Contributions of Climate Change and Human Activities on Runoff Variations in the Central Part of Tajikistan in Central Asia

Comprehensive studies of the contributions of climate variation and anthropogenic activities to runoff alterations are essential for sustainable management of water resources in Central Asian countries. In the Kofarnihon River Basin (KRB) in Central Asia, both changing climate conditions and anthropogenic activities are known to have caused variations to the hydrological cycle. Therefore, quantifying the net influence of human contribution to the runoff changes is a challenge. In this study, by applying the original and modified Mann–Kendall trend test, Pettitt test, double cumulative curve and elasticity methods the historical trends and breakpoint changes of the hydro-climatic variables including temperature, precipitation, potential evapotranspiration, and runoff over the 1950–2016 along were determined, in addition the contributions of climate variation and anthropogenic activities to runoff changes in the KRB were evaluated. The trend analysis exhibited a significant increasing trend in annual temperature and potential evapotranspiration and the annual precipitation trend showed insignificant decreasing trend during the 1950–2016 time period. The breakpoint change was detected in runoff occurs in 1991. Further, the time series (1950–2016) are separated into the prior impacted period (1950–1991) and post impacted period (1992–2016) with trend test. The results showed that anthropogenic activities played a dominant role in changes in the runoff with a contribution of 79.94% in the upstream and 97.78% in the downstream of the KRB. Climate change contributed to 20.06% in the upstream and 7.53% in the downstream of the catchment during the post impacted period. In the land-use type changes, the dominant role played construction land which showed that the area from 248.63 km2 in 1990 increased to 685.45 km2 (175.69%) in 2015. The findings suggest that it is essential to adopt effective steps for sustainable development of ecological, hydrological and social order in the KRB in Central Asia.

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Quantifying the Relative Contribution of Climate Change and Anthropogenic Activities on Runoff Variations in the Central Part of Tajikistan in Central Asia

Land ◽

10.3390/land10050525 ◽

2021 ◽

Vol 10 (5) ◽

pp. 525

Author(s):

Nekruz Gulahmadov ◽

Yaning Chen ◽

Aminjon Gulakhmadov ◽

Moldir Rakhimova ◽

Manuchekhr Gulakhmadov

Keyword(s):

Climate Change ◽

Central Asia ◽

Potential Evapotranspiration ◽

Anthropogenic Activities ◽

Dominant Role ◽

Upstream Region ◽

Dominant Factor ◽

Relative Contribution ◽

Downstream Region ◽

Runoff Changes

Quantifying the relative contribution of climate change and anthropogenic activities to runoff alterations are essential for the sustainable management of water resources in Central Asian countries. In the Kofarnihon River Basin (KRB) in Central Asia, both changing climate conditions and anthropogenic activities are known to have caused changes to the hydrological cycle. Therefore, quantifying the net influence of anthropogenic contribution to the runoff changes is a challenge. This study applied the original and modified Mann–Kendall trend test, including the Sen’s slope test, Pettitt’s test, double cumulative curve, and elasticity methods. These methods were applied to determine the historical trends, magnitude changes and change points of the temperature, precipitation, potential evapotranspiration, and runoff from 1950 to 2016. In addition, the contributions of climate change and anthropogenic activities to runoff changes in the KRB were evaluated. The trend analysis showed a significant increasing trend in annual temperature and potential evapotranspiration, while the annual precipitation trend showed an insignificant decreasing trend during the 1950–2016 time period. The change point in runoff occurred in 1986 in the upstream region and 1991 in the downstream region. Further, the time series (1950–2016) is separated into the prior impacted period (1950–1986 and 1950–1991) and post impacted period (1987–2016 and 1992–2016) for the upstream and downstream regions, respectively. During the post impacted period, climate change and anthropogenic activities contributed to 87.96% and 12.04% in the upstream region and 7.53% and 92.47% in the downstream region of the KRB. The results showed that in runoff changes, the anthropogenic activities played a dominant role in the downstream (97.78%) and the climate change impacts played a dominant factor in the upstream region (87.96%). In the land-use type changes, the dominant role was played by construction land, which showed that the area from 248.63 km2 in 1990 increased to 685.45 km2 (175.69%) in 2015. These findings suggest that it is essential to adopt effective steps for the sustainable development of the ecological, hydrological, and social order in the KRB in Central Asia.

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Assessment of the impact of climate change on the freshwater availability of Kaduna River basin, Nigeria

Journal of Water and Land Development ◽

10.2478/jwld-2018-0047 ◽

2018 ◽

Vol 38 (1) ◽

pp. 105-114 ◽

Cited By ~ 2

Author(s):

Gloria C. Okafor ◽

Kingsley N. Ogbu

Keyword(s):

Climate Change ◽

River Basin ◽

Water Availability ◽

Hydrological Cycle ◽

Temporal Trends ◽

Kendall Test ◽

Well Being ◽

Trend Test ◽

Climate Indices ◽

The Impact

AbstractChanges in runoff trends have caused severe water shortages and ecological problems in agriculture and human well-being in Nigeria. Understanding the long-term (inter-annual to decadal) variations of water availability in river basins is paramount for water resources management and climate change adaptation. Climate change in Northern Nigeria could lead to change of the hydrological cycle and water availability. Moreover, the linkage between climatic changes and streamflow fluctuations is poorly documented in this area. Therefore, this study examined temporal trends in rainfall, temperature and runoff records of Kaduna River basin. Using appropriate statistical tools and participatory survey, trends in streamflow and their linkages with the climate indices were explored to determine their amplifying impacts on water availability and impacts on livelihoods downstream the basin. Analysis indicate variable rainfall trend with significant wet and dry periods. Unlike rainfall, temperature showed annual and seasonal scale statistically increasing trend. Runoff exhibit increasing tendency but only statistically significant on annual scale as investigated with Mann–Kendall trend test. Sen’s estimator values stood in agreement with Mann–Kendall test for all variables. Kendall tau and partial correlation results revealed the influence of climatic variables on runoff. Based on the survey, some of the hydrological implications and current water stress conditions of these fluctuations for the downstream inhabitants were itemized. With increasing risk of climate change and demand for water, we therefore recommend developing adaptive measures in seasonal regime of water availability and future work on modelling of the diverse hydrological characteristics of the entire basin.

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Inconsistency of Global Vegetation Dynamics Driven by Climate Change: Evidences from Spatial Regression

Remote Sensing ◽

10.3390/rs13173442 ◽

2021 ◽

Vol 13 (17) ◽

pp. 3442

Author(s):

Dou Zhang ◽

Xiaolei Geng ◽

Wanxu Chen ◽

Lei Fang ◽

Rui Yao ◽

...

Keyword(s):

Climate Change ◽

Vegetation Index ◽

Climatic Factors ◽

Potential Evapotranspiration ◽

Anthropogenic Activities ◽

Test Method ◽

Spatial Error ◽

Vegetation Growth ◽

Annual Peak ◽

Global Vegetation

Global greening over the past 30 years since 1980s has been confirmed by numerous studies. However, a single-dimensional indicator and non-spatial modelling approaches might exacerbate uncertainties in our understanding of global change. Thus, comprehensive monitoring for vegetation’s various properties and spatially explicit models are required. In this study, we used the newest enhanced vegetation index (EVI) products of Moderate Resolution Imaging Spectroradiometer (MODIS) Collection 6 to detect the inconsistency trend of annual peak and average global vegetation growth using the Mann–Kendall test method. We explored the climatic factors that affect vegetation growth change from 2001 to 2018 using the spatial lag model (SLM), spatial error model (SEM) and geographically weighted regression model (GWR). The results showed that EVImax and EVImean in global vegetated areas consistently showed linear increasing trends during 2001–2018, with the global averaged trend of 0.0022 yr−1 (p < 0.05) and 0.0030 yr−1 (p < 0.05). Greening mainly occurred in the croplands and forests of China, India, North America and Europe, while browning was almost in the grasslands of Brazil and Africa (18.16% vs. 3.08% and 40.73% vs. 2.45%). In addition, 32.47% of the global vegetated area experienced inconsistent trends in EVImax and EVImean. Overall, precipitation and mean temperature had positive impacts on vegetation variation, while potential evapotranspiration and vapour pressure had negative impacts. The GWR revealed that the responses of EVI to climate change were inconsistent in an arid or humid area, in cropland or grassland. Climate change could affect vegetation characteristics by changing plant phenology, consequently rendering the inconsistency between peak and mean greening. In addition, anthropogenic activities, including land cover change and land use management, also could lead to the differences between annual peak and mean vegetation variations.

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Spatial and Temporal Variations of Potential Evapotranspiration in the Loess Plateau of China During 1960–2017

Sustainability ◽

10.3390/su12010354 ◽

2020 ◽

Vol 12 (1) ◽

pp. 354 ◽

Cited By ~ 1

Author(s):

Congjian Sun ◽

Zhenjing Zheng ◽

Wei Chen ◽

Yuyang Wang

Keyword(s):

Climate Change ◽

Loess Plateau ◽

Hydrological Cycle ◽

Climatic Factors ◽

Potential Evapotranspiration ◽

Southern Oscillation ◽

Chinese Loess Plateau ◽

Future Climate Change ◽

Strong Positive Correlation ◽

The Loess Plateau

Potential evapotranspiration (ET0) is an integral component of the hydrological cycle and the global energy balance, and its long-term variation is of much concern in climate change studies. The Loess Plateau is an important area of agricultural civilization and water resources research. This study analyzed the spatial and temporal evolution processes and influential parameters of ET0 at 70 stations in different topographical areas of the Chinese Loess Plateau (CLP). Using the Mann–Kendall trend, Cross wavelet transform, and the ArcGIS platform, the ET0 of each station was quantified using the Penman–Monteith equation, and the effects of climatic factors on ET0 were assessed by analyzing the correlation coefficients and contribution rates of the climatic factors. The results showed that: (1) the overall trend of the ET0 in different terrains of the Loess Plateau is consistent, however, the ET0 values differ; the hill region (HR) has the highest ET0, followed by the valley region (VR), and the mountain region (MR) has the lowest, and ET0 changes differ between seasons. (2) Spatial distribution characteristics of multiyear mean ET0 in the study are as follows: the ET0 values in mountain and hilly areas are decreasing from west to east, and the higher mean annual ET0 value in the VR is mainly concentrated in the eastern CLP. (3) In the past 58 years, the annual mean and the seasonal ET0 of the region showed increasing trends, however, differences in different terrains were obvious. (4) ET0 has significant correlations with El Niño–Southern Oscillation (ENSO), Pacific–North American teleconnection (PNA), and Atlantic Multidecadal Oscillation (AMO). The resonance period of ET0 and ENSO was 3–6 a, mainly in 1976–1985. The mean coherence phase angle was close to 360°, indicating that ET0 lags behind PNA by approximately 2–6 a; ET0 has a very strong positive correlation with AMO. (5) Relative humidity (RH) is the main influencing factor of ET0 change in the Loess Plateau. Temperature (T) variation has the highest contribution rate (42%) to the regional ET0 variation in the entire CLP. We should pay more attention to the variation of evaporation under future climate change, especially temperature change.

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Impacts of Climate and Anthropogenic Activities on Streamflow Regimes in the Beiluo River, China

Water ◽

10.3390/w13202892 ◽

2021 ◽

Vol 13 (20) ◽

pp. 2892

Author(s):

Zhibo Xie ◽

Xingmin Mu ◽

Peng Gao ◽

Changxue Wu ◽

Dexun Qiu

Keyword(s):

Climate Change ◽

Water Resources ◽

Human Activities ◽

Potential Evapotranspiration ◽

Anthropogenic Activities ◽

Annual Streamflow ◽

Impact Of Climate Change ◽

Daily Streamflow ◽

Significant Downward Trend ◽

The Impact

Quantitatively assessing the characteristics of river streamflow variation and conducting research on attribution identification are the basis for formulating climate-change response strategies and rational use of water resources. Based on the daily streamflow data of the Zhuangtou Hydrological Station in 1970–2018, this paper analyzes the streamflow changes in the Beiluo River Basin and studies the impact of climate change and anthropogenic activities on the streamflow in this basin. A non-parametric Mann–Kendall test and Pettitt’s test were used to determine the trend and detect abrupt changes of streamflow and baseflow. The method based on precipitation and potential evapotranspiration, as well as the double-mass curve of precipitation–streamflow, was established to evaluate the impact of climate change and non-climate factors on annual streamflow. The results reveal a statistically significant downward trend (p = 0.01) in both annual streamflow and baseflow, with the abrupt point year in 1994 and 1988, respectively. When comparing to a modest declining trend in annual average precipitation, we see that the temperature showed a significant upward trend (p = 0.01), whose abrupt point year was 1996. Under the policy of returning farmland to forest, land-use analysis shows that the area of farmland had decreased by 222.4 km2, of which 31.4% was mainly converted into the forestland. By the end of 2015, the area of forestland had increased by 123.4 km2, which has largely caused streamflow decrease. For the method based on precipitation and potential evapotranspiration, climate change contributed 43.7% of the annual streamflow change, and human activities (mainly refers to LUCC) contributed 56.3%. For the DMC of precipitation–streamflow, the precipitation contributed 9.4%, and non-precipitation factors (mainly refers to human activities) contributed 90.6%, and human activities played a more vital part in driving streamflow reduction in different decades, with a contribution rate of more than 70%. This study is of great practical significance to the planning, management, development and utilization of water resources in basins.

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Decomposition and Attribution Analysis of Runoff Alteration of the Dongting Lake in China

Water ◽

10.3390/w12102729 ◽

2020 ◽

Vol 12 (10) ◽

pp. 2729

Author(s):

Yuyun Huang ◽

Minghui Yu ◽

Haoyong Tian ◽

Yujiao Liu

Keyword(s):

Climate Change ◽

Sensitivity Analysis ◽

Human Activities ◽

Potential Evapotranspiration ◽

Dominant Role ◽

Meteorological Data ◽

Dongting Lake ◽

Change Points ◽

Runoff Change ◽

Runoff Depth

The runoff process in the Dongting Lake has been influenced by climate change and human activities in recent decades. To manage the Dongting Lake efficiently and exploit water resources properly under the background of water shortage, it is desired to detect the factors of runoff change in the Dongting Lake. Hydro-meteorological data from 1961 to 2019 are analyzed to reveal the climate change and runoff alteration of the Dongting Lake comprehensively. Mutation test is used to detect the change points of runoff depth series, finding that 1984 and 2005 are change points and therefore 1961–1983, 1984–2004, and 2005–2019 are regarded as baseline period (BP), period 1 (P1), and period 2 (P2), respectively. Eight methods are used to quantitatively assess the relative contribution of human activities and climate change on runoff variation. It reveals that climate change especially precipitation change plays the dominant role (climate change makes runoff depth increase 70.14–121.51 mm, human activities make runoff depth decrease 51.98–103.35 mm) in runoff alteration in P1 while human activities play a prime role (account for 88.47–93.17%) in P2. Human activities such as reservoir construction, water consumption, and land-use (land-cover) change may be the main factors that influence the runoff in the Dongting Lake in P2. According to the sensitivity analysis, runoff in the Dongting Lake is more sensitive to climate change in P2 compared with that in P1, and no matter in P1 or P2, runoff is more sensitive to change in precipitation than the change in potential evapotranspiration. Combined with climate forecast, the results of sensitivity analysis can be used to estimate runoff change caused by climate change in the future.

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

Scientific Data ◽

10.1038/s41597-021-01003-9 ◽

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.

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

International Journal of Environmental Research and Public Health ◽

10.3390/ijerph16142506 ◽

2019 ◽

Vol 16 (14) ◽

pp. 2506 ◽

Cited By ~ 3

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.

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An Improved Conceptual Model Quantifying the Effect of Climate Change and Anthropogenic Activities on Vegetation Change in Arid Regions

Remote Sensing ◽

10.3390/rs11182110 ◽

2019 ◽

Vol 11 (18) ◽

pp. 2110

Author(s):

Yu ◽

Yang ◽

Li ◽

Yang

Keyword(s):

Climate Change ◽

Conceptual Model ◽

Arid Regions ◽

Vegetation Change ◽

Hydrological Cycle ◽

Anthropogenic Activities ◽

Regional Scale ◽

Anthropogenic Activity ◽

Area Index ◽

The Impact

Vegetation shows a greening trend on the global scale in the past decades, which has an important effect on the hydrological cycle, and thus quantitative interpretation of the causes for vegetation change is of great benefit to understanding changes in ecology, climate, and hydrology. Although the Donohue13 model, a simple conceptual model based on gas exchange theory, provides an effective tool to interpret the greening trend, it cannot be used to evaluate the impact from land use and land cover change (LULCC) on the regional scale, whose importance to vegetation change has been demonstrated in a large number of studies. Hence, we have improved the Donohue13 model by taking into account the change in vegetation cover ratio due to LULCC, and applied this model to the Yarkand Oasis in the arid region of northwest China. The estimated change trend in leaf area index (LAI) is 1.20%/year from 2001 to 2017, which accounts for approximately half of the observed (2.31%/year) by the moderate resolution imaging spectroradiometer (MODIS). Regarding the causes for vegetation greening, the contributions of: (1) LULCC; (2) atmospheric CO2 concentration; and (3) vapor pressure deficit were: (1) 88.3%; (2) 40.0%; and (3) −28.3%, respectively, which reveals that the largest contribution was from LULCC, which is probably driven by increased total water availability in whole oasis with a constant transpiration in vegetation area. The improved Donohue13 model, a simple but physics-based model, can partially explain the impact of factors related to climate change and anthropogenic activity on vegetation change in arid regions. It can be further combined with the Budyko hypothesis to establish a framework for quantifying the changes in coupled response of vegetation and hydrological processes to environment changes.

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Response of grassland productivity to climate change and anthropogenic activities in arid regions of Central Asia

PeerJ ◽

10.7717/peerj.9797 ◽

2020 ◽

Vol 8 ◽

pp. e9797

Author(s):

Xu Bi ◽

Bo Li ◽

Lixin Zhang ◽

Bo Nan ◽

Xinshi Zhang ◽

...

Keyword(s):

Climate Change ◽

Central Asia ◽

Human Activity ◽

Arid Regions ◽

Net Primary Production ◽

Anthropogenic Activities ◽

Grazing Pressure ◽

Anthropogenic Activity ◽

Grassland Degradation ◽

Basin System

Background Quantitative evaluations of the relative impacts of climate change and anthropogenic activity on grasslands are significant for understanding grassland degradation mechanisms and controlling degraded grasslands. However, our knowledge about the effects of anthropogenic activities and climate change on the grassland in a mountain basin system in arid regions of Central Asia is still subject to great uncertainties. Methods In this research, we have chosen the net primary productivity (NPP) as an index for revealing grassland dynamics processes. Moreover, the human appropriation of net primary production (NPPH), which was calculated as the potential NPP (NPPP) minus the actual NPP (NPPA), was applied to distinguish the relative influences of climate change and human activities on the grassland NPP variations in a mountain basin system of Central Asia from 2001–2015. Results The results indicated that the grassland NPPA showed an increasing trend (35.88%) that was smaller than the decreasing trend (64.12%). The respective contributions of human activity, climate change and the two together to the increase in the NPPA were 6.19%, 81.30% and 12.51%, respectively. Human activity was largely responsible for the decrease in the grassland NPPA, with the area experiencing human-induced decreases accounting for 98.21% of the total decreased area, which mainly occurred during spring/autumn pasture and winter pasture. Furthermore, the average grazing pressure index (GPI) values of summer pastures, spring/autumn pasture and winter pastures were 1.04, 3.03 and 1.83, respectively, from 2001–2015. In addition, negative correlations between the NPP and GPI occupied most of the research area (92.41%). Discussion Our results indicate that: (i) anthropogenic activities were the primary cause of the reduction in the grassland NPP, especially grazing activities. (ii) For areas where the grassland NPP has increased, precipitation was the dominant climatic factor over temperature in controlling the grassland NPP changes in the study area. (iii) The findings of the current research indicate that some measures should be taken to reduce livestock pressure, and artificial grasslands can be built along the Irtysh River and the Ulungur River to relieve grazing pressure on spring/autumn pastures and winter pastures. Our results could provide reliable information for grassland management and the prevention of grassland degradation in arid regions of Central Asia.

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