Understanding the impacts of climate change and human activities on hydrological processes, especially the baseflow, is vital for sustainable water resource management. We analyzed the global changes ...in baseflow and baseflow index (BFI) for 2,374 global streamflow stations from 1970 to 2016 to examine their associations with precipitation, temperature, terrestrial water storage (TWS), normalized difference vegetation index (NDVI) representing the vegetation regimes, potential evapotranspiration (PET), and a humidity index (HI)‐precipitation/PET. Results showed that changes in both baseflow and BFI are significantly region dependent in continents, due to spatial differences of changes in climate and vegetation that determines the baseflow generation. Seasonal baseflow changed slightly, while seasonal BFI varied greatly, partly due to the shift from snowfall to rainfall and warming effects on glacial retreat and the timing of snowmelt. The multibasin baseflow elasticity analyses show that baseflow (BFI) was highly sensitive to changes in NDVI, precipitation, and temperature (temperature and PET). The multivariate regression analyses show that globally, changes in precipitation and TWS contributed to the majority (64.8% and 20.2%) of changes in baseflow, while changes in HI, PET, and precipitation contributed to the majority (30.3%, 28.9%, and 27.5%) of changes in BFI. The spatially varying interaction between climate, vegetation, and baseflow implies that regional adaptation of water resources utilization to climate change should consider the regional shifts in vegetation. This study quantified the elasticity and relative contribution of changes in geographic factors to changes in baseflow and BFI around the world and could inform practices for sustainable water management.
Key Points
Impacts of changes in terrestrial water storage, normalized difference vegetation index, temperature, precipitation, potential evapotranspiration, and humidity index on changes in baseflow are assessed
Changes in baseflow and its index are significantly region dependent in continents due to differences of changes in climate and vegetation
Baseflow changes are most sensitive to changes in vegetation changes and mainly attributed to changes in precipitation and TWS
Assessing the water budget closures and source of water budget imbalances is fundamental to improving the understanding of changes in the hydrological system and their associated impacts. We analyzed ...the long‐term (1982–2016) water budget for 1,561 watersheds by using various observed data sets for precipitation (P), evapotranspiration (ET), observed streamflow (Q), and total water storage change (∆TWS). The results show that 93%, 79%, 44%, and 20% of watersheds show water imbalances ratio less than 30%, 20%, 10%, and 5% of their corresponding precipitation. The average absolute water imbalance ratio for all watersheds is 14.2% of P. Watersheds showing large water imbalance ratio values are mostly located in biomes of Tropical and Subtropical Moist Broadleaf Forests, Boreal Forests/Taiga, and Tundra. Different P, ET, and Q data set combinations result in different degrees of water imbalance. The water budget imbalance ratio shows a significant negative relationship with humidity index and vegetation coverage, while a positive relationship with the proportions of irrigation area and watershed area. Showing small water imbalances for most watersheds, reanalysis precipitation data set (ERA5 and MSWEP), MTE evapotranspiration data set performed better than other data sets in water budget analyses in most biomes. The uncertainties of P, ET, Q, and ∆TWSGRACE contribute to 40.1%, 14.3%, 26.6%, and 19% of the water budget imbalance on average, respectively. Improving the accuracy of P and ET estimates, and streamflow measurements are critical to better understanding the water budget and improves modeling of hydrological processes.
Key Points
Water budget imbalances are less than 30%, 20%, 10%, and 5% of precipitation for 93%, 79%, 44%, and 20% of all watersheds
Reanalysis precipitation (ERA5 and MSWEP) and MTE evapotranspiration perform better than other data sets in the water budget in most biomes
Moist Broadleaf Forests, Boreal Forests/Taiga, and Tundra show the largest water imbalance ratio due to bias in hydroclimatic data sets
Aims
Since the 1970s, extensive croplands were converted to forest and pasture lands to control severe soil erosion on the Loess Plateau of China. We quantify the direct and indirect effects of ...vegetation restoration on runoff and sediment yield on hillslopes in the field to improve environmental governance.
Methods
An artificial rainfall experiment at a rainfall intensity of 120 mm h
−1
and a slope gradient of 22° were used to distinguish the effects of vegetation restoration on runoff and sediment yield.
Results
Compared to the farmland slopes, vegetation restoration directly prolonged the time-to-runoff by 140%, reduced the runoff rate by 20%, and increased the soil infiltration capacity by 15%. Vegetation restoration indirectly delayed the time-to-runoff by 120%, reduced the runoff rate and sediment yield rate by 50% and 94%, respectively, and increased the soil infiltration capacity by 58% on the hillslopes with vegetation restoration.
Conclusions
The direct effects of vegetation restoration on runoff and sediment yield were lower than its indirect impacts. Vegetation cover, decreases in soil bulk density, and increases in belowground root biomasses and > 0.25 mm aggregate stability were the primary causes of runoff and sediment yield reduction on the slopes with vegetation restoration.
Precipitation whiplash, including abrupt shifts between wet and dry extremes, can cause large adverse impacts on human and natural systems. Here we quantify observed and projected changes in ...characteristics of sub-seasonal precipitation whiplash and investigate the role of individual anthropogenic influences on these changes. Results show that the occurrence frequency of global precipitation whiplash is projected to be 2.56 ± 0.16 times higher than in 1979-2019 by the end of the 21
Century, with increasingly rapid and intense transitions between two extremes. The most dramatic increases of whiplash show in the polar and monsoon regions. Changes in precipitation whiplash show a much higher percentage change than precipitation totals. In historical simulations, anthropogenic greenhouse gas (GHG) and aerosol emissions have increased and decreased precipitation whiplash occurrences, respectively. By 2079, anthropogenic GHGs are projected to increase 55 ± 4% of the occurrences risk of precipitation whiplash, which is driven by shifts in circulation patterns conducive to precipitation extremes.
Snow cover is highly sensitive to global warming, and it, in return, has huge impacts on global and regional climate change. Because of the limitations of in-situ observations, only a few studies ...have analyzed the dynamics of snow cover across the whole of China. In this study, we studied the spatio-temporal variabilities of snow cover over China and explored the covary of snow cover with precipitation and temperature in spring and winter based on the surface snow cover observations of 201 meteorological stations in China during 1960–2013. The temporal and spatial distribution characteristics of the mean daily snow depth and the number of snow cover days were analyzed. Results showed snow depth and the number of snow-cover days were high in Northeast China, Eastern China-Inner Mongolia, Northern Xinjiang, Southeastern and South Region of the Tibetan Plateau. The trend of snow depth and the number of snow-cover days varied among different regions. Snow depth recorded at 34.3% of the stations showed an increasing trend during the study period. There were increasing trends of the snow-cover days at 40.8% of stations. Increasing trends of the mean annual daily snow depth and the number of snow-cover days were statistically insignificant (p > 0.05) while an abrupt change of the number of snow cover days was found in 1975. Change points of the mean daily snow depth in autumn and winter occurred in 1987 and 2008, respectively. Change points of the number of snow-cover days in spring and winter occurred in 2009 and 1983, respectively. Snow cover in China covaried with various climate factors, i.e., precipitation or temperature. This study improved our knowledge on snow cover changes and is beneficial for further studies on climate change in China.
•Spatiotemporal variability of snow-cover over China were investigated.•Almost half of snow gauge stations over China shows increases in the snow-cover days.•Abrupt changes in annual snow cover over China occurred in around 1975.
Purpose
Extensive vegetation recovery has been implemented to control severe soil erosion on the Loess Plateau, China. However, no systematic study has been done on the soil improvement benefit and ...preferable pattern of vegetation rehabilitation. In this study, the effects of vegetation restoration on soil physical properties at ten sites with different vegetation types and varying restoration periods were investigated.
Materials and methods
The experiment was carried out in the Yanhe river basin in the hilly-gully region of the Loess Plateau. Ten sites, including two replanted arboreal forests for 25 and 35 years, three replanted scrubland for 15, 30, and 45 years, four secondary natural grassland for 10, 20, 30, and 40 years, and one farmland, were selected for soil sampling. Sampling was conducted at 0–20 cm and 20–40 cm layers.
Results and discussion
Vegetation restoration significantly decreased bulk density, and increased aggregate stability and saturated hydraulic conductivity (Ks), while their effects on porosity was complicated. The soil texture class did not change with vegetation succession, but minor differences in sand, silt, and clay components were observed. Bulk density, macroporosity, and > 0.25 mm aggregate stability were the principal physical parameters that affected Ks. Moreover, bulk density had the most effect on Ks (− 0.84), while > 0.25 mm aggregate stability had the lowest impact (0.38). Bulk density and Ks were correlated with most of the other soil physical properties. Replanted scrubland and secondary natural grassland had higher soil physical quality index (
S
Dexter
) than replanted arboreal forests and farmland.
Conclusions
It is reasonable to take bulk density and Ks as the indicators to evaluate the effect of vegetation restoration on soil physical properties. Planting shrubs and grassland is better than forest for eco-environment rehabilitation in the study area. Results of this study provide a reference to regional eco-environmental rehabilitation and conservation.
The Dongjiang River Basin (DRB), Southern China.
Quantifying the impacts of climate change on blue water (BW) and green water (GW) resources is important for the efficient management of water ...resources and watersheds socio-economic development. This study projects the impacts of climate change on blue and green water availability in DRB, using the multi-water-flux calibrated soil and water assessment tool (SWAT), the future land use simulation model (Geosos-FLUS), and the outputs of 21 global climate models under two Shared Socioeconomic Pathways (SSP126 and SSP585) that were bias-corrected by utilizing the quantile delta mapping method for the near (2030–2064) and far future (2065–2100).
The results indicate that annual precipitation, temperature, and extreme precipitation are projected to increase in DRB in the future. Future increases in precipitation intensity are projected to result in variations in the partition of precipitation to blue and green water, increases in blue water and green water flow (GWF), and decreases in green water storage (GWS). Climate change is projected to decrease seasonal water availability and exacerbate green water scarcity (GWSC) in DRB. Therefore, it is crucial to consider changes in the precipitation intensity on the regional blue and green water security. Our finding can assist watershed managers in identifying future hydrologic risks and developing appropriate adaptation policies.
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•Multi-water-flux validated SWAT model simulated blue and green water.•Precipitation intensity affects the partition of blue and green water.•Climate change may decrease water availability and intensify green water scarcity.
The Pearl River Basin (PRB), located in the south of China, has a tropical to subtropical climate.
In this study, we present an improved process-based approach to assess the intensity of the Dry-Wet ...Abrupt Alternation (DWAA) events, considering both the transition gap (alternation) and the transition rate (urgency) between dry and wet states. Using daily precipitation data from 1961 to 2020 across 75 meteorological stations in the PRB, we analyze the temporal and spatial evolution patterns of DWAA events.
The findings reveal that: (1) DWAA events in the western region generally occur less frequently but with higher intensity. (2) Dry-to-wet (D-W) events have an urgency intensity of 1.35, almost twice that of wet-to-dry (W-D) events at 0.69. However, the alternation intensity of W-D is only slightly higher by 0.17 compared to D-W. (3) The alternation and urgency changes in D-W events are asynchronous, with alternation intensity initially decreasing from 9.7 to 9.27, then increasing to 9.58, while urgency decreases continuously from 1.66 to 1.07. (4) The alternation and urgency changes in W-D events are synchronous. The alternation intensity initially decreases from 9.7 to 9.06, then rises to 10.1, while the urgency intensity decreases from 0.68 to 0.58 before subsequently climbing to 0.8.
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•Improved process-based approach to assess the intensity of drought-flood abrupt alternation.•Changes of alternation and urgency in drought-to-flood events are not synchronized.•Drought-flood abrupt alternation show a pattern of "east is more, west is stronger".
•Responses of streamflow to changes in vegetation composition and climate variability were investigated considering changes in the terrestrial water storage.•The Budyko parameter is significantly ...related to vegetation composition and climate variability.•Streamflow changes were more (less) sensitive to tree coverage than non-tree coverage in humid (arid) regions.
Vegetation and climate play critical roles in the hydrological cycle as vital components of the earth system. Understanding the impacts of changes in vegetation composition and climate on hydrological processes is essential for water balance and sustainable water resource management. We analyzed the effects of changes in vegetation composition and climate variability on streamflow changes in 3434 global watersheds from 2003 to 2016 using the Budyko framework. We found that ignoring changes in terrestrial water storage would result in large errors in the influence of landscape changes on streamflow changes. The sensitivity of streamflow changes to climate seasonality index (CSI), precipitation seasonality index (PSI), total vegetation coverage (M), tree coverage (MT), and non-tree coverage (MNT) varied in different regions. Effective precipitation (Pe), potential evapotranspiration (PET), CSI, PSI, M, MT, and MNT changes were the dominant factor in streamflow changes for 64.8%, 3.0%, 5.1%, 4.1%, 9.8%, 7.7%, 5.6% of global watersheds, respectively. Attributing streamflow changes showed that the effects of MT and MNT on streamflow changes were mutually reinforcing in most basins. The influence of vegetation composition on streamflow changes was greater in semi-humid and arid regions than in humid regions. This research quantified the impacts of vegetation composition changes and climate change on streamflow changes worldwide and could clarify the hydrological responses to changing environments.
