly. The study period is divided into the base period (1970–1989), PΙ (1990–2009), and PII (2010–2019). Compared with the base period, the elasticity coefficients (absolute values) of each element show an increasing trend in PΙ and PII. The sensitivity of runoff to these coefficients is increasing. The sensitivity of the precipitation is the highest (2.72~3.17), followed by that of the underlying surface parameter (−2.01~−2.35); the sensitivity of the potential evapotranspiration is the weakest (−1.72~−2.17). In the PΙ period, the runoff depth decreased significantly due to the combination effects of precipitation and underlying surface with the values of 6.18 mm and 13.92 mm, respectively. In the PII period, rainfall turned to an increasing trend, contributing to the increase in runoff by 11.80 mm; the further increase in underlying surface parameters was the main reason for the decrease in runoff by 22.19 mm. The significant increase in runoff by 8.54 mm because of the increased rainfall, compared with the PΙ periods. Overall, the increasing underlying surface parameter makes the largest contribution to the runoff changes while the precipitation change is also an important factor.

scholarly journals Hourly potential evapotranspiration at 0.1° resolution for the global land surface from 1981-present

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Michael Bliss Singer ◽  
Dagmawi Teklu Asfaw ◽  
Rafael Rosolem ◽  
Mark O. Cuthbert ◽  
Diego G. Miralles ◽  
...  
Keyword(s):  
Climate Change ◽  
Seasonal Variations ◽  
Land Surface ◽  
Hydrological Cycle ◽  
Potential Evapotranspiration ◽  
Evaporative Demand ◽  
Reanalysis Dataset ◽  
Turn On ◽  
Global Land ◽  
Time Frames

AbstractChallenges exist for assessing the impacts of climate and climate change on the hydrological cycle on local and regional scales, and in turn on water resources, food, energy, and natural hazards. Potential evapotranspiration (PET) represents atmospheric demand for water, which is required at high spatial and temporal resolutions to compute actual evapotranspiration and thus close the water balance near the land surface for many such applications, but there are currently no available high-resolution datasets of PET. Here we develop an hourly PET dataset (hPET) for the global land surface at 0.1° spatial resolution, based on output from the recently developed ERA5-Land reanalysis dataset, over the period 1981 to present. We show how hPET compares to other available global PET datasets, over common spatiotemporal resolutions and time frames, with respect to spatial patterns of climatology and seasonal variations for selected humid and arid locations across the globe. We provide the data for users to employ for multiple applications to explore diurnal and seasonal variations in evaporative demand for water.

scholarly journals Attribution Analysis of Runoff Variation in the Yue River Watershed of the Qinling Mountains

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Yiyi Hu ◽  
Yi He
Keyword(s):  
Climate Change ◽  
Annual Runoff ◽  
Test Method ◽  
Underlying Surface ◽  
Qinling Mountains ◽  
Elastic Coefficient ◽  
Surface Change ◽  
River Watershed ◽  
Runoff Change ◽  
Runoff Decrease

In recent decades, global climate change, especially human activities, has led to profound changes in the hydrological cycle and hydrological processes in watersheds. Taking the Yue River watershed in the Qinling Mountains in China as the study area, the Mann–Kendall test and Pettitt mutation test method were used to analyze the various characteristics of hydrological and climatic elements from 1960 to 2018. Then, the elastic coefficient method based on the Budyko framework was used to estimate the elastic coefficient of runoff change on each influencing factor. The results showed that the annual runoff decreased at a rate of 0.038 × 108 m3/a ( P > 0.05 ), and a significant abrupt change occurred in 1990. The annual precipitation and potential evapotranspiration (ET0) increased and decreased, with change rates of 0.614 mm/a and −0.811 mm/a ( P > 0.05 ), respectively. The elasticity coefficients of precipitation, ET0, and the underlying surface were 1.95, −0.95, and −0.85, respectively, indicating that annual runoff was most sensitive to the change in precipitation, followed by the change in ET0, and had the lowest sensitivity to the change in the underlying surface. Underlying surface change is the main factor of runoff decrease; the contribution is 89.07%. The total contribution of climate change to runoff change is 10.93%, in which the contributions of precipitation and ET0 are 17.59% and −6.66%, respectively. The NDVI reflecting underlying surface change has been increasing since 1990, which is an important reason for the runoff decrease.

scholarly journals Specific Drivers and Responses to Land Surface Phenology of Different Vegetation Types in the Qinling Mountains, Central China

2021 ◽  
Vol 13 (22) ◽  
pp. 4538
Author(s):  
Jiaqi Guo ◽  
Xiaohong Liu ◽  
Wensen Ge ◽  
Xiaofeng Ni ◽  
Wenyuan Ma ◽  
...  
Keyword(s):  
Climate Change ◽  
Land Surface ◽  
Meteorological Factors ◽  
Growing Season ◽  
Central China ◽  
Shortwave Radiation ◽  
Qinling Mountains ◽  
Vegetation Types ◽  
Land Surface Phenology ◽  
Vegetation Growth

Land surface phenology (LSP), as a precise bio-indicator that responds to climate change, has received much attention in fields concerned with climate change and ecology. Yet, the dynamics of LSP changes in the Qinling Mountains (QMs)—A transition zone between warm-temperate and north subtropical climates with complex vegetation structure—under significant climatic environmental evolution are unclear. Here, we analyzed the spatiotemporal dynamics of LSP for different vegetation types in the QMs from 2001 to 2019 and quantified the degree of influence of meteorological factors (temperature, precipitation, and shortwave radiation), and soil (temperature and moisture), and biological factors (maximum of NDVI and middle date during the growing season) on LSP changes using random forest models. The results show that there is an advanced trend (0.15 days/year) for the start of the growing season (SOS), a delayed trend (0.24 days/year) for the end of the growing season (EOS), and an overall extended trend (0.39 days/year) for the length of the growing season (LOS) in the QMs over the past two decades. Advanced SOS and delayed EOS were the dominant patterns leading to a lengthened vegetation growing season, followed by a joint delay of SOS and EOS, and the latter was particularly common in shrub and evergreen broadleaved forests. The growth season length increased significantly in western QMs. Furthermore, we confirmed that meteorological factors are the main factors affecting the interannual variations in SOS and EOS, especially the meteorological factor of preseason mean shortwave radiation (SWP). The grass and crop are most influenced by SWP. The soil condition has, overall, a minor influence the regional LSP. This study highlighted the specificity of different vegetation growth in the QMs under warming, which should be considered in the accurate prediction of vegetation growth in the future.

scholarly journals Attribution of Runoff Variation in the Headwaters of the Yangtze River Based on the Budyko Hypothesis

2019 ◽  
Vol 16 (14) ◽  
pp. 2506 ◽  
Author(s):  
Junlong Liu ◽  
Jin Chen ◽  
Jijun Xu ◽  
Yuru Lin ◽  
Zhe Yuan ◽  
...  
Keyword(s):  
Climate Change ◽  
Water Resource ◽  
Change Point ◽  
Human Activities ◽  
Yangtze River ◽  
Potential Evapotranspiration ◽  
Test Method ◽  
The Yangtze River ◽  
Runoff Changes ◽  
Runoff Depth

Quantifying the contributions of climate change and human activities on runoff changes is of great importance for water resource management, sustainable water resource utilization, and sustainable development of society. In this study, hydrological and climatic data from hydrological and meteorological stations in the headwaters of the Yangtze River (YRHA) from 1966 to 2013 were used to quantitatively attribute the runoff change to the impacts of climate change and human activities separately. Firstly, the change trends in precipitation, runoff depth and potential evapotranspiration were analyzed by the Mann-Kendall test method. Three methods, secondly, including ordered clustering, Mann-Kendall and cumulative anomaly curve were adopted to detect the change points of runoff at Zhimenda hydrological station and partition the whole study period into two sub-periods at the change point (base and impacted periods). Then, the elasticity coefficient method based on the Budyko hypothesis was applied to calculate elasticity coefficients of runoff to precipitation, potential evapotranspiration and land use/cover during the two periods, and to evaluate the contributions of climate change and human activities. Results indicated that during 1966–2013, runoff depth, precipitation and potential evapotranspiration all showed a significant increasing trend, with increasing rates of 7.26 mm decade−1, 18.725 mm decade−1 and 7.228 mm decade−1, respectively. One change point (2004) was detected for the annual runoff, and 1966–2003 and 2004–2013 were respectively identified as base and impacted periods. The results of elasticity coefficients showed that the runoff depth was most sensitive to the change of precipitation during the two periods. The relative contributions of precipitation, potential evapotranspiration and parameter n to runoff changes were 99.7%, −6.08% and 3.88%, respectively. Furthermore, the coupled contribution rate of other factors was less than 2.5%. Generally, results indicated that precipitation is the main factor on the historical runoff changes in this basin.

scholarly journals Identifying dominant component of runoff yield processes: a case study in a sub-basin of the middle Yellow River

2021 ◽  
Author(s):  
Li Zhang ◽  
Caihong Hu ◽  
Shengqi Jian ◽  
Qiang Wu ◽  
Guang Ran ◽  
...  
Keyword(s):  
Climate Change ◽  
Water Conservation ◽  
Human Activities ◽  
Large Scale ◽  
Overland Flow ◽  
Yellow River ◽  
Potential Evapotranspiration ◽  
Subsurface Flow ◽  
Runoff Generation ◽  
Runoff Reduction

Abstract The effects of long-term natural climate change and human activities on runoff generation mechanism in the middle Yellow River Basin are long-standing concerns. This study analyzed the characteristics of hydro-climatic variables in the meso-scale Tuweihe catchment based on the observed data for the period 1956–2016 and a climate elastic method. The spatial distribution of dominant runoff processes (DRP) following land use changes in case of rainfall was identified. The results show significant decreasing trends in annual runoff, whereas slightly downward trends are identified for annual precipitation and potential evapotranspiration, 1984 is detected as the mutation year of the study period. The average contributions of climate change and human activities to the runoff reduction in the Tuweihe catchment were 33.2% and 66.8%, respectively. In general, the influences of human activities on runoff are applied mostly through the alteration of the catchment characteristics. The dominant runoff processes changes between 1980 and 2015 show significant effects of large-scale soil and water conservation measures in the Tuweihe catchment. We found that Hortonian overland flow (HOF) and fast subsurface flow (SSF1) were the two main processes in 1980 (30.3% and 34.4% respectively), but the proportion of HOF decreased by 9.6% in 2015. The proportions of saturation overland flow (SOF) and SSF have increased to varying degrees, which means that the catchment is more prone to generate subsurface flow processes. Consequently, under similar rainfall conditions, the runoff yield of flood events decreases in the second period.

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