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An accurate and complete rainfall record is prerequisite for climate studies. The purpose of this research study was to evaluate the homogeneity of the rainfall series for the Mae Klong River Basin in Thailand. Monthly rainfall data of eight stations in the Mae Klong River Basin for the period 1971–2015 were used. The double mass curve analysis was used to check the consistency of rainfall data, whereas the absolute homogeneity was assessed using the Pettitt test, standard normal homogeneity test, Buishand test, and von Neumann test at a 5% significance level. The results of these tests were qualitatively classified as ‘useful’, ‘doubtful’, and ‘suspect’ according to the null hypothesis. Results of the monthly time series indicated the rainfall data as ‘useful’ for 75% of the stations, while two stations’ data were classified as ‘doubtful’ (Stn130221) and ‘suspect’ (Stn376401). On an annual scale, seven out of eight stations data were classified as ‘useful,’ while one station (Stn376401) data were classified as ‘suspect’. Double mass curve analysis technique was used for the adjustment of inhomogeneous data. The results of this study can help provide reliable rainfall data for climate studies in the basin.

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

Quantifying the relative contributions of climate change and human activities to water and sediment variations is of great importance for regional resources and river basin management, which has become a hot topic in hydrology research. In this study, water discharge and sediment load in Xiangxi River basin of Three Gorges Reservoir area were investigated based on hydrometeorological time series since 1960s. The non-parametric Mann-Kendall (M-K) test was used to detect both the trends and abrupt changes in the time series. Double mass curve and sediment rating curve method were used to quantify and evaluate the climatic and anthropogenic effects on water discharge and sediment load. Results indicated that both water discharge and sediment load showed significant decreasing trends with annual decrement rate of –0.08 × 108 and ‒1.011 × 104 t/yr, respectively. The abrupt change points were observed in 1991 for water discharge and 1999 for sediment load by sequential M-K test and cumulative anomaly curve analysis. This study demonstrated that water discharge was mainly influenced by precipitation in 1990s while by human activities ever since 2000, and sediment load was predominantly influenced by human activities (relative contribution 86–98%, regardless of whether the effect is negative or positive). In this study, soil and water conservation as well as land use change were primarily responsible for water and sediment variations in Xiangxi river basin especially since 2000. Further studies need to be done to quantify the importance of a specific driving factor at multi-timescales.

Soil and water conservation are important measures in regulating runoff and sediment load on the Loess Plateau. Information on how land use and land cover changes, especially the implementation of the soil and water loss control project, can affect the sediment load dynamics and hydrological variables is important since large-scale eco-environmental governance programs are being implemented. In this study, an improved double mass curve and the decomposition method were used to assess the effects of different soil and water control measures on runoff and sediment load in the Lvergou, which is a small basin on the Loess Plateau in China, based on 60 years of data. We conclude that the total precipitation (P) was not statistically significantly different (p > 0.05), whereas heavy rain increased significantly (p

The Yom River is one of the four major sediment sources to the Chao Phraya River in Thailand. Human activities and changes in climate over the past six decades may have affected the discharge and sediment load to some extent. In the current study, the river discharge and sediment characteristics in the mainstream of the Yom River were investigated using the field observation data from 2011 to 2013 and the historical river flow and sediment data from 1954 to 2014 at six hydrological stations operated by the Royal Irrigation Department of Thailand (RID). The non-parametric Mann-Kendall test and double mass curve were used to analyze the sediment dynamics and temporal changes in the discharge of the Yom River. The results revealed that the sediment was mainly transported in suspension, and the bed-to-suspended sediment loads ratio varied between 0 and 0.05. The daily suspended sediment load (SSL) in the upper and middle basins had a strong correlation with the daily discharge and could be represented by power equations with coefficients of determination higher than 0.8. The daily suspended sediment load in the lower basin did not directly depend on the corresponding discharge because of the reduction in river slope and water diversion by irrigation projects. It also appeared that the river discharges and sediment loads were mainly influenced by climate variation (floods and droughts). Moreover, the average sediment transport of the upper, middle, and lower reaches were 0.57, 0.71, and 0.35 million t/y, respectively. The sediment load in the lower basin decreased more than 50% as a result of changes in the river gradient (from mountainous to floodplain areas). The results from sediment analysis also indicated that the construction of the Mae Yom Barrage, the longest diversion dam in Thailand, and land-use changes did not significantly affect the sediment load along the Yom River.

Coal mining and soil-water conservation are the two major human interventions on the Loess Plateau in China. Analyzing their impacts on hydrological processes is of great significance for sustainable water resource management. Using hydrological simulation (Soil and Water Assessment Tool, SWAT) and a data-driven method (double mass curve, DMC), the contributions of these two human activities and climate change to the runoff decrease were analyzed in the upper Fenhe River. The runoff in the three affected periods (1967–1987, 1988–1994, and 1995–2017) decreased by 7.5%, 28.2%, and 24.1%, respectively, compared with the base period (1957–1966). In the first affected period (1967–1987), the amount of coal mining activities was small, human activities had little impact on runoff. In the second (1988–1994) and third (1995–2017) periods, as the coal mining and soil-water conservation intensified, their contributions to the runoff decrease rapidly increased. Due to the uncertainties in the model structure and parameters, in addition to the impact of the data accuracy, the results obtained from the two methods were different, but the proportions and the trends of the contribution rates in the different periods were consistent.

Determining the contributions of climate change and human activities to runoff variation is important for water resource management. An improved double mass curve method (IDMC), which can d...

Response of water and sediment generation to climate change and anthropogenic activities is becoming a hot topic in the middle reach of the Jinsha River Basin. In this research, coefficients of variation and concentration degree (i.e., Cᵥ and Cd) and double mass curve (DDC) were adopted to examine the changes in water and sediment discharge and their relationships with precipitation. The contribution rates of climatic and anthropogenic factors to water and sediment discharge were assessed through comparisons between the measured and predicted values in the baseline and postbaseline periods in the basin. The main results were: (a) the water and sediment discharges of the basin showed a decreasing trend from 2006 to 2014, with peak points of Cᵥ and Cd of sediment discharge of the basin in 2009 and 2010, respectively; (b) the precipitation had a major influence on water discharge variations, and the peak point of the DDC of the cumulative precipitation and sediment discharge was consistent with the cumulative water and sediment discharge; and (c) under annual and flooding season scales, the contribution rates of anthropogenic factors to water discharge were 63.060% and 70.457%, respectively. The contribution rates of anthropogenic factors on sediment discharge were 84.790% and 85.541%, respectively. The impacts of anthropogenic factors on water and sediment discharge were more significant than the impacts of precipitation, in which the construction and operation of cascade hydropower stations (CHS) were believed to play a crucial role.

The water resources in arid and semi-arid regions are critical to providing reliable sources of water for food production and ecosystem functioning. In this study, continuous wavelet transform and wavelet coherence were used to analyse the runoff periodicity and relationship with climate indices, respectively. Additionally, the double mass curve (DMCD), the slope changing ratio of cumulative quantity (SCRCQ) and the Choudhury–Yang equation (Budyko-CY) methods for different potential evapotranspiration data (E0(E0-20 cm, E0-PM, E0-H)) were used to separate the impacts of climate changes and anthropogenic activities on runoff variations. The results demonstrated that the flow regimes in high and low flow seasons were not obvious shifts, and that after implementation of the Ecological Water Diversion Project (EWDP), ecosystems were gradually restored in the downstream portion of the Heihe River Basin (DHRB). Periodicities of 1–7 years and 1–5.8 years were detected in Yingluoxia and Zhengyixia, respectively. Additionally, on a 1–148.2 month timescale, the monthly runoff with AO, NAO, PDO, and AMO had significant resonance periodicity and a 1–48 month Spearman's lag correlation. On the annual and high-flow, climate changes dominant determinant to an increase of runoff for the DMCD and Budyko-CY in period 2, SCRCQ and Budyko-CY in period 3 for different E0 in the upstream (UHRB). In the midstream (MHRB) region, anthropogenic activities played a dominant role in deducing the runoff by the SCRCQ and Budyko-CY methods for different E0 values in period 3. During the low-flow season, the impact of human activities in the UHRB and climate changes in the MHRB was significant for period 2 and 3. Therefore, the impacts of climate change and human activities on runoff changes caused by the introduction of different E0 on different timescales should be fully considered in the future.

The present study seeks to estimate the water balance that results as a product of the variation of precipitation and temperature over the Chaquilcay microcatchment, a natural system that intercepts with the surface of the Aguarongo Protected Forest in Gualaceo, Ecuador. Four meteorological stations of the National Institute of Meteorology and Hydrology (INAMHI) were studied, which are divided into climatological and pluviometric, with time series of over 30 years, (1982-2015 period). In order to quantify the contributions and losses of water, statistical analyzes of the time series and surveys of in situ information were carried out. The methods used are linear regression, streak test and double mass curve. To fill and validate the series of precipitation and temperature, reference temperatures of the isothermal raster of Ecuador were included in the pluviometric stations. Additionally, a digital elevation model (MDE) was used to predict the amount of sunshine, and the Thornthwaite evapotranspiration method (1948) was applied from the obtained data. The results show acceptance of the meteorological records, while in the soil analysis we obtained the following data: Humidity, 62.38%; organic matter, 21.29%; field capacity, 18.71 mm and a flow of 1.89 m³ / s during the month of May. Finally, the water balance indicates 843.7 mm of annual precipitation, a storage difference of 18.71 mm representing 2.22% of total precipitation, an surplus of 144.5 mm, and actual evapotranspiration of 680.5 mm, with 17.13% and 80.65%, respectively.

Human activities are increasingly recognized as having a critical influence on hydrological processes under the warming of the climate, particularly for dam-regulated rivers. To ensure the sustainable management of water resources, it is important to evaluate how dam construction may affect surface runoff. In this study, using Mann–Kendall tests, the double mass curve method, and the Budyko-based elasticity method, the effects of climate change and human activities on annual and seasonal runoff were quantified for the Yellow River basin from 1961–2018, additionally, effects on runoff were assessed after the construction of the Xiaolangdi Dam (XLD, started operation in 2001) on the Yellow River. Both annual and seasonal runoff decreased over time (p &lt, 0.01), due to the combined effects of climate change and human activities. Abrupt changes in annual, flood season, and non-flood season runoff occurred in 1986, 1989, and 1986, respectively. However, no abrupt changes were seen after the construction of the XLD. Human activities accounted for much of the reduction in runoff, approximately 75–72% annually, 81–86% for the flood season, and 86–90% for the non-flood season. Climate change approximately accounted for the remainder: 18–25% (annually), 14–19% (flood season), and 10–14% (non-flood season). The XLD construction mitigated runoff increases induced by heightened precipitation and reduced potential evapotranspiration during the post-dam period, the XLD accounted for approximately 52% of the runoff reduction both annually and in the non-flood season, and accounted for approximately −32% of the runoff increase in the flood season. In conclusion, this study provides a basic understanding of how dam construction contributes to runoff changes in the context of climate change, this information will be beneficial for the sustainable management of water resources in regulated rivers.

The damming of rivers has altered their hydrological regimes. The current study evaluated the impacts of major hydrological interventions of the Zhikong and Pangduo hydropower dams on the Lhasa River, which was exposed in the form of break and change points during the double-mass curve analysis. The coefficient of variability (CV) for the hydro-meteorological variables revealed an enhanced climate change phenomena in the Lhasa River Basin (LRB), where the Lhasa River (LR) discharge varied at a stupendous magnitude from 2000 to 2016. The Mann–Kendall trend and Sen’s slope estimator supported aggravated hydro-meteorological changes in LRB, as the rainfall and LR discharge were found to have been significantly decreasing while temperature was increasing from 2000 to 2016. The Sen’s slope had a largest decrease for LR discharge in relation to the rainfall and temperature, revealing that along with climatic phenomena, additional phenomena are controlling the hydrological regime of the LR. Reservoir functioning in the LR is altering the LR discharge. The Soil and Water Assessment Tool (SWAT) modeling of LR discharge under the reservoir’s influence performed well in terms of coefficient of determination (R2), Nash–Sutcliffe coefficient (NSE), and percent bias (PBIAS). Thus, simulation-based LR discharge could substitute observed LR discharge to help with hydrological data scarcity stress in the LRB. The simulated–observed approach was used to predict future LR discharge for the time span of 2017–2025 using a seasonal AutoRegressive Integrated Moving Average (ARIMA) model. The predicted simulation-based and observation-based discharge were closely correlated and found to decrease from 2017 to 2025. This calls for an efficient water resource planning and management policy for the area. The findings of this study can be applied in similar catchments.

Human activities have substantially altered present-day flow regimes. The Headwater Area of the Yellow River (HAYR, above Huanghe’yan Hydrological Station, with a catchment area of 21,000 km2 and an areal extent of alpine permafrost at ~86%) on the northeastern Qinghai-Tibet Plateau, Southwest China has been undergoing extensive changes in streamflow regimes and groundwater dynamics, permafrost degradation, and ecological deterioration under a warming climate. In general, hydrological gauges provide reliable flow records over many decades and these data are extremely valuable for assessment of changing rates and trends of streamflow. In 1998–2003, the damming of the Yellow River by the First Hydropower Station of the HAYR complicated the examination of the relations between hydroclimatic variables and streamflow dynamics. In this study, the monthly streamflow rate of the Yellow River at Huanghe’yan is reconstructed for the period of 1955–2019 using the double mass curve method, and then the streamflow at Huagnhe’yan is forecasted for the next 20 years (2020–2040) using the Elman neural network time-series method. The dam construction (1998–2000) has caused a reduction of annual streamflow by 53.5–68.4%, and a more substantial reduction of 71.8–94.4% in the drier years (2003–2005), in the HAYR. The recent removal of the First Hydropower Station of the HAYR dam (September 2018) has boosted annual streamflow by 123–210% (2018–2019). Post-correction trends of annual maximum (QMax) and minimum (QMin) streamflow rates and the ratio of the QMax/QMin of the Yellow River in the HAYR (0.18 and 0.03 m3·s−1·yr−1 and −0.04 yr−1, respectively), in comparison with those of precorrection values (−0.11 and −0.004 m3·s−1·yr−1 and 0.001 yr−1, respectively), have more truthfully revealed a relatively large hydrological impact of degrading permafrost. Based on the Elman neural network model predictions, over the next 20 years, the increasing trend of flow in the HAYR would generally accelerate at a rate of 0.42 m3·s−1·yr−1. Rising rates of spring (0.57 m3·s−1·yr−1) and autumn (0.18 m3·s−1·yr−1) discharge would see the benefits from an earlier snow-melt season and delayed arrival of winter conditions. This suggests a longer growing season, which indicates ameliorating phonology, soil nutrient availability, and hydrothermal environments for vegetation in the HAYR. These trends for hydrological and ecological changes in the HAYR may potentially improve ecological safety and water supplies security in the HAYR and downstream Yellow River basins.

Global climate change and human activities have important effects on the water discharge and sediment load of the Pearl River. In this study, the water discharge and sediment load were investigated by using hydro-meteorological data from 1954 to 2018. The linear regression, Mann–Kendall abrupt test and double mass curve were employed to detect trends and abrupt change-points in water discharge and sediment load and to quantify the effects of climate change and human activities on water discharge and sediment load. The results revealed that the annual sediment load exhibited a significant decreasing trend at a rate of − 2.24 × 104 t/year, regardless of water discharge, and an abrupt change occurred in 1998. Human activities, especially dam construction contributed 96% to this change, while 4% was due to climate change. El Niño/Southern Oscillation (ENSO) events are often associated with low precipitation, resulting in low water discharge and sediment load, indicating that changes in ENSO periodicity could affect the inter-annual periodic variations of water discharge and sediment load. As population and economy boom, more dams are being built in the Pearl River basin, and special attention should be paid to the management and mitigation of the effects of dams on sediment load.

The impact of human activities and rainfall variability on river discharge is of main concern for policymakers in the Komadugu-Yobe Basin (KYB), Lake Chad area. The KYB is of strategic importance because its rivers contribute significantly to the recharge of Lake Chad whose shrinkage has been of concern to policymakers and the international society. This study investigates the variations in river discharge of the KYB as a result of the contributory effects of rainfall variability and human influences, using daily rainfall and discharge data between 1971 and 2013. In order to partition the impacts of rainfall variability and human activities on river discharge, breakpoints related to abrupt environmental changes caused by human activities are identified using the generalized variance (GV), double mass curve (DMC) and the wavelet spectral methods. Breakpoints are found in 1974 and 1993, which correspond to times when major dams in the basin became operational. These breakpoints may also be related to LULC changes. The land-use land-cover (LULC) analysis shows an increase in bare surface, plantation, settlements and water bodies from 1975 to 2013, in association with a decrease in the forest and grassland coverage. Overall, the mean discharge between the pre-break and post-break periods increased by 24%. This increment in discharge was caused by approximately 50% rainfall variability and 50% human activities. Hence, the effects of human activities appear to be as important as the effect of natural rainfall variability on the river discharge changes in the KYB.

It is critical to determine soil erosion rates and sediment yields under ecological restoration conditions on the Loess Plateau. Sediments retained in check-dams document the soil erosion history in a small watershed. We selected the check-dam systems to reconstruct the long-term sediment yield in a restored agricultural catchment on the Loess Plateau. The storage capacity curve method was applied to estimate the total sediment deposition of check-dam systems, and 725.82 thousand tons of sediment was trapped in the check-dams systems from 1975 to 2013. Two abrupt change points were detected in 1987 and 2003 using the double mass curve method; the average catchment sediment yields were 5,273.63 t/(km2·a) in Stage-1 (1975–1987), 1,734.09 t/(km2·a) in Stage-2 (1988–2003), and 2,653.10 t/(km2·a) in Stage-3 (2004–2013), represented intense erosion, mild erosion, and moderate erosion, respectively. In Stage-2, the sediment yield variation in the Fangta catchment was mainly affected by human activities, and its contribution reached 97%. According to the hierarchical cluster analysis, the soil erosion intensity changed gradually from mild to moderate and then to intense when the average annual erosive rainfall reached approximately 300, 350, and 400 mm in the Fangta catchment of the loess hilly-gully region. Approximately 6.1–42.6 % of the sediment was deposited along the way since 2003 when the sediments generated by erosion in small watersheds were gradually transported to the downstream river network. Therefore, check-dam systems are important carriers for reconstructing the historical sediment yield in small and ungauged watersheds. The results of this study not only serve as a basis for obtaining reliable information on erosion and sediment yield in small dam-controlled catchments, but also provide a useful reference for implementing sustainable ecological restoration in the future.

Climate change and human activities have substantially changed hydrological and geomorphologic processes, particularly in upper mountainous catchments. The Jinsha River Basin (JRB), the uppermost region of the Yangtze River and the largest hydropower production region in China, was chosen to investigate the sediment load responses to climate variations and human activities. The non-parametric Mann-Kendall test and double mass curve were used to explore the spatial-temporal variations of hydro-meteorological variables and quantify the contributions of climate variation and human activities to changes in discharge and sediment load in the JRB from the 1950s to 2015. The results indicate that human activities, in particular cascade damming, were the governing factor for sediment load changes, while climate variations (increasing precipitation and snow and glacier melt) dominated the discharge changes in the JRB. The average annual sediment load at the Panzhihua (PZH) station increased by 42.4% from 1966–1984 to 1985–2010, mainly due to mineral extraction and deforestation, followed by a decrease of 75.9% in 2011–2015 because of the operation of the cascade reservoirs in the middle JRB since 2010. The construction of new dams like the Xiangjiaba Reservoir (2012) and the Xiluodu Reservoir (2013) in the lower JRB and many other cascade reservoirs since 2010 in the middle JRB further decreased the sediment load by 58.5% (BHT) and 83.8% (XJB) in the recent five years from 2011 to 2015. Although channel erosion downstream of the XJB Dam can provide new sediment to the Three Gorges Reservoir (TGR), the sedimentation rate of the TGR has decreased rapidly and will continue to be reduced due to the construction of more dams in the future.

Water resources and engineering projects are of major importance due to great demand of water and power supplies, irrigation needs, drought mitigation and flood control. In order to plan and design these projects, complete and reliable hydrological datasets are required. Missing data can severely compromise data quality and utility. The Rufiji Water Basin Office has developed and kept a database of daily streamflow records from 1950s to-date for at least 87 gauging stations. While the majority of the records are complete, data checks revealed significant gaps. Some stations are experiencing large gaps of up to 19 consecutive years. There is no dedicated study that looked at assessment of suitable methods for infilling such gaps. This study therefore made a contribution by appraising empirical and regression rainfall runoff based methods in the Little Ruaha River catchment, a sub-catchment of the Great Ruaha River sub-basin both within the Rufiji River Basin. The methods employed included simple linear regression (with untransformed and log-transformed data), multiple linear regression (with untransformed and log-transformed data), rainfall-runoff relationship using double mass curve technique, flow duration matching and drainage-area ratio. In addition, rainfall runoff modeling using HBV-Light was done for further comparison. With exception to the rainfall-runoff relationship and HBV-Light model, all other methods relied upon data transfer from donor stations (upstream & downstream station(s)) for infilling a downstream/upstream station. Data quality and consistency checks were performed, and performances of infilling methods were evaluated based on three performance criteria namely Nash-Sutcliffe efficiency coefficient (NSE), Coefficient of determination (R2) and standard error of estimate (SE) during calibration and validation periods. Four gauging stations (2 each upstream and downstream) were separately used to infill artificially created gaps to the target station. Overall, the calibration and validation daily results at 1KA21A indicated that the flow duration matching technique and multiple linear regression methods performed better than other methods with NSE (71%; 93%) and NSE (55%; 75%) respectively. These results have a potential for wide application in other basins of Tanzania for hydrological analysis and water resource management, where missing data is very common.

Analyzing intra-annual stream flow can reveal the main causes for runoff changes and the contributions of climate variability and human activities. For this purpose, the Mann–Kendall and cumulative rank difference (CRD) tests, and the double mass curve method, were applied to a time series of hydro-meteorological variables from 1971 to 2010 in the Tajan River basin in Iran. Results indicated that runoff changes in the wet and dry seasons after 1999 had significant respective decreasing and increasing trends, at the 0.01 confidence level, due to dam construction. In the pre-dam period (1991–1998), the results of the double mass curve method showed that climate variability and human activities contributed 57.76% and 42.24%, respectively, to the runoff decrease during the wet season. For the post-dam period (1999–2010), climate variability and anthropogenic activities contributed 24.68% and 75.32%, respectively, to the wet season runoff decrease of 116.55 mm. On the other hand, in the same period during the dry season, climate variability contributed −30.68% and human activities contributed 130.68% to the runoff increase of 41.45 mm. It is evident that runoff changes in both wet and dry seasons were mainly due to human activities associated with dam construction to meet water supply demands for agriculture.

Accelerated soil erosion exerts adverse effects on water and soil resources. Rainfall erosivity reflects soil erosion potential driven by rainfall, which is essential for soil erosive risk assessment. This study investigated the spatiotemporal variation of rainfall erosivity and its impacts on sediment load over the largest freshwater lake basin of China (the Poyang Lake Basin, abbreviate to PYLB). The spatiotemporal variations of rainfall erosivity from 1961 to 2014 based on 57 meteorological stations were detected using the Mann–Kendall test, linear regression, and kriging interpolation method. The sequential t test analysis of regime shift (STARS) was employed to identify the abrupt changes of sediment load, and the modified double mass curve was used to assess the impacts of rainfall erosivity variability on sediment load. It was found that there was significant increase (P

Mo, S.; Li, Z.; Gou, K.; Qin, L., and Shen, B., 2018. Quantifying the effects of climate variability and direct human activities on the change in mean annual runoff for the Bahe River (Northwest China). Evaluating the impacts of climate change and human interference on runoff is critically important for regional water security. This study investigated the effects of climate variability and direct human activities on the change in mean annual runoff for the Bahe River in Northwest China. Precipitation, evaporation, and runoff data from 1959 to 2010 were analyzed at the Luolicun and Maduwang hydrologic gauge stations, and their temporal trends were explored using the Mann-Kendall test. A Mann-Kendall-Sneyers test and the double mass curve were applied to detect the statistically significant transition points in the hydrometeorological records. Results indicated no change point in upstream runoff in the Bahe River from 1959 to 2010; however, a clear transition point existed in midstream runoff in 19...

The water discharge and sediment load of rivers are changing substantially under the impacts of climate change and human activities, becoming a hot issue in hydro-environmental research. In this study, the water discharge and sediment load in the mainstream and seven tributaries of the Yangtze River were investigated by using long-term hydro-meteorological data from 1953 to 2013. The non-parametric Mann-Kendall test and double mass curve (DMC) were used to detect trends and abrupt change-points in water discharge and sediment load and to quantify the effects of climate change and human activities on water discharge and sediment load. The results are as follows: (1) the water discharge showed a non-significant decreasing trend at most stations except Hukou station. Among these, water discharge at Dongting Lake and the Min River basin shows a significant decreasing trend with average rates of -13.93×108m3/year and -1.8×108m3/year (P

Design of urban drainage infrastructure depends on the rainfall pattern and runoff volumes. Under the current impacts of urbanization and industrialization in the Kingdome of Saudi Arabia (KSA), there is a need to review the guidelines for design of drainage infrastructure. In this study, a methodology is developed to investigate the impact of variations in rainfall on the capacity of drainage infrastructure for the city of Madinah (Taibah), KSA. Rainfall data collected from Madinah Municipality was analyzed to determine the normal annual rainfall (average of the annual rainfall for 30 years). Data consistency was checked using double mass curve technique, and the design rainfall (DR) was estimated by Gumbel Extreme Value Distribution. The Mann-Kendall test was run at 5% significance level on rainfall time series over the period 1985–2015; however, no significant trend was observed. Urban drainage schemes are designed for peak flows based on DR. The true values of DR are difficult to estimate due to uncertainties associated with variations in estimation procedures and data limitations. An attempt is made to elaborate the impact of data errors (both systematic and random) on DR to facilitate engineers in selecting safety factor for design of urban drainage infrastructure. The stormwater trunk-sewer was designed to safely convey the runoff for an area around the Masjid-e-Al-Nabawi. Rainfall–runoff modeling was performed by Rational Method to find the peak flow and Nash GIUH. It was found that there is about 20% change in diameter of trunk sewer for change in return period from 2 to 10 years.

Quantitative assessment of the hydrological response to urbanization has been a major concern in hydrology and water resources management. In this study, a procedure combining different statistical methods and a hydrological model to quantify annual runoff response to spatial and temporal variations of impervious surface areas was proposed and applied to the Qinhuai River basin, an urbanized basin located in southeastern China, over the period from 1986 to 2013. The landscape indicators, such as impervious area and number of impervious patches were used to measure the spatial configuration of urbanization and quantify the runoff response to urbanization. Impervious area data were derived from the Landsat images using superior ensemble learning method of rotation forest. The Mann–Kendall test, Sen's estimator, Pettitt test and double mass curve method were applied to examine gradual trend and abrupt changes for hydro-meteorological data series. A hydrological model based on stepwise regression analysis was built and used to explore the relation among annual runoff and precipitation, potential evapotranspiration and landscape indicators. The results showed that annual runoff and runoff coefficient had significant increasing trends and an abrupt change after year 2001 when the watershed impervious area reached 8.6%. The average annual runoff increased by 60%, of which, urbanization was responsible for 59% of the increase, while precipitation changes were responsible for the remaining 1% in the study region. The annual runoff response to impervious area showed a nonlinear relationship, and was more sensitive in dry years than wet years. The changes of impervious area were more remarkable in connecting the existed impervious patches than in developing the new ones beginning in the early 2000s, which increased the watershed's drainage capacity and resulted in the abrupt change of runoff response. The study demonstrated that the proposed procedure was efficient to quantify the runoff responses to urbanization using landscape metrics of impervious surface.

Quantification of runoff is critical to estimate and control water pollution in urban regions, but variation in impervious area and land-use type can complicate the quantification of runoff. We quantified the streamflow contributions of subwatersheds and the historical changes in streamflow in a flood prone urbanizing watershed in US Midwest to guide the establishment of a future pollution-control plan. Streamflow data from five nested hydrological stations enabled accurate estimations of streamflow contribution from five subwatersheds with variable impervious areas (from 0.5% to 26.6%). We corrected the impact of Missouri river backwatering at the most downstream station by comparing its streamflow with an upstream station using double-mass analysis combined with Bernaola-Galvan Heuristic Segmentation approach. We also compared the streamflow of the urbanizing watershed with seven surrounding rural watersheds to estimate the cumulative impact of urbanization on the streamflow regime. The two most urbanized subwatersheds contributed >365 mm streamflow in 2012 with 657 mm precipitation, which was more than fourfold greater than the two least urbanized subwatersheds. Runoff occurred almost exclusively over the most urbanized subwatersheds during the dry period. The frequent floods occurred and the same amount of precipitation produced ~100 mm more streamflow in 2008–2014 than 1967–1980 in the urbanizing watershed; such phenomena did not occur in surrounding rural watersheds. Our approaches provide comprehensive information for planning on runoff control and pollutant reduction in urban watersheds.

In this study, we updated the hydrological data from the 1950s to 2012 and analysed the temporal variations in the hydrological series of the Pearl River using the wavelet transform method. Furthermore, we quantified the climatic and anthropogenic effects on the changes in the hydrological processes in the Pearl River. The results of the combined methods of the wavelet transform method and the Mann-Kendall (MK) trend test (i.e., wavelet trend test) reveal that the water discharge series exhibited a statistically insignificant changing trend since the 1950s; however, the sediment load series displayed a statistically significant decreasing trend. Comparisons of the results of the MK trend test and the wavelet trend test indicate that annual and inter-annual periodic oscillations affect the trend changes in the hydrological series. Statistical analysis and the double mass curve indicate that climatic change dominates changes in water discharge, such as the El Nino Southern Oscillation (ENSO), and human activities were mainly responsible for the phase changes in the sediment load. From 1973 to 1986, deforestation in the basin dominated the sediment variability and caused 83.2% of the increase in the sediment load compared to the reference period of 1957–1972. Even though water and soil conservation projects have been carried out since the early 1990s, the vegetation cover in the catchment area decreased by 6.5 × 10 4 km 2 from the late 1980s to the late 2000s, as detected by Landsat TM images, and water and soil conservation projects had little effect on the sediment reduction. Since the 1990s, dam construction has dominated sediment variability. Compared to the reference period, the sediment load due to dam construction decreased by 83.4 kg/s and 993.3 kg/s in the periods of 1987–1998 and 1998–2006, respectively, and the reduction in the sediment load increased to 1329.5 kg/s in the period of 2007–2012, indicating the intensifying impact of dam construction on the sediment reduction. The sediment sources in the Pearl River basin have changed, and scouring of the river channel has become a new sediment source in response to dam construction. The alteration of hydrological processes in the Pearl River will continue to occur in the future in the context of global climatic change, which is becoming increasingly important for river management in the Pearl River basin.

As one of the fastest developing regions in China, the middle-lower Yangtze River (MLYR) is vulnerable to floods and droughts. With obtained time series of annual highest water level (HWL), annual lowest water level (LWL) and the corresponding river discharges from three gauging stations in MLYR that covering the period 1987–2011, the current study evaluated the change characteristics of annual extreme water levels and the correlation with river discharges by using the methods of trend test, Mann-Whitney-Pettitt (MWP) test and double mass analysis. Major result indicated a decreasing/increasing trend for annual HWL/LWL of all stations in MLYR during the study period. A change point in 1999 was identified for annual HWL at the Hankou and Datong stations. The year 2006 was found to be the critical year that the relationship between annual extreme water levels and river discharges changed in the MLYR. With contrast to annual LWL in MLYR, further investigation revealed that the change characteristics of annual HWL were highly consistent with regional precipitation in the Yangtze River Basin, while the linkage with Three Gorges Dam (TGD) operation is not strong. Our observation also pointed out that the effect of serious down cutting of the riverbed and the enlargement of the cross-section area during the initial period of TGD operation caused the downward trend of the relationship between annual LWL and river discharge. Whereas, the relatively raised river water level before the flood season due to TGD regulation since 2006 explained for the changing upward trend of the relationship between annual HWL and river discharge.

Alpine glaciers and perennial snow fields are important hydrologic elements in many mountain environments providing runoff during the late summer and during periods of drought. Because relatively long records of glacier mass-balance data are absent from many glacierized catchments, it remains unclear to what extent shrinking perennial snow and glaciers have affected runoff trends from these watersheds. Here we employ a hydrograph separation technique that uses a double mass curve in an attempt to isolate changes in runoff due to glacier retreat and disappearance of perennial snow. The method is tested using hydrometric data from 20 glacierized and 16 non-glacierized catchments in the Columbia Basin of Canada. The resulting estimates on cryosphere storage contribution to streamflow were well correlated to other regional estimates based on measurements as well as empirical and mechanistic models. Annual cryosphere runoff changed from +19 to -55% during the period 1975-2012, with an average decline of 26%. For August runoff, these changes ranged from +17 to -66%, with an average decrease of 24%. Reduction of cryosphere contributions to annual and late summer flows are expected to continue in coming decades as glaciers and the perennial snow patches shrink. Our method to isolate changes in late summer cryospheric storage contributions can be used as a first order estimate on changes in glacier contributions to flow and may help researchers and water managers target watersheds for further analysis.

National large-scale soil and water conservation controls on the Gangjiang River basin have been documented, but the effect of governance on regional watershed hydrology and how the main driving factors act have not been systematically studied yet. To do this, this study evaluated changing trends and detected transition years for both streamflow and sediment discharge using long-term historical records at seven hydrological stations in the Ganjiang River basin over the past 50 years. The double mass curve (DMC) method was used to quantify the effects of both climate change and human activities on hydrological regime shifts. The results showed that the distributions of precipitation, streamflow, and sediment discharge within a year are extremely uneven and mainly concentrated in the flood season of Jiangxi Province. None of the stations showed significant trends over time for either annual precipitation or streamflow, while the annual sediment discharge at most stations decreased significantly over time. The estimation of sediment discharge via DMC indicated that after the transition years, there were rapid reductions in sediment discharge at all hydrological stations, and the average decline degree of midstream and downstream were much larger than that of upstream. Human activities, especially the increase of vegetation cover and construction of large and medium-sized reservoirs, provided a significantly greater contribution to the reduction of sediment discharge than did precipitation changes. As a case study of river evolution under global change environment, this study could provide scientific basis for the control of soil erosion and the management of water resources in Ganjiang River, as well as for the related research of Poyang Lake and the Yangtze River basin of China.

Yongding River is the largest river flowing through Beijing, the capital city of China. In recent years, Yongding River Basin (YDRB) has witnessed increasing human impacts on water resources, posing serious challenges in hydrological and ecological health. In this study, remote sensing techniques and statistical time series approaches for hydrological studies were combined to characterize the dynamics and driving factors of reservoir water extents in YDRB during 1985–2016. First, 107 Landsat 4, 5, 7 and 8 images were used to extract surface water extents in YDRB during 1985–2016 using a combination of water indices and Otsu threshold algorithm. Significant positive correlation was found between water extents and the annual inflow for the two biggest reservoirs, the downstream Guanting and upstream Cetian reservoirs, proving their representativeness of surface water availability in this basin. Then, statistical time series approaches including trend-free pre-whitening Mann-Kendall trend test, Pettit change-point test and double mass curve method, which are frequently used in hydrological studies, were adopted to quantify the trend of reservoir water extents dynamics and the relative contributions of climate variability and human activities. Results showed that the water extents in both reservoirs exhibited significant downward trend with change point occurring in 2001 and 2005 for Guanting and Cetian, respectively. About 74%~75% of the shrinkage during the post-change period can be attributed to human activities, among which GDP, population, electricity power production, raw coal production, steel and crude iron production, value of agriculture output, and urban area were the major human drivers. Hydrological connectivity between the upstream Cetian and downstream Guanting reservoirs declined during the post-change period. Since 2012, water extents in both reservoirs recovered as a result of various governmental water management policies including the South-to-North Water Diversion Project. The methodology presented in this study can be used for analyzing the dynamics and driving mechanism of surface water resources, especially for un-gauged or poorly-gauged watersheds.

The Shiyang River Basin is a typical arid watershed in Northwest China. Scientific understanding of the driving mechanism of runoff change is the basis of scientific utilization of water resources and regional sustainable development. In this study, runoff changes at different time scales were analyzed for the period 1960–2018, and the impacts of climate variability and human activities on runoff were investigated in the middle and lower reaches of the Shiyang River Basin (SRB). A combination of mutation analysis and human-designed analysis was adopted to divide the study period into the baseline period and the variation period. The Mann–Kendall test (M−K) and Double Mass Curve method (DMC) were used to detect abrupt changes and quantify the relative effects of climate change and human activities on runoff. The results reveal a significant declining trend in annual runoff on the whole in the middle and lower reaches of the SRB, and there was an obvious recovery trend after the implementation of the Comprehensive Treatment Program of the SRB (CTSRB) in 2007. Abrupt changes occurred in 1976, 1991 and 2007, which divided the study period into the baseline period (1960–1975), the Variation Ⅰ period (1976–1990), the Variation Ⅱ period (1991–2006) and the Variation III period (2007–2018). The contribution of human activities to runoff reduction was 88.72%, whereas the contribution of climate change to runoff reduction was only 11.28%. Furthermore, the contribution of human activities to runoff reduction in the Variation Ⅰ period, Variation Ⅱ period and Variation III period was 89.44%, 93.02% and 83.69%, respectively. Therefore, human activities played the most dominant role in the variation of runoff, followed by climate change and upstream runoff. Further analysis of the impact of human activities on runoff indicated that agricultural irrigation was the dominant factor of runoff reduction. This study can provide detailed information on water resources and a scientific basis for the development and utilization of water resources in the future.

Quantifying the impacts of climate and human activities on water and sediment discharge has become a central topic in climate and hydrologic research. This issue, however, has so far received little attention in karst regions around the world. Seven karst catchments located in southwest China were chosen to explore water and sediment discharge responses to different driving factors during the period from the 1950s to 2011. The non-parametric Mann-Kendall test was used to detect both the trends and abrupt changes in water and sediment discharge. The double mass curve method was used to quantify the effects of climate and human activities on water and sediment discharge. Results indicated that the annual water discharge showed a decreasing trend in all catchments (−0.21 to −3.68 × 108 m3 yr−1), and the sediment discharge exhibited a significant decreasing trend (−7 to −101 × 104 t yr−1) for six out of the seven catchments. A rapid decline (abrupt change) in sediment discharge occurred since 2000 for all except Liujiang catchment where the sediment discharge has a slight increase since 1983 as no large dams were constructed in this catchment. Specifically, the magnitude of reduction in sediment discharge (%) significantly increases with the extent of flow regulation as measured by the ratio of the area upstream the dam to the total catchment area for the seven catchments (R2 = 0.98, P < 0.01). This study demonstrated that water discharge was mainly influenced by precipitation, while sediment discharge was mainly influenced by human activities (relative contribution 70–111%, regardless of whether the effect is negative or positive). Ecological restoration played somehow important roles in the decrease in sediment discharge (negative relationships of sediment discharge with the Normalized Differential Vegetation Index (NDVI)), but dam construction was likely to be the principal cause of the significant decrease in sediment discharge. This study is of use for better catchment management in karst regions in southwest of China.

This study analysed the land-use dynamics and its effects on rainfall–runoff and runoff–sediment relationships at Maybar sub-watershed, Ethiopia. The study compared land use land cover change (LULCC), runoff and sediment load for 1980s, 1990s and 2000 years. A base map produced from ground base survey, aerial photograph, spot images and field visit/interview had been carried out for land cover analysis. Double mass curve with trend curve was used to evaluate the effect of LULCC on rainfall–runoff and runoff–sediment yield relationships. The results showed that during 1990s forest land increased while agricultural and grassland decreased, whereas during 2000s agricultural land increased and forest land decreased. Consequently, the annual slope of trend curve (STC) of rainfall–runoff and runoff– sediment load during 1980s was more pronounced compared with 1990s. Similarly, the annual STCs of 2000s were higher than 1990s despite it is not statistically significant. This implies that, the accumulative...

Non-parametric Mann-Kendall, double mass curve analysis and annual variation analysis were used to analyze the spatial and temporal changes in runoff and sediment loads at the Jiuzhou, Jiajiu and Yunjinghong hydropower stations in the Lancang River from 1964 to 2010. The results indicate that the inter-annual and annual distributions of sediment have significantly changed since the 1990s, and that sediment discharge has increased at the Jiuzhou station, while sediment discharge has declined at the Jiajiu and Yunjinghong stations. Overall, annual runoff distribution patterns have been consistent since the 1990s. Spatial and temporal changes in runoff and sediment loads in the Lancang River have been attributed to the construction of hydropower stations, changes in land use and precipitation patterns. The results can provide guidance for the environmental protection and ecological restoration of rivers in the Southwest of China.

Based on the observed data of monthly precipitation and runoff from 1960 to 2011 in the catchment controlled by the Sandaohezi hydrological station, the double mass curve of precipitation-runoff and Kolmogorov–Smirnov dual sample test were applied to divide the years 1960–2011 into four periods: 1960–1979, 1980–1991, 1992–1999 and 2000–2011. And then, through several trial calculations, a water year of the catchment was divided into wet season and dry season, and the precipitation-runoff dynamic multiple regression (DMR) models were constructed for the four periods. The computed annual runoff values of the DMR models all passed the Fisher test. Besides, the four models' average residuals were all less than 14.15%, and the determination coefficients were all greater than 77.96%. Using the established models, we quantified to what extent the runoff was affected by precipitation variations and streamflow yield capability changes. The result showed that compared with the period of 1960–1979, the annual runoff in 1980–2011 decreased by 14.42% due to precipitation variations and by 23.11% due to streamflow generation condition changes. Furthermore, we found that the runoff of the dry season was dominantly related to the precipitation during the flood season in the previous year.

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

The variation of river runoff (Q) and suspended sediment load (S), in addition to their influential factors, is an important area of focus in hydrological sciences. Here, Mann&ndash, Kendall tests and double mass curve analyses were used with hydrometric data from four hydrological stations in the upper Fenhe River Basin in China to evaluate temporal trends in annual Q (Qa) and S (Sa) values between 1955 and 2015. Based on the observed inflection points, three distinct periods were identified, namely, 1955&ndash, early 1980s (period I), the early 1980s&ndash, 1996 (period II), and 1996&ndash, 2015 (period III). The Qa and Sa values for the four stations, except for Qa values for the Jingle station, significantly decreased over the study period, with average reduction rates of 0.68&ndash, 1.07 mm∙km&minus, 2∙a&minus, 1 and 9.24&ndash, 54.39 t∙km&minus, 1, respectively. Decreased rainfall, implementation of soil and water conservation program, and reservoir construction were primarily responsible for decreased Qa and Sa values for the three stations during period II, while the first two factors led to variation in Qa and Sa for the Jingle station during the same period. During period III, the Qa, Sa, and Qa&ndash, Sa relationships for the four stations were intensively affected by increased anthropogenic activities, including water diversion, cross-basin water transfers, soil and water conservation measures, revegetation efforts, and sand excavation. Further, the Qa, Sa, and Qa&ndash, Sa relationships at the Lancun station were affected by the construction of the No. 2 Fenhe Reservoir. Effective water use and supply strategies should be implemented in the future for the upper Fenhe River Basin.

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.

The goal of the current study is to examine the relative role of watershed disturbance on the seasonal hydrological drought. We propose a new methodology that combines the two-parameter Budyko equation and improved double mass curve (IDMC) technique to remove the effect of climate change from the total change in the seasonal hydrological drought. In particular, we analyze the relative role of watershed disturbance and forest change in the changes of seasonal hydrological drought using Yaak River watershed in Montana, U.S. as an example. The hydrological drought is defined based on the threshold level approach. In addition, the sensitivity of hydrological drought to the changes of forest condition is performed based on the basin average normalized difference vegetation index (NDVI). The proposed method can be applied to quantify the effect of watershed disturbance on the seasonal drought. Seasonal flow shows the different nature of response to the watershed disturbance. Spring flow decrease is primarily due to the watershed disturbance. On the other hand, watershed disturbance offsets climate change effect on summer flows. The changes in hydrological drought due to watershed disturbance decrease (increase) with the threshold during spring (summer). The contribution of forest disturbance to the change in drought due to watershed disturbance during the summer is as large as 75%. The study has a promising potential in hydrological studies because watershed characteristics play a crucial role in terrestrial water storage, evapotranspiration, and discharge.

In northern Iran’s Haraz River basin between 1975 and 2010, hydrological sensitivity, double mass curve, and Soil and Water Assessment Tool (SWAT) methods were applied to monitoring and analysing changes in stream flow brought on by climatic variability and human activities. Applied to analyse trends in annual and seasonal runoff over this period, the sequential MK test showed a sudden change point in stream flow in 1994. The study period was, therefore, divided into two sub-periods: 1975–1994 and 1995–2010. The SWAT model showed obvious changes in water resource components between the two periods: in comparison to the period of 1975–1994, sub-watershed-scale stream flow and soil moisture decreased during 1995–2010. Changes in evapotranspiration were negligible compared to those in stream flow and soil moisture. The hydrological sensitivity method indicated that climatic variability and human activities contributed to 29.86% and 70.14%, respectively, of changes in annual stream flow, while the SWAT model placed these contributions at 34.78% and 65.21%, respectively. The double mass curve method indicated the contribution of climatic variability to stream flow changes to be 57.5% for the wet season and 22.87% for the dry season, while human activities contributed 42.5% and 77.13%, respectively. Accordingly, in the face of climatic variability, measures should be developed and implemented to mitigate its impacts and maintain eco-environmental integrity and water supplies.

Precipitation and human activities are two essential forcing dynamics that influence hydrological processes. Previous research has paid more attention to either climate and streamflow or vegetation cover and streamflow, but rarely do studies focus on the impact of climate and human activities on streamflow and sediment. To investigate those impacts, the Zuli River Basin (ZRB), a typical tributary basin of the Yellow River in China, was chosen to identify the impact of precipitation and human activities on runoff and sediment discharge. A double mass curve (DMC) analysis and test methods, including accumulated variance analysis, sequential cluster, Lee-Heghnian, and moving t-test methods, were utilized to determine the abrupt change points based on data from 1956 to 2015. Correlation formulas and multiple regression methods were used to calculate the runoff and sediment discharge reduction effects of soil conservation measures and to estimate the contribution rate of precipitation and soil conservation measures to runoff and sediment discharge. Our results show that the runoff reduction effect of soil conservation measures (45%) is greater than the sediment discharge reduction effect (32%). Soil conservation measures were the main factor controlling the 74.5% and 75.0% decrease in runoff and sediment discharge, respectively. Additionally, the contribution rate of vegetation measures was higher than that of engineering measures. This study provides scientific strategies for water resource management and soil conservation planning at catchment scale to face future hydrological variability.

The Gongshui River basin exhibits one of the most serious soil erosion areas in southern China, and has always been the key control area of national soil and water conservation programs. This study used daily precipitation, streamflow, and sediment concentration data collected from 1957 to 2015 from the main hydrological stations of the Gongshui River to investigate streamflow and sediment discharge variations and their responses to precipitation and human activities. The Mann-Kendall and Pettitt&rsquo, s test were used for trend and change-point detection. The double mass curve (DMC) method was employed to quantify the effects of precipitation change and human activities on hydrological regime shifts. The results showed insignificant trends of both annual precipitation and streamflow for all stations, while the sediment discharge of most stations exhibited significant decreasing trends. Change-point analyses revealed that all hydrologic stations except Mazhou had transition years. The estimation via DMC indicated that after the change point years, there was a rapid reduction in sediment discharge at Hanlinqiao, Fengkeng, Julongtan, Xiashan, and Chawu stations, but not at Mazhou, Ruijin, and Yangxinjian stations. Human activity provided a significantly greater contribution to sediment discharge than precipitation. The evidence clearly indicates that the degree and extension of conservation or destruction measures and the construction of large- and medium-sized reservoirs were the major factors significantly decreasing or increasing annual sediment discharge of the Gongshui River. This work could serve as the basis for decision making regarding river basin water resources management to estimate the effects of anthropogenic impacts on water and sediment discharge variations during the last few decades, thereby guiding adaptation and protection of the water resources of the Gongshui River flowing into the Poyang Lake.

This study aims to reveal the runoff variation characteristics of long time series in a karst region, analyse comprehensively its different driving factors, and estimate quantitatively the contribution rates of climate change and human activities to net runoff variation. Liudong river basin, a typical karst watershed in southwest China, is the study site. Statistical methods, such as linear fitting, the Morlet wavelet analysis, normalized curve and double mass curve, are applied to analyse the runoff of the watershed. Results show that the runoff in the karst watershed during the research period exhibits a three-stage change and the abrupt change points are the years 1981 and 2007: (1) 1968-1980, the runoff initially exhibited a trend of sustained decreasing and then an abrupt fluctuation. The runoff was obviously destroyed through precipitation-producing processes. Improper land utilisation and serious forest and grass destruction intensified the fluctuation variation amplitude of the runoff. (2) 1981-2006, the changing processes of runoff and precipitation exhibited good synchronism. Precipitation significantly affected runoff variation and human activities had a slight interference degree. (3) 2007-2013, the fluctuation range of runoff was considerably smaller than that of precipitation. The significant growth of forest and grassland areas and the increase in water consumption mitigated runoff fluctuation and greatly diminished runoff variation amplitude. According to calculation, the relative contribution rates of precipitation and human activities to net runoff variation with 1981-2007 as the reference period were -81% and 181% in average, respectively, during 1968-1980, and -117% and 217% in average, respectively, during 2007-2013. In general, the analysis of runoff variation trend and of the contribution rate of its main influencing factors in the typical karst watershed for nearly half a century may be significant to solve the drought problem in the karst region and for the sustainable development of the drainage basin.

This paper aims to analyze the effects of precipitation and anthropogenic activity on hydrologic features in Yanhe River so as to provide support for regional water management and evaluation of water and soil conservation measures. Thiessen Polygon was created to calculate mean values of watershed, and Mann-Kendall statistic test and Sen’s slop estimator test were adapted to analyze variation trend and interaction between precipitation, runoff, and sediment discharge. When 1961~1970 was set as reference period (ignoring human effects), the double mass curve quantified the effects of precipitation and anthropogenic activity on runoff and sediment discharge in Yanhe River during 1961~2008. The result showed that the monthly distribution of precipitation, runoff, and sediment discharge was extremely uneven. 78.1% of precipitation, 64.1% of runoff, and 98.6% of sediment discharge occurred in the flood season. Precipitation, runoff, and sediment discharge performed significant downward trends during 1961–2008. Therein, anthropogenic factors contributed 66.7% and 51.1% to sediment discharge reduction during 1971–1994 and 1995–2008, respectively. They contributed 103.8% and 82.9% to runoff reduction during these two periods, respectively.

In this paper, the Mann-Kendall test and F-test were combined to analyze the annual and seasonal streamflow variations and aberrance points for the twin rivers from 1963 to 2011. The Tennant method was subsequently used to evaluate the ecological flow assurance and deficit. Finally, the Double Mass Curve method was applied to identifying the human activities affecting the streamflow variations. The results were as follows: (1) Three similar stages of the streamflow variations were found for the twin rivers: fluctuations before 1980, the tiny downward trends from the 1980s to the 1990s, and the notably downward trends in the 2000s. (2) The seasonal streamflow also decreased continuously and dramatically, especially in summer, by 80.9% for the Chaohe River and 86.0% for the Baihe River. (3) During the spawning season, 83.3% and 73.1% of streamflow was not at the appropriate level for the Chaohe and Baihe Rivers, respectively, which indicated that the ecological environment was not optimal for the reproduction and breeding of aquatic organisms. While in other periods, the ecological flow assurance was better than that in spawning seasons for the Chaohe and Baihe Rivers, respectively. This indicated that the streamflow regimes of the twin rivers were not always optimal and conducive to the development of the aquatic ecosystem. (4) The streamflow variations of the twin rivers were influenced by increasingly intensive human activities such as changes of land use and land cover, and excessive exploitation and utilization of water resources. These influences were cumulative and showed a gradually increasing tendency. This research is helpful for understanding the streamflow regime and for forecasting of the regional extreme climate, such as drought and floods, and can provide a basis for decision making and formulating adaptive ecological security countermeasures in response to climate changes and human activities.

In this research, monthly hydrological and daily meteorological data were collected across China for the period 1956–2012. Modified Mann–Kendall tests, double mass curve analysis, and correlation statistics were performed to identify the long-term trends and interrelation of the hydrometeorological variables and to examine the influencing factors of streamflow and sediment. The results are as follows: (1) In the last 60 years, the streamflow in northern China has shown different decreasing trends. For the southern rivers, the streamflow presented severe fluctuations, but the declining trend was insignificant. For the streamflow in western China, an increasing trend was shown. (2) In the northern rivers, the streamflow was jointly controlled by the East Asian monsoon and westerlies. In the southern rivers, the runoff was mainly influenced by the Tibet–Qinghai monsoon, the South Asian monsoon, and westerlies. (3) Sediment loads in the LCRB (Lancang River Basin) and YZRB (Yarlung Zangbo River Basin) did not present significant change trends, although other rivers showed different degrees of gradual reduction, particularly in the 2000s. (4) Underlying surface and precipitation changes jointly influenced the streamflow in eastern rivers. The water consumption for industrial and residential purposes, soil and water conservation engineering, hydraulic engineering, and underlying surface changes induced by other factors were the main causes of streamflow and sediment reduction.

Detecting the effects of climate changes and human activities on river regimes would help to identify the original driving forces of hydrological disturbances and highlight the mechanisms of such hydrological processes under changing conditions. Two non-parametric tests (Mann-Kendall and Pettitt) were applied to detect the change point of runoff (1964–2006) in the upper and middle reaches of the Heihe River basin. The change point was determined to be 1980, which divided the period into two parts (the baseline period and the change period). Double mass curve and hydrological sensitivity-based methods were used to separate the impacts of climate changes and human activities on runoff variation. The results demonstrated that human activities were the dominant force affecting runoff variation in the upper and middle reaches of the basin. At the sub-basin level, climate changes played a more significant role in the upstream region, while human activities dominated in the midstream region. Therefore, different countermeasures should be taken in the upstream and midstream regions to ensure sustainable water resource development in the Heihe River basin.

AT Marala barrage, two canals, i.e. Marala Ravi Link Canal (MRLC) and Upper Chenab Canal (UCC) off-take from left side of the River Chenab. MRLC has a very old history of experiencing sedimentation issues. Several attempts have been made to counterfoil or minimize this problem in the recent past. Two remarkable measures are the remodeling of MRLC in 2000–2001 (intervention-1) and the shifting of the confluence point of a heavily sediment-laden upstream tributary of the Chenab River by construction of a spur dike in 2004 (intervention-2). This paper investigates the effectiveness of these structural interventions as sedimentation control measures. The baseline period is selected from 1997 to 2000 and the impact is analyzed for two post-intervention time steps, i.e. evaluation period-1 ranging from 2001 to 2004 and evaluation period-2 from 2005 to 2011. Results obtained from double mass analysis revealed that sediment load increased by 33 and 8 % due to intervention-1, while decreased by 12 and 22 % due to intervention-2 in MRLC and UCC, respectively. The results suggest that monsoon floods are mainly responsible for sediment loading in the canals (66 % for UCC and 73 % for MRLC), supported by the finding that effective discharge (1900 m3 s−1) is almost twice the mean annual river discharge. The discharge classes between 900 and 2900 m3 s−1 are mainly responsible for major proportion (89 % in MRLC and 86 % in UCC) of the total sediment load over the 15-year study period. The intervention-1 could not minimize the sediment entry into the canals; rather it aggravated the situation. The intervention-2, however, proved a useful structural measure in this regard.

River sediment flux, the most critical element of land-ocean interaction, is undergoing significant changes due to climate variability and anthropogenic activities. Thus, identifying the driving forces and their contributions to the variation in sediment load is of great significance for sustainable management of soil and water resources. However, the dynamics behind these changes are not well understood, and the quantification of drivers of sediment load change remains scarce. In this study, we investigated the changes in hydrometeorological variables and quantitatively separated drivers of sediment load change in the Yangtze River (YZR) basin, China, during 1956–2015. The Mann-Kendall test and sequential cluster method were employed to examine the trends and abrupt changes in water discharge and sediment load. Results showed that the mean annual precipitation for most sub-basins and water discharge at most stations exhibited no apparent downward trend, while annual temperature showed a significant upward trend for most sub-basins. Sediment load decreased significantly at most stations, with breakpoints occurring around 1968 and in the early 2000s. The whole study period was split into three sub-periods (1956–1968, 1969–2002 and 2003–2015) to quantify the change in sediment load. As indicated by water-sediment relationships at 12 stations, the slope of the double mass curve showed a considerable decreasing trend during the period 2003–2015. A decomposition method based on sediment identity factor analysis was applied to quantify the impact of driving forces on the variation in sediment load. It was found that a decrease in suspended sediment concentration accounted for approximately 100–125% of the basin-wide reduction in sediment load in the YZR basin. Construction of large reservoirs played a dominant role in sharp decline in sediment load across the basin, which was responsible for about 157 Mt yr−1 and 384 Mt yr−1 of sedimentation for the period 1969–2002 and 2003–2015, respectively. Soil conservation projects played the secondary role in reducing sediment load, which led to an average decrease of 234 Mt yr−1 in the entire basin during 1989–2015. Hence, more attention should be paid to changes in sediment load resulting from increasing human activities in the future.

Climate change and human activities have been identified as the two main reasons for the change in runoff. To better understand the factors causing runoff change, this paper develops an integrated approach which combined the elasticity coefficient approach (including a non-parametric model and six Budyko framework based models) and the hydrological modelling approach (using SIMHYD models) for partitioning the impacts of climate change and human activities on surface runoff. The Guanzhong River Basin(GRB), which is the sub-basin of the Wei River basin in China is chosen as the study area. In this study, trends in runoff, rainfall and potential evapotranspiration (PET) from 1958 to 2008 are analyzed using the Mann-Kendall test and change-points in the annual runoff from 1958 to 2008 are sought using the Fu formula, Mann-Kendall test and double mass curve. The calibrated and validated rainfall-runoff model SIMHYD is used to simulate the runoff in the GRB during 1958–2008. Seven different methods are used to calculate the elasticity coefficient and then the elasticity coefficient methods are used to evaluate the contribution of climate change and human activities. Combining all these results, the contribution of climate change and human activities to runoff change is 34.1 ~ 47.3 and 52.7 ~ 65.9 %, respectively. The study provides scientific foundation for understanding the causes of water resources decrease and significant information for water resources management under the influence of climate change and human activities.