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Solar-induced chlorophyll fluorescence (SIF) has been used since its discovery to characterize vegetation photosynthesis and is an effective tool for monitoring vegetation dynamics. Its response to meteorological drought enhances our comprehension of the ecological consequences and adaptive mechanisms of plants facing water scarcity, informing more efficient resource management and efforts in mitigating climate change. This study investigates the spatial and temporal patterns of SIF and examines how vegetation SIF in the Yellow River Basin (YRB) responds to meteorological drought. The findings reveal a gradual southeast-to-northwest decline in SIF across the Yellow River Basin, with an overall increase-from 0.1083 W m -2 μm -1 sr -1 in 2001 to 0.1468 W m -2 μm -1 sr -1 in 2019. Approximately 96% of the YRB manifests an upward SIF trend, with 75% of these areas reaching statistical significance. The Standardized Precipitation Evapotranspiration Index (SPEI) at a time scale of 4 months (The SPEI-4), based on the Liang-Kleeman information flow method, is identified as the most suitable drought index, adeptly characterizing the causal relationship influencing SIF variations. As drought intensified, the SPEI-4 index markedly deviated from the baseline, resulting in a decrease in SIF values to their lowest value; subsequently, as drought lessened, it gravitated towards the baseline, and SIF values began to gradually increase, eventually recovering to near their annual maximum. The key finding is that the variability of SIF with SPEI is relatively pronounced in the early growing season, with forests demonstrating superior resilience compared to grasslands and croplands. The responsiveness of vegetation SIF to SPEI can facilitate the establishment of effective drought early warning systems and promote the rational planning of water resources, thereby mitigating the impacts of climate change., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

The sediment load on the Chinese Loess Plateau has sharply decreased in recent years. However, the contribution of terrace construction and vegetation restoration projects to sediment discharge reduction remains uncertain. In this paper, eight catchments located in the Loess Plateau were chosen to explore the effects of different driving factors on sediment discharge changes during the period from the 1960s to 2012. Attribution approaches were applied to evaluate the effects of climate, terrace, and vegetation coverage changes on sediment discharge. The results showed that the annual sediment discharge decreased significantly in all catchments ranging from -0.007 to -0.039 Gt·yr -1 . Sediment discharge in most tributaries has shown abrupt changes since 1996, and the total sediment discharge was reduced by 60.1% during 1997-2012. We determined that increasing vegetation coverage was the primary factor driving the reductions in sediment loads since 1996 and accounted for 47.7% of the total reduction. Climate variability and terrace construction accounted for 9.1% and 18.6% of sediment discharge reductions, respectively., (Copyright © 2018. Published by Elsevier B.V.)

Water conservation is an important ecosystem service, which is crucial to the fragile ecological environment and serious soil erosion in Northwest China. However, water conservation has been affected by climate change and human disturbance, and its future spatial and temporal changes are still unclear. This study employed the Integrated Valuation of Ecosystem Services and Trade‐offs (InVEST) model to assess the water conservation capacity of Northwest China between 1990 and 2020. Subsequently, the Patch‐generating Land Use Simulation (PLUS) model and the NASA Earth Exchange Global Daily Downscaled Projections (NEX‐GDDP‐CMIP6) were integrated to examine changes in water conservation from 2030 to 2050. The water conservation quantity in Northwest China had a fluctuating growth tendency between 1990 and 2020, with an average of 816.61 × 108 m3. The water conservation capacity's regional distribution pattern shows a steady increase from northwest to southeast. Northwest China's forest land had the greatest water conservation capacity between 1990 and 2020, at 66 mm, while the water land had the lowest, at 1.46 mm. The water conservation capacity in the 2030–2050 future scenario is less than that in 2020 when the regional distribution pattern is comparable to 2020. Natural development scenario (ND) in 2030 has the lowest water conservation capacity (13.41 mm) under ssp1‐2.6 precipitation scenario, whereas in 2050, the highest water conservation capacity (17.47 mm) is found in same scenario. The ecological protection scenario (EP) has the greatest water retention capacity (18.15 mm in 2040) and the lowest (14.38 mm in 2050) in the ssp5‐8.5 scenario. Our research can help restore and rebuild Northwest China's natural ecosystem and offer a theoretical foundation for the protection of ecological environment and the rational utilization of water resources in the region. [ABSTRACT FROM AUTHOR]

Over the past three decades, there has been a significant global climate change characterized by an increase in the intensity and frequency of extreme climate events. The vegetation status in Qinghai Province has undergone substantial changes, which are more pronounced than other regions in the Qinghai-Tibet Plateau. However, a clear understanding of the response characteristics of plateau vegetation to extreme climate events is currently lacking. In this study, we investigated the response of net primary productivity (NPP) to different forms of extreme climate events across regions characterized by varying levels of aridity and elevation gradients. Specifically, we observed a significant increase in NPP in relatively arid regions. Our findings indicate that, in relatively arid regions, single episodes of high-intensity precipitation have a pronounced positive effect (higher correlation) on NPP. Furthermore, in high-elevation regions (4000–6000 m), both the intensity and frequency of precipitation events are crucial factors for the increase in regional NPP. However, continuous precipitation can have significant negative impacts on certain areas within relatively wet regions. Regarding temperature, a reduction in the number of frost days within a year has been shown to lead to a significant increase in NPP in arid regions. This reduction allows vegetation growth rate to increase in regions where it was limited by low temperatures. Vegetation conditions in drought-poor regions are expected to continue to improve as extreme precipitation intensifies and extreme low-temperature events decrease. [ABSTRACT FROM AUTHOR]

Understanding the impact of climate change and human activities on runoff is crucial for water resources management. However, an evaluation of available methods for analysing this impact is lacking. In this study, we comprehensively reviewed four commonly used quantitative methods: the Soil and Water Assessment Tool (SWAT) model, Budyko-based approach, and two empirical methods, i.e., Double mass curve (DMC) and Modified DMC (MDMC). Using the Wei River basin as a case study, we assessed the runoff reduction influenced by climate change and human activities from 1970 to 2017. The results show that human activities are the primary driver for runoff reduction. The highest contribution of human activities was estimated by the DMC (93.2%–99.9%), followed by MDMC and SWAT (65.6%–87.1%), while the Budyko-based had the smallest estimates (55.3%–61.2%). Each method has advantages and limitations, so the appropriate method should be selected based on research objectives and data availability/quality. [ABSTRACT FROM AUTHOR]

Runoff and sediment discharge have displayed great reductions due to climate change and enhanced various human activities during recent decades in the Jialing River, China, with significant environmental and social implications. The water balance equation, double mass curve, and linear regression analysis were employed to quantify the contributions of climate change and human activities to runoff and sediment discharge reductions in the Jialing River during 1960–2017. The results indicated that the annual runoff of the Jialing River exhibited a significant decreasing trend of − 2.75 × 108 m3 every year (P < 0.05) but no significant abrupt change occurred, while annual sediment discharge significantly decreased by 0.03 × 108 t every year (P < 0.05) with a significant abrupt change in 1990 (P < 0.05). Climate change led to a great reduction (82.2%) in annual runoff from 1960 to 2017 in the Jialing River, whereas the contribution of climate change to sediment discharge reduction in the human-affected period (1990–2017) was only 4.55% and precipitation inclined to increase sediment discharge in recent years (2010–2017). The reduced sediment discharge in the 1990s was mostly due to the implementation of soil–water conservation programs and the reduction after 2000 was due to the development of reservoirs as well as the implementation of soil–water conservation programs. The results provided references to develop various human activities better and drew great attention to strengthening basin management. [ABSTRACT FROM AUTHOR]

A rapid reduction in run‐off has been observed in the middle reaches of the Yellow River basin in recent decades. Understanding the contributions of climate change and human activities, such as vegetation restoration and water consumption, to surface water resource reduction has become urgent and very important for future regional planning. Here, we use attribution approaches to explore the effects of climate change and human activities on run‐off over the past six decades. The results showed that the observed annual run‐off at Tongguan station, which is located within the mainstream of the Yellow River, exhibited a significant decreasing trend of −0.69 mm year−1 (p <.01) and varied from −0.28 to −1.46 mm year−1 (p <.01) in the eight selected tributaries from 1960 to 2015. Two relatively abrupt changes in the double mass curves occurred around 1979 and 1999; compared with Period 1 (P1; 1960–1979), the average catchment run‐off decreased 32% during Period 2 (P2; 1980–1999) and up to 49% during Period 3 (P3; 2000–2015). We calculated that approximately 29% of the reduction in the run‐off during P2 and 18% during P3 were attributed to climate change. Increased surface water consumption resulted in effective run‐off reduction, with relative contributions of approximately 27% and 28% during P2 and P3, respectively. With the implementation of the "Grain‐for‐Green" project, the vegetation coverage rapidly increased from 36% in P1 to 52% in P3 and reduced run‐off by 35% during P3. These findings explain the run‐off reduction and benefit water resource management in the middle reaches of the Yellow River basin. [ABSTRACT FROM AUTHOR]

Hydrological regimes in the Yellow River have changed significantly because of climate change and intensive human interventions. These changes present severe challenges to water resource utilization and ecological development. Variation of run‐off, suspended sediment load (SSL), and eight precipitation indices (P1: 0–12 mm·day−1, P12: 12–25 mm·day−1, P25: 25–50 mm·day−1, P50: P ≥ 50 mm·day−1 and corresponding rainfall day: Pd1, Pd12, Pd25, Pd50 day year−1) in three critical parts of the Yellow River basin (source region: SRYRB, upper reaches: URYRB, middle reaches: MRYRB) were investigated for the period from 1960 to 2015. The results show that run‐off and SSL significantly decreased (P < 0.01) in the URYRB and the MRYRB, whereas their decline in the SRYRB was insignificant (P > 0.05). Moreover, run‐off in the URYRB had one change point in 1987, and SSL in the URYRB as well as run‐off and SSL in the MRYRB had two change points (in the 1970s and the 1990s). Over the same period, only Pd1 and Pd12 in the SRYRB showed significant increasing trends, and an abrupt change appeared in 1981. The optimal precipitation indices for assessing the effects of precipitation on run‐off and SSL in the URYRB and MRYRB were Pd50 and P12, respectively. A double‐mass curve analysis showed that precipitation and human activities contributed to approximately 20% and 80% of the reduction in run‐off, respectively, for both the SRYRB and the MRYRB. However, the contribution rate of precipitation and human activities on SSL reduction was approximately 40% and 60% in the URYRB and 5% and 95% in the MRYRB, respectively. Human activities, primarily soil and water conservation measures and water extraction (diversion), were the main factors (>50%) that reduced the run‐off. However, the dominant driving factors for SSL reduction were soil and water conservation measures and reservoir interception, for which the contribution rate was higher than 70% in the MRYRB. This work strengthens the understanding of hydrological responses to precipitation change and provides a useful reference for regional water resource utilization. [ABSTRACT FROM AUTHOR]

Environmental change resulting from intensified human interventions and climate change has impacted the hydrological function of many large river systems, largely altering the production and transport of run-off and sediment. It is thus vital to quantitatively evaluate the influence of climate change and human activities on streamflow and sediment discharge. Water balance equations, hydrological models, and comparative analyses are commonly used to fulfil this need. Double mass curves (DMCs), being one useful method for comparative analyses, are characterized by low data requirements and high transferability, and thus more practical than water balance equations and hydrological models for hydrologic benefit evaluations. However, the detailed derivation procedure of the DMC has, to date, yet been described in literature. Moreover, in previous studies, changing points of the DMC were determined either rather empirically or as the changing point of streamflow or sediment discharge (i.e., precipitation was not considered). Hence, the changing point detected may be subject to inaccuracies. This paper, for the first time, comprehensively detailed the derivation procedure of the DMC; a new way was proposed to quantitatively examine the changing point of the DMC; an example was also given to demonstrate the use of the DMC in the hydrologic benefit evaluation. It is hopeful that the method given in our paper will be widely adopted by future studies as a standard procedure to derive and use the DMC. [ABSTRACT FROM AUTHOR]

The nonparametric Mann-Kendall test and the Pettitt test were employed to examine the change trends and shifts of runoff and sediment input to Poyang Lake between 1961 and 2013. Water balance and linear regression models were used to evaluate the impacts of climate variability and human activities on the runoff and sediment discharge changes. The results showed that runoff inputs to the lake had insignificant temporal trends and change points, while sediment inputs had significant decreasing trends, with an abrupt change in 1989. Quantitative assessment demonstrated that human activities led to a small decrease (5.5%) in runoff inputs to the lake, and a dramatic (121.4%) decrease in sediment inputs to the lake between the reference period (before the change point) and the human-influenced period (after the change point). This work provides a useful reference for future policy makers in water resource utilization and environmental safety of the Poyang Lake basin. [ABSTRACT FROM PUBLISHER]

In recent decades, extreme climatic events have been a major issue worldwide. Regional assessments on various climates and geographic regions are needed for understanding uncertainties in extreme events' responses to global warming. The objective of this study was to assess the annual and decadal trends in 12 extreme temperature and 10 extreme precipitation indices in terms of intensity, frequency, and duration over the Loess Plateau during 1960–2013. The results indicated that the regionally averaged trends in temperature extremes were consistent with global warming. The occurrence of warm extremes, including summer days (SU), tropical nights (TR), warm days (TX90), and nights (TN90) and a warm spell duration indicator (WSDI), increased by 2.76 ( P < 0.01), 1.24 ( P < 0.01), 2.60 ( P = 0.0003), 3.41 ( P < 0.01), and 0.68 ( P = 0.0041) days/decade during the period of 1960–2013, particularly, sharp increases in these indices occurred in 1985–2000. Over the same period, the occurrence of cold extremes, including frost days (FD), ice days (ID), cold days (TX10) and nights (TN10), and a cold spell duration indicator (CSDI) exhibited decreases of − 3.22 ( P < 0.01), − 2.21 ( P = 0.0028), − 2.71 ( P = 0.0028), − 4.31 ( P < 0.01), and − 0.69 ( P = 0.0951) days/decade, respectively. Moreover, extreme warm events in most regions tended to increase while cold indices tended to decrease in the Loess Plateau, but the trend magnitudes of cold extremes were greater than those of warm extremes. The growing season (GSL) in the Loess Plateau was lengthened at a rate of 3.16 days/decade ( P < 0.01). Diurnal temperature range (DTR) declined at a rate of − 0.06 °C /decade ( P = 0.0931). Regarding the precipitation indices, the annual total precipitation (PRCPTOT) showed no obvious trends ( P = 0.7828). The regionally averaged daily rainfall intensity (SDII) exhibited significant decreases (− 0.14 mm/day/decade, P = 0.0158), whereas consecutive dry days (CDD) significantly increased (1.96 days/decade, P = 0.0001) during 1960–2013. Most of stations with significant changes in SDII and CDD occurred in central and southeastern Loess Plateau. However, the changes in days of erosive rainfall, heavy rain, rainstorm, maximum 5-day precipitation, and very-wet-day and extremely wet-day precipitation were not significant. Large-scale atmospheric circulation indices, such as the Western Pacific Subtropical High Intensity Index (WPSHII) and Arctic Oscillation (AO), strongly influences warm/cold extremes and contributes significantly to climate changes in the Loess Plateau. The enhanced geopotential height over the Eurasian continent and increase in water vapor divergence in the rainy season have contributed to the changes of the rapid warming and consecutive drying in the Loess Plateau. [ABSTRACT FROM AUTHOR]

Vegetation is an important component of terrestrial ecosystems, and it plays an important role in preventing desertification and conserving soil and water in arid and semi-arid regions. This study examined the spatial distribution and temporal variations of vegetation cover in the Loess Plateau over the last three decades using a time series of the normalized difference vegetation index (NDVI) derived from the long-term data record (LTDR) and the moderate resolution imaging spectroradiometer (MODIS) between 1981 and 2010, along with daily climate datasets. Furthermore, we assessed the relationships between the vegetation, climate variables (i.e., temperature and precipitation), and human activities, particularly the “Grain to Green” restoration program. The greenness of the vegetation cover in the Loess Plateau exhibited a significant increase from the northwest to the southeast. Generally, the NDVI exhibited an increase of 0.0015 year −1 ( P < 0.01) from 1981 to 2010 over the entire plateau, and the rate was particularly high over the last decade. The NDVI increases with a rate of more than 0.01 year −1 during 1991–2000 were distributed throughout the Ziwuling and Huanglongshan Forests in Yan’an, Shaanxi Province, and in the Lvliang and Taihang Mountains, Shanxi Province. However, the distinct feature of the NDVI, namely, its increase of more than 0.01 year −1 in 2001–2010, was associated with key areas of ecological restoration in Yulin and Yan’an in Shaanxi Province. The vegetation cover was largely improved within the last decade due to the “Grain to Green” program. However, revegetation still has great potential in the Huangfuchuan, Kuyehe, Wudinghe, and Yanhe watersheds in the future. In response to global warming, the phenology timing in the Loess Plateau was 3.9 days (1991–2000) and 6.6 days (2001–2010) earlier in spring compared with 1981–1990, and the end of the fall growing season was delayed 3.6 days and 9.6 days, respectively, over the past three decades. The significant and positive partial correlations ( R > 0.5, P < 0.05) between the temperature and the NDVI occurred in the central and southeastern parts of the plateau; this finding indicates that higher temperatures promote the growth of vegetation in less water-stressed areas. However, a negative impact of vegetation degradation due to climate warming was found in the northwestern Loess Plateau. The permafrost slowly degraded in the northwestern Loess Plateau, causing a decrease in the water content of the topsoil, eventually leading to the adverse effects on vegetation. [ABSTRACT FROM AUTHOR]

The carbon and water cycles of terrestrial ecosystems, which are strongly coupled via water use efficiency (WUE), are influenced by global climate change. To explore the relationship between the carbon and water cycles and predict the effect of climate change on terrestrial ecosystems, it is necessary to study the WUE in global terrestrial ecosystems. In this study, the 13-year WUE (i.e., net primary production (NPP)/evapotranspiration (ET)) of global terrestrial ecosystems was calculated based on the Moderate Resolution Imaging Spectro-radiometer (MODIS) NPP (MOD17A3) and ET (MOD16A3) products from 2000 to 2012. The results indicate that the annual average WUE decreased but not significantly, and the 13-year mean value was 868.88 mg C m mm . The variation trend of WUE value for each pixel differed greatly across the terrestrial ecosystems. A significant variation ( P<0.05) occurred in about 18.50% of the land surface. WUE was spatially distributed from 0 to 2541 mg C m mm , and 58.78% of the WUE values were concentrated in the interval of 600-1200 mg C m mm . The WUE increased from north to south in Africa and Oceania and from east to west in Europe and South America. Both latitudinal and longitudinal gradients existed in Asia and North America. The following trends in the WUE of different continents and Köppen-Geiger climates were observed: Europe (1129.71 mg C m mm )> Oceania (1084.46 mg C m mm )> Africa (893.51 mg C m mm )> South America (893.07 mg C m mm )> North America (870.79 mg C m mm )> Asia (738.98 mg C m mm ) and warm temperate climates (1094 mg C m mm )> snowy climates (862 mg C m mm )> arid climates (785 mg C m mm )> equatorial climates (732 mg C m mm )> polar climates (435 mg C m mm ). Based on the WUE value and the present or future rainfall, the maximum carbon that fixed in one region may be theoretically calculated. Also, under the background of global climatic change, WUE may be regarded as an important reference for allotting CO emissions offsets and carbon transactions. [ABSTRACT FROM AUTHOR]

• Noticeable streamflow increased during the period of underground mining. • Streamflow greatly reduced when open cut mining was largely expanded. • Increased streamflow is likely due to over-pumping to sustain the underground mining. • Large uncertainty in coal mining contribution existed among the different approaches. Exploring the impacts of mining-related human activities on catchment streamflow time series can facilitate understanding of streamflow response to external factors, including climatic inputs. This study selects the Goulburn River catchment that is located in southeastern Australia having more than 100 years of streamflow observations and more than 90 years of mining history, and divides the streamflow period from 1913 to 2015 into four sub-periods: 1913–1920 (no mining), 1921–1950 (small-scale underground mining), 1951–1980 (commence of new underground mining) and 1981–2015 (large-scale mining of open cut and underground mining). Process-based hydrological modelling (SIMHYD), simple one-parameter hydrological model (Budyko-based method) and a data-driven approach (the double mass curve, DMC), are used to assess mining-related centennial streamflow changes and to quantify relative contributions of climate variability and mining activities on streamflow. These results show that streamflow increased during periods of underground mining, which is likely due to over-pumping to sustain the underground mining. The difference between the observed streamflow and the SIMHYD simulated was very marginal in the reference period of 1913–1920; while it increased by 3.39 mm yr−1 in 1921–1950 and by 10.51 mm yr−1 in 1951–1980. The DMC slope increased from 0.021 in 1913–1920 to 0.025 in 1921–1950, then 0.033 in 1951–1980. These impacts of underground mining on increased streamflow have been greatly reduced and even become negative when open cut mining was largely expanded. The average difference of streamflow during the period of 1981–2015 was reduced from 10.51 mm yr−1 to 2.84 mm yr−1. The DMC slope decreased from 0.033 in 1951–1980 to 0.027 in 1981–2015. The contributions between climate changes and mining activities to streamflow changes estimated using these methods are consistent in trends in different mining periods, but noticeably different in magnitudes. [ABSTRACT FROM AUTHOR]

Vegetation greenness is crucial for assessing vegetation dynamics and evaluating the effectiveness of ecological governance on the Loess Plateau. In this study, we utilized Google Earth Engine (GEE) platform and Landsat image to investigate the spatiotemporal evolution of vegetation greenness and the shift of vegetation greenness lines (VGLs) during the growing season on the Loess Plateau from 1987 to 2020. The driving factors were analyzed using a geographic detector. The results show that the average annual growth rates of NDVI and EVI in the Loess Plateau growing season from 1987 to 2020 were 0.0042/year (P < 0.01) and 0.0023/year (P < 0.01), respectively, with the growth rate after 2000 being three to four times higher. Spatially, significant increases of 78.8% in NDVI and 69.2% in EVI were observed across the entire area of the Loess Plateau. Furthermore, the average VGL based on NDVI and EVI on the Loess Plateau from 1987 to 2020 exhibited a northwestward shift at a rate of 9.79 km/year. This shift resulted in an average movement of 271.83 km over the period. The most significant shifts occurred between 2005 and 2010. Land use and precipitation emerged as the predominant driving factors influencing both the change in vegetation greenness and the shift of the VGLs. Land use and precipitation are the primary factors influencing changes in vegetation greenness and the shift of the VGLs. Land use explains 49.7% of the variation in vegetation greenness, while precipitation accounts for 43%. The combined influence of land use and precipitation explains 68% of the variation in vegetation greenness on the Loess Plateau. Prolonged growing seasons due to climate changes and the "Grain for Green" Project significantly contributed to increased vegetation greenness and northward VGL shifts. Our study offers valuable insights into the spatiotemporal dynamics of vegetation greenness and the shift of VGLs, enhancing our understanding and providing guidance for effective vegetation restoration efforts on the Loess Plateau. • The greening of vegetation causes a northwestward shift in vegetation greenness line. • The vegetation greenness line is shifting northwest at a rate exceeding 9 km/year. • Combined land use and precipitation explain 68% of vegetation greenness variation. [ABSTRACT FROM AUTHOR]

Global climate change has contributed to frequent occurrence of extreme precipitation events, resulting in more severe natural disasters and restricting regional development. The Qinling-Daba mountains region (Qinba) is a transitional zone in central China with high ecological vulnerability and sensitivity. It is therefore essential to investigate the dynamics of precipitation extremes in the region. In this study, spatiotemporal variations of extreme precipitation events were analyzed at the monthly, seasonal and annual timescales based on long-term daily precipitation dataset at 30 meteorological stations over the Qinba during 1961–2017. The results indicated all of the selected ten extreme precipitation indices exhibited non-significant trends at the annual scales. Seasonally, most of extreme precipitation indices decreased in spring, autumn and winter, and increased in summer, whereas consecutive dry days (CDD) increased in all seasons. At the monthly scales, wet precipitation extremes mostly occurred in July, and upward trends of extreme precipitation events dominated in February, June, July and August except for CDD. Spatially, regionwide increases in extreme precipitation events mainly distributed in the eastern and southern Qinba, whereas the north and west were dominated by decreasing trends. Most of atmospheric circulation indices, especially Arctic Oscillation (AO), Southern Oscillation Index (SOI) and Western Pacific Index (WP) were associated with extreme precipitation events at monthly and annual scales. East Asian Summer Monsoon Index (EASMI) and South China Sea Summer Monsoon Index (SCSSMI) strongly influenced extreme precipitation events in summer over the Qinba. Our results are conducive to understanding the variations of extreme precipitation events at the monthly, seasonal and annual scales, and these will be valuable for formulating the corresponding countermeasures at different timescales over the Qinba. [ABSTRACT FROM AUTHOR]

Understanding the relative contributions of climate change and human activities to variations in sediment load is of great importance for regional soil, and river basin management. Considerable studies have investigated spatial-temporal variation of sediment load within the Loess Plateau; however, contradictory findings exist among methods used. This study systematically reviewed six quantitative methods: simple linear regression, double mass curve, sediment identity factor analysis, dam-sedimentation based method, the Sediment Delivery Distributed (SEDD) model, and the Soil Water Assessment Tool (SWAT) model. The calculation procedures and merits for each method were systematically explained. A case study in the Huangfuchuan watershed on the northern Loess Plateau has been undertaken. The results showed that sediment load had been reduced by 70.5% during the changing period from 1990 to 2012 compared to that of the baseline period from 1955 to 1989. Human activities accounted for an average of 93.6 ± 4.1% of the total decline in sediment load, whereas climate change contributed 6.4 ± 4.1%. Five methods produced similar estimates, but the linear regression yielded relatively different results. The results of this study provide a good reference for assessing the effects of climate change and human activities on sediment load variation by using different methods. [ABSTRACT FROM AUTHOR]

The middle reaches of the Yellow River Basin transport the vast majority of sediment (> 85% of the basin's total available sediment load), which has had profound effects on the characteristics of the middle and lower reaches of the Yellow River. Since the late 1950s, soil and water conservation measures have been extensively implemented in the Loess Plateau, China, especially since the 1970s. This has resulted in sediment discharge changing significantly. In this study, data from 22 catchments in the region of the Loess Plateau from Hekou to Longmen in the middle reaches of the Yellow River were analyzed to investigate the responses of the sediment regime to climate change and human activities. The non-parametric Mann–Kendall test and the Pettitt test were used to identify trends and shifts in sediment discharge. All 22 catchments had a significantly decreasing trend ( P < 0.01) in annual sediment discharge. Change point years were detected between 1971 and 1994, and were concentrated between 1978 and 1984 in 17 catchments. Moreover, erosive rainfall exhibited a tendency to decrease, but this was not a significant trend. Compared to rainfall, human activities, primarily soil and water conservation and environmental rehabilitation campaigns, have played a more prominent role in the changes in sediment regimes. In order to reduce soil erosion and sediment yield, more attention should be paid to proper and rational soil and water conservation and eco-restoration in this region. [ABSTRACT FROM AUTHOR]