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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

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.

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

Homogeneous time series of meteorological variables are necessary for hydrologic and climate studies. Dependability of historical precipitation data is subjected to keen evaluation prior to every study in water resources, hydrology, and climate change fields. This study aims to characterize the homogeneity of long-term Turkish precipitation data in order to ensure that they can be reliably used. The homogeneity of monthly precipitation data set was tested using the standard normal homogeneity test, Buishand test, Von Neumann ratio test, and Pettitt test at the 5% significance level across Turkey. Our precipitation records including the most updated observations, extracted from 160 meteorological stations, for the periods 1974–2014 were analyzed by all the four homogeneity tests. According to the results of all tests, five out of 160 stations have an inhomogeneity. With regard to our strict confirmation rule, 44 out of 160 stations are said to be inhomogeneous since they failed from at least one of the four tests. The breaks captured by the Buishand and Pettitt tests usually tend to appear in the middle of the precipitation series, whereas the ability of standard normal homogeneity test is in favor of identifying inhomogeneities mostly at the beginning or at the end of the records. Our results showed that 42 out of 44 inhomogeneous stations passed all the four tests after applying a correction procedure based on the double mass curve analysis. Available metadata was used to interpret the detected inhomogeneity.

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.

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.

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.

The spatiotemporal patterns prevailing at regional scale can be significantly different from the patterns observed at basin or country scale. The present study aims to analyse regional-scale trends (spatial and temporal) in monthly, seasonal and annual time series, and change point in annual time series of temperature (Tmax, Tmean and Tmin), rainfall, runoff and evapotranspiration in Kesinga sub-catchment of Mahanadi basin over the period 1970–2015. Non-parametric Mann–Kendall (MK) test and Sen’s slope test have been applied to assess the significance and magnitude of the trends, respectively. In the results, increasing trends are observed in Tmax, whereas, Tmean- and Tmin are following insignificant decreasing trend. Rainfall exhibits significant increasing trend in monsoon and annual time series, whereas, insignificant decreasing trend prevails in post-monsoon and winter season. On the contrary, significant increasing trends are observed in runoff at the catchment outlet and evapotranspiration in all the seasons. The change point in annual rainfall and runoff as identified using non-parametric Pettitt test is found to be in the year 2000 which is further verified using sequential MK test. The significant change in LULC of the region from forest, swamp and fallow land to cropland over time has been found to be the possible reason for the breakpoint observed in double mass curve and discrepancies in the trend of rainfall and runoff during non-monsoon season. Overall, the influence of climate variability is mainly evident in annual and monsoon series, whereas, the effect of anthropogenic variables is confined to non-monsoon seasons.

The inter-seasonal behaviour of rainfall in the Soutpansberg region of South Africa was assessed in relation to changing climate with an attempt to diagnose some of the contributing external factors. Seasonal rainfall data from 1970 to 2009 was characterised for the Soutpansberg using 23 rainfall stations distributed over the mountain range. The normality of rainfall data was quality-controlled using the Pearson correlation coefficient and a double mass curve. Composite rainfall and standardised anomaly index for the region were calculated in order to assess seasonal variability of rainfall. The results showed that the range experienced a decline in seasonal rainfall, from east to west. The North West (NW) part of the region experienced its lowest rainfall in 1985, with a standardised anomaly index (SAI) of −0.94, and its highest rainfall was experienced in 1978, with an SAI of 0.5. The North East (NE) recorded lowest rainfall in 1985 with an SAI of −1, and the highest rainfall was observed in the years ranging from 1977 to 1980 with an SAI of 1. The South East (SE) experienced lowest rainfall in 1985 with a value of −1.25 below the mean, and its highest rainfall (1.25) was experienced in 1976. The study showed that seasonal rainfall in the north-facing slope was lower than the rainfall in the south-facing slope. Trend line analysis indicated that the NW part of the Soutpansberg experienced the most substantial decrease in rainfall. The NW region was followed by the NE, SW, SE and the Central East (CE) respectively in terms of the decline in rainfall. Such behaviour and trends which varies across space and time is a cause for concern in the period of study. This period was characterised by increase in anthropogenic activities, as earlier studies prior to 1970 demonstrated a near stable pattern in terms of the cyclic activity of rainfall.

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.

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.

Annual runoff in Luanhe river basin was detected a downward trend and caused water crisis in Tianjin, China. To quantify the decreased runoff volume, Mann–Kendall test and Pettitt test were employed to check whether there existed significant trend and change points for annual rainfall and runoff time series in Panjiakou reservoir basin and 8 sub-watersheds. It was found that the annual runoff time series had a significant downward trend at 5 % confidence level, and the change point was at 1979 in Panjiakou reservoir watershed. Then double mass curve of annual rainfall and annual runoff was plotted, and two lines were fitted before and after 1979, respectively. Based on this method, the comprehensive effects of land use/land cover change on annual runoff were estimated. To further quantify the contributions of each main factor to annual runoff decrease, water stored in check dams and social water use in different periods were surveyed first. And then multi-linear regression was used to develop the relations between annual runoff and the driven factors. Water area decrease was identified to be the main factor contributing to annual runoff reduction. The results in this study can provide valuable information for water resources planners and policy makers.

Building performance simulation is increasingly used to aid in decision making about the design, construction, retrofit, operation, and maintenance of new and existing buildings. Such simulations require a complete set of meteorological data sampled at regular intervals. A data file with even a single missing measurement value becomes useless for simulation. Unfortunately, it is extremely rare to find such a perfect body of data. Measurement errors and sensor failure are frequent occurrences in meteorological data collection and are among a host of reasons for missing measurement values. To overcome this problem, simulation users may rely on Typical Meteorological Years (TMYs) instead of actual historical data, or they may apply an existing interpolation method to fill the gaps in historical data. Historical data is often preferable, since TMYs fail to account for atypical weather conditions. Clearly, this could lead to poor decision making when the decision outcomes are strongly affected by the occurrence of atypical conditions. This paper presents several methods for statistical interpolation between discrete weather-data points. A normalization procedure is first used to transform meteorological data into a set of Gaussian-distributed sample data. Next, a vector autoregressive model is calibrated using the normalized site-specific meteorological data, and is then used to determine the most likely value for one or more missing data points. Variations of the model are described to address specific combinations of missing data, and the methods are validated for several cities in the USA. Results show that the normalization procedure is the most important contributor towards a significant improvement in accuracy relative to other interpolation methods.

In western Victoria, Australia the water table and lake level in the Glenelg-Hopkins catchment have been declining for the last 15 years, and this is attributed to either the low rainfall over this time and/or a substantial change in land use. Stream flow modelling was carried out using monthly empirical water balance model (modified tanh function together with double mass curve analysis), on 37 stream gauges to assess whether the impact of land use change could be detected by a change in the magnitude of the resulting runoff. The empirical hydrological model was able to distinguish impact of land use change on stream flow from the climatic variables. There were substantial decreases in stream flow in the 1970s–1980s, probably related to increasing livestock densities in the region. Furthermore, the methodology can be a powerful tool to monitor and evaluate the possible impacts of future land use changes. It can be concluded that the use of such empirical hydrological modelling greatly improves the ability to analyse the impact of land use on catchment runoff. The model is a practical tool that can be readily used for identifying and quantifying the effect of landuse changes on catchment for water resource decision-making, which could be hardly possible using the time consuming, data hungry and expensive physical process models available.

The Songhua River plays a key role in the national development of China, owing to its unique natural condition and resources. Recent changes in the streamflow in the Songhua River are important with regard to local sustainable development and management under the background of global warming and aggravating soil erosion. In order to detect changes in the streamflow, two streamflow series from 1955 to 2004 (observed at the Harbin and Jiamusi stations) in the mainstream of Songhua River basin were obtained, and methods of statistical analysis, wavelet transform, and double mass analysis were employed to analyze the data. Reasons for the changes to the streamflow are discussed with respect to natural and man-made drivers. The results show the following: (1) From 1955 to 2004, the streamflow series present obvious declining trends. (2) The streamflow series followed the pattern of a wet–dry–wet–dry cycle pattern over the past 50 years. In the mainstream of Songhua River, wet years mainly occurred during the periods of 1955–1966 and 1984–1993, while dry years mainly occurred in the 1970s and after 2000. (3) Within the 50-year scale, the streamflow series appeared in the main periods of circa 33-, 13- and 4-year, in which the 33-year periodicity is the strongest. (4) Precipitation and temperature directly influenced the streamflow in the mainstream of the basin. The discharge was positively correlated with the precipitation and negatively correlated with the temperature. In addition, human activity was another important driving factor for streamflow change. (5) In the mainstream of Songhua River basin, the influences on streamflow can be divided into three periods: 1955–1976, 1977–1997, and 1998–2004. In the first period climate change played a dominant role, and during the latter two periods human influences were enhanced significantly.

Groundwater abstraction has resulted in spring flow and groundwater base-flow declines in the Hillsborough River system of central Florida, USA. These declines have resulted in reduction of inflows to the Tampa city reservoir as well as likely adverse environmental effects on riverine and estuarine biota. Causes evaluated for the declines include effects of groundwater development, reduced rainfall, and land alterations. The karstic, heterogeneic nature of the area renders groundwater flow modeling an ineffective method for overall evaluation. Therefore, the evaluation of these declines is accomplished through the systematic use of parametric and nonparametric statistical techniques. These techniques include contingency table analysis, linear regression, Kendall-Theil and Mann-Kendall trend analysis, locally weighted regression, Pearson correlation, Kendall-tau correlation, Spearman correlation, runs test, Student’s t test, and the Kruskall-Wallis test. Data evaluated include groundwater withdrawals, rainfall, base flow, streamflow, stream stage, spring flow, and groundwater levels. Additional methods used include double mass analysis, base flow separation, a low-stage trend analysis, data visualization techniques, and water level change maps. The methodical application of these analyses and techniques to the hydrologic and climatic data yields the conclusion that the primary factor causing the spring flow and base-flow declines is lowered groundwater levels caused by over-abstraction.

In this paper, the average annual rainfall and runoff presented fluctuation trends in Three Gorges Reservoir Area was studied. To assess impact of forest coverage changes on runoff in Three Gorges Reservoir Area accurately, we selected rainfall time series, runoff time series and forest coverage rate as the research objects from 1955 to 2011 in Three Gorges Reservoir Area. In this study, we borrow the methods of Mann-Kendall time series trend analysis and double mass curve to quantitatively evaluate the response of runoff on forest coverage and the results showed that the average annual rainfall and runoff presented fluctuation have the trends, Rainfall and runoff average values were 1161.8mm, 38.58 billion m3 respectively, amplitudes were 744.0mm, 43.89 billion m3, and coefficients of variation were 13.4%, 26.1% from 1955 to 2011 in Three Gorges Reservoir Area. The results shows that the reservoir area runoff have four stages, the first one is that the reservoir area runoff had the same decreasing trend as precipitation before 1965. the second one is that annual runoff was from a decreasing trend to increasing trend, and achieved a significant increasing trend in 1983–2002.. the third one is that the extent of an upward trend began to decrease from 2003, and became a decreasing trend by 2011. the last one is that forest coverage changes have experienced from a small reduction to a substantial increase in Three Gorges Reservoir Area from 1950 to the present. When the forest coverage was low level ( 24%), increasing forest reduced river runoff.