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This paper explores whether the sponge city construction implemented in China can restore the hydrological condition of the river basins through runoff depth. The annual runoff depth was calculated based on the volume capture ratio of annual rainfall (VCRAR) and compared with undeveloped and before sponge city construction. The results conclude as follows: the current rainwater source control standard benefits the hydrology recovery in China. But the difference between before sponge city construction and undeveloped is large in 12.9% of the regions. The adjustment recommendations of the VCRAR proposed in this paper are favourable to restoring the river basin hydrology. [ABSTRACT FROM AUTHOR]

Climate change is the dominant factor affecting the hydrological process, it is of great significance to simulate and predict its influence on water resources management, socio-economic activities, and sustainable development in the future. In this paper, the Xiying River Basin was taken as the study area, China Atmospheric Assimilation Driven Data Set (CMADS) and observation data from the Jiutiaoling station were used to simulate runoff of the SWAT model and calibrate and verify model parameters. On this basis, runoff change of the basin under the future climate scenario of CMIP6 was predicted. Our research shows that: (1) The contribution rates of climate change and human activities to runoff increase of the Xiying River are 89.17% and 10.83%, respectively. Climate change is the most important factor affecting runoff change of the Xiying River. (2) In these three different emission scenarios of SSP1-2.6, SSP2-4.5 and SSP5-8.5 in CMIP6 climate model, the average temperature increased by 0.61, 1.09 and 1.74 °C, respectively, in the Xiying River Basin from 2017 to 2050. Average precipitation increased by 14.36, 66.88, and 142.73 mm, respectively, and runoff increased by 15, 24, and 35 million m³, respectively. The effect of climate change on runoff will continue to deepen in the future. [ABSTRACT FROM AUTHOR]

Urban stormwater management measures, such as permeable pavement systems (PPSs), have been widely implemented to alleviate increasingly severe urban water-related problems. However, the effectiveness of PPSs in runoff control under different rainfall conditions has not been fully investigated, particularly in China. Therefore, there is an urgent need to study the hydrological benefits of different PPSs in China. In this paper, five PPSs at the Zhenjiang sponge base, including one pervious concrete (PC), two permeable interlocking concrete pavements (PICP1 and PICP2), and two permeable bricks (PB1 and PB2), were selected as study cases. Surface runoff coefficients, underdrain runoff coefficients, total runoff volume reductions, and peak flow reductions during rainfall events throughout the flood seasons of 2019 and 2020 were calculated. The influence of rainfall characteristics, pavement type, and pavement age on PPS hydrological performance were evaluated by statistical analyses (p<0.05). The results revealed that the average values of surface runoff coefficients, underdrain runoff coefficients, total runoff volume reductions, and peak flow reductions by the PPSs were approximately 0.025, 0.003, 98.1%, and 96.4%, respectively, in 2019 and changed to 0.045, 0.001, 96.3%, and 92.4%, respectively, in 2020. PC performed best with regard to surface runoff control at the initial stage of operation, followed by PB and PICP. Both rainfall depth and rainfall intensity had a significant correlation with each hydrological performance metric. The increase in surface runoff generation from 2019 to 2020 mainly resulted from the clogging problem, which was closely related to pavement type and surroundings of PPSs. PB performed better than PC and PICP in terms of sustainable hydrological performance. The results provide a scientific reference for the design, construction, and operation of PPSs and can aid with the sustainable construction of sponge cities in China. This study evaluated the runoff reduction performance of five PPSs under natural rainfall events, which were observed during the flood seasons of 2019 and 2020 in Zhenjiang, Yangtze River Delta of China. In total, approximately 96% of the rainfall was captured by the PPSs during the monitoring period, and the PPSs performed better in lower-intensity rainfall events. However, the runoff reduction performance of the PPSs decreased markedly with operation time due to clogging, which is closely related to the pavement type and site surroundings of the PPS. To maintain the function of PPS for runoff control in a long period of time, the permeable brick system is the best type of PPS compared with PC systems and PICP systems. The results indicated that the application of PPSs in sponge city construction could be beneficial in the mitigation of urban floods, and adequate attention should be paid to the clogging problem of PPSs at every stage of PPS design, construction, and operation. [ABSTRACT FROM AUTHOR]

The land surface model (LSM) is extensively utilized to simulate terrestrial processes between land surface and atmosphere in the Earth system. Hydrology simulation is the key component of the model, which can directly reflect the capability of LSM. In this study, three offline LSM simulations were conducted over China using the Community Land Model version 5.0 (CLM5) driven by different meteorological forcing datasets, namely China Meteorological Forcing Dataset (CMFD), Global Soil Wetness Project Phase 3 (GSWP3), and bias-adjusted ERA5 reanalysis (WFDE5), respectively. Both gridded and in situ reference data, including evapotranspiration (ET), soil moisture (SM), and runoff, were employed to evaluate the performance levels of three CLM5-based simulations across China and its ten basins. In general, all simulations realistically replicate the magnitudes, spatial patterns, and seasonal cycles of ET over China when compared with remote-sensing-based ET observations. Among ten basins, Yellow River Basin (YRB) is the basin where simulations are the best, supported by the higher KGE value of 0.79. However, substantial biases occur in Northwest Rivers Basin (NWRB) with significant overestimation for CMFD and WFDE5 and underestimation for GSWP3. In addition, both grid-based or site-based evaluations of SM indicate that systematic wet biases exist in all three CLM5 simulations for shallower soil layer over nine basins of China. Comparatively, the performance levels in simulating SM for deeper soil layer are slightly better. Moreover, all three types of CLM5 simulate reasonable runoff spatial patterns, among which CMFD can capture more detailed information, but GSWP3 presents more comparable change trends of runoff when compared to the reference data. In summary, this study explored the capacity of CLM5 driven by different meteorological forcing data, and the assessment results may provide important insights for the future developments and applications of LSM. [ABSTRACT FROM AUTHOR]

This paper presents an evaluation of the spatio-temporal patterns of hydrologic alteration induced by dam construction and precipitation variability in the Lancang River Basin of southwest China from 1957 to 2000. Analyses were conducted using the linear regression method, the Mann-Kendall test, and the Range of Variability Approach. The results indicate that there was considerable variation in the average monthly precipitation between the pre- and post-dam periods in the Lancang River Basin. Second, the magnitude of monthly runoff was strongly related to precipitation, which showed an up-down annual variation, and was significantly altered by dam construction and precipitation variability. In the modified series (hydrologic series with the precipitation impacts removed), runoff deviations between the pre- and post-dam periods became larger. Third, the extreme runoff cycles were influenced by dam construction and precipitation variability downstream from the dam, and the monthly maximum runoff increased from the pre-dam to post-dam period at all hydrologic stations. Fourth, the degree of hydrologic alteration (DHA) indicates that the precipitation variability not only affected the hydrologic regime of unregulated river reach but also modified the negative impacts of dam construction, which could provide a modest mitigation of the hydrologic alterations induced by dam construction, possibly decreasing the level of DHA. Last, the overall degree of hydrologic alteration in the observed series reached 25.2, 25.3, and 29.1 % for the upstream, midstream, and downstream areas, respectively. These results show that the hydrologic regimes of the Lancang River during the 1957-2000 period were affected by damming and precipitation variability, but the hydrologic alteration was relatively low in the upstream areas of the river without a dam. [ABSTRACT FROM AUTHOR]

Long-term hydrologic prediction in ungauged basins is one of critical issues in the field of hydrologic calculations. Hydrologic analogy is an important method for long-term hydrologic prediction and hydrologic calculation in ungauged basins. The key point of hydrologic analogy is how to select a reference basin. This paper systematically discusses four popular methods to select a reference basin in China, which include grey analysis, fuzzy analysis, projection pursuit (PP), and set pair analysis. Through a case study in a small basin in Hebei Province, North China, the four methods are applied to select a reference basin. The advantages and disadvantages of these methods are explored. The results indicate that all four methods could be used in selecting a reference basin. It will depend on the familiarity and the experiences of the users with a specific method. [ABSTRACT FROM AUTHOR]

Abstract: Land use change has significant impacts on hydrologic processes at the watershed level. This paper combines an empirical land use change model and an event-scale, rainfall-runoff model to quantify the impacts of potential land use change on the storm-runoff generation in the Xitiaoxi basin upstream of Taihu Lake watershed. The HEC–HMS rainfall-runoff model is calibrated and validated for 7 storm events in the study area, and the results show good consistency between the simulated and measured hydrographs at the outlet of the basin with Nash–Sutcliff efficiency ranging from 75% to 95%. Then two future land use scenarios for the year 2050 are forecasted using the CLUE-s model based on the land use of 2002: (1) scenario A with an increase in urban area from 9.2% to 17% of the entire watershed and (2) scenario B with an increase from 9.2% to 14%. Finally, the calibrated HEC–HMS model is applied for these future land use scenarios under designed storms with different recurrence intervals to assess the potential land use impacts on the storm-runoff generation. The results indicate that the future land use scenarios are projected to increase the total runoff as well as the peak discharge, and that the magnitude of increment relates to the expansion rate of built-up area. In the case of rainstorms with recurrence intervals of 10, 50 and 100 years, the simulated peak discharges increase by 3.8%, 2.6% and 2.3% under scenario A, and by 2.8%, 1.9% and 1.7% under scenario B, respectively; while the total runoff is projected to increase by 4.7%, 3.4% and 3.0% under scenario A, and by 3.3%, 2.5% and 2.1% under scenario B. It can be concluded that the sensitivity of hydrologic response to land use change tends to increase as the recurrence interval of rainfall events decreases. Additionally, remarkable spatial variations of the land use changes and its impacts can be observed at the subbasin level, and the most sensitive subbasin is closeby the city. The results of this paper can provide useful support for land use planning and management, and the methods applied here have proved a useful tool for land use impact studies. [Copyright &y& Elsevier]

The paper examines the role of mountain runoff in the seasonal growth of oasis vegetation in the hyper-arid region of northwest China. Central to this examination is the development of a simple hydrologic model that relates hydrologic inflows and outflows estimated from remote sensing data (e.g., evapotranspiration, precipitation, snow accumulation, and snowmelt) to the calculation of runoff over a ten-year period (2000–2009). Modeled runoff is shown to reproduce the seasonal trends in hydrometric data fairly well, yielding R 2 's of 0.75 and 0.66 for stations in the upper reaches of the Shiyang and Hei River systems. Greater than 90% of the runoff from the Qilian Mountains to the oases occurs during the May–September period. Considerable discrepancy between modeled and observed runoff exists in the lower reaches of the rivers, where significant amounts of river water (>45%) are routinely extracted for cropland irrigation. Along the river systems, where water extraction and inflow of glacial meltwater are minor, model calculations replicate observed water yields much more closely. Analysis of seasonal trends in the contribution of snowmelt and rainfall to the return flow, reveals snowmelt as having the greatest influence in initiating the oasis growing period during the March-to-May period of each year. [ABSTRACT FROM AUTHOR]

Afforestation to control soil erosion has been implemented throughout China over the past few decades. The long‐term hydrological effects, such as total water yield and baseflow, of this large‐scale anthropogenic activity remain unclear. Using six decades of hydrologic observations and remote sensing data, we explore the hydrological responses to forest expansion in four basins with contrasting climates across China. No significant change in runoff was found for the period 1970–2012 for the cold and dry Hailar River Basin in northeastern China. However, both forest expansion and reduced precipitation contributed to the runoff reduction after afforestation since the late 1990s. Similarly, afforestation and drying climate since the mid‐1990s induced a significant decrease in runoff for the Weihe River Basin in semi‐arid northwestern China. In contrast, the two wet basins in the humid southern China, Ganjiang River Basin and Dongjiang River Basin, showed insignificant changes in total runoff during their study periods. However, the baseflow in the winter dry seasons in these two watersheds significantly increased since the 1950s. Our results highlight the long‐term variable effects of forest expansion and local climatic variability on basin hydrology in different climatic regions. This study suggests that landuse change in the humid study watersheds did not cause dramatic change in river flow and that region‐specific afforestation policy should be considered to deal with forestation‐water quantity trade‐off. Conclusions from this study can help improve decision‐making for ecological restoration policies and water resource management in China and other countries where intensive afforestation efforts are taking place. Key Points: Both precipitation and afforestation explained reduction in runoff for dry basinsForest recovery did not result in significant changes in total runoff for two wet basinsDry season baseflow in two wet basins had an upward trend [ABSTRACT FROM AUTHOR]

Climate change is one of the main factors that affect runoff changes. In the upstream of Minjiang River, the temperature increased significantly in the last 50 years, while the precipitation decreased on the contrary. In order to analyze the effect of climate change on site runoff, watershed runoff depth and evaporation, nine climate scenarios are assumed based on rainfall and temperature indicators. A SWAT model of Minjiang River is constructed, and runoff simulation is carried out with the nine scenarios. The results show that if precipitation increases or decreases 20 %, the change rate of runoff depth will increase or decrease 28-32 %; if temperature increases or decreases 2 °C, the change rate of runoff depth will decrease or increase 1-6 %; if temperature increases or decreases 2 °C, the change rate of the potential evaporation will increase or decrease 5-16 %, and the actual evaporation rate of variation will increase or decrease 1-6 %. Overall, precipitation variation has greater effect on simulated runoff than temperature variation dose. In addition, temperature variation has more obvious effect on the runoff simulation results in dry years than in wet years. The actual evaporation of watershed depends on evaporation capacity and precipitation and increases with the increasing of the potential evaporation and precipitation. The study also shows that the climate change scenarios analysis technology, combined with SWAT hydrological model, can effectively simulate the effect of climate change on runoff. [ABSTRACT FROM AUTHOR]

Summary: The hydrological cycle has been substantially influenced by climate change and human activities. It is therefore of utmost importance to analyze the impact of climate change on hydrology, particularly on a regional scale, in order to understand potential future changes of water resources and water-related disaster, and provide support for regional water management. However, during the evaluation of climate change impact on hydrology or water resources, large uncertainty exists. In this paper, the Soil Water Assessment Tool (SWAT) model is used to investigate the potential impact of climate change on hydrology of the upper reaches of Qiantang River Basin, East China, for the future period 2011–2100. The uncertainty is considered by employing upgraded reliability ensemble averaged GCM climate projections under three emission scenarios A1B, A2 and B1 for three different stages of the future period. These projections are downscaled and used in the hydrological model. Impact of climate change on precipitation, potential evapotranspiraton and river runoff is then investigated. The model calibration and validation outcomes show reasonable performance of the SWAT model. The final results suggest that annual river runoff will likely decrease almost under all emission scenarios and time stages of the future period. Particularly, at Jinhua Station, substantial decrease of annual river runoff can be noticed, indicating less water resource possibly available for the region in future. Simulated monthly patterns show that the largest decrease will likely occur in winter while increases will occur in summer, implying possible more water-related disasters in this region. However, it is also noticed that the change signs/amount could be different under different emission scenarios and time stages, indicating large uncertainty involved in the impact analysis. [ABSTRACT FROM AUTHOR]

Summary: This paper aims to provide an enhanced understanding of the parameter sensitivities of the Soil and Water Assessment Tool (SWAT) using a variance-based global sensitivity analysis, i.e., Sobol′’s method. The Yichun River Basin, China, is used as a case study, and the sensitivity of the SWAT parameters is analyzed under typical dry, normal and wet years, respectively. To reduce the number of model parameters, some spatial model parameters are grouped in terms of data availability and multipliers are then applied to parameter groups, reflecting spatial variation in the distributed SWAT model. The SWAT model performance is represented using two statistical metrics – Root Mean Square Error (RMSE) and Nash–Sutcliffe Efficiency (NSE) and two hydrological metrics – RunOff Coefficient Error (ROCE) and Slope of the Flow Duration Curve Error (SFDCE). The analysis reveals the individual effects of each parameter and its interactions with other parameters. Parameter interactions contribute to a significant portion of the variation in all metrics considered under moderate and wet years. In particular, the variation in the two hydrological metrics is dominated by the interactions, illustrating the necessity of choosing a global sensitivity analysis method that is able to consider interactions in the SWAT model identification process. In the dry year, however, the individual effects control the variation in the other three metrics except SFDCE. Further, the two statistical metrics fail to identify the SWAT parameters that control the flashiness (i.e., variability of mid-flows) and overall water balance. Overall, the results obtained from the global sensitivity analysis provide an in-depth understanding of the underlying hydrological processes under different metrics and climatic conditions in the case study catchment. [ABSTRACT FROM AUTHOR]

Variability and availability of water resources under changing environment in a regional scale have been hot topics in recent years, due to the vulnerability of water resources associated with social and economic development. In this paper, four subbasins in the Dongjiang basin with a significant land use change were selected as case study. Runoffs of the four subbasins were simulated using the SCS monthly model to identify the quantitative impacts of land use and climate change. The results showed that (1), in the Dongjiang basin, temperature increased significantly, evaporation and sunlight decreased strongly, while precipitation showed a nonsignificant increase; (2) since the 1980s, land uses in the Dongjiang basin have experienced a significant change with a prominent increase inurbanareas, amoderate increase in farmlands, anda greatdecrease inforest areas; (3) the SCSmonthlymodel performed well in the four subbasins giving that the more significant land use change in each subbasin, the more runoff change correspondingly; (4) overall, runoff change was contributed half and half by climate change and human activities, respectively, in all the subbasins, in which about 20%~30% change was contributed by land use change. [ABSTRACT FROM AUTHOR]

Abstract: Characterizing the landscape changes and hydrologic alterations associated with dam construction is very important for watershed management. This paper presents a case study of the Lancang River in Yunnan Province following dam construction. The landscape patterns and dynamics indicate the fragmentation, shape, and diversity of the river in 1980, 1990, and 2000. The Range of Variability Approach (RVA) is used to evaluate the degree of hydrologic alteration (DHA) using 44 years (1957–2000) of hydrologic data. The results indicate that the midstream and downstream landscapes were affected by dam construction, becoming more complex and fragmented during the 1980–2000 period; the upstream area was not influenced by dam construction and the reservoir impoundment exhibited less change. The variability in maximum runoff occurrence in the post-dam period was less than that in the pre-dam period. The integrated DHAs of the Jiuzhou (upstream), Gajiu (midstream), and Yunjinghong (downstream) stations were relatively low, reaching 26.28%, 33.40%, and 37.14%, respectively. However, the alteration became obvious in the midstream area, and the situation worsened when the river was simultaneously influenced by dam construction and other human activities (downstream). The results of the regression analysis show strong relationships of landscape metric changes with DHA, and the forestland and water areas with DHA. The DHA increased along with the aggravation of landscape fragmentation, the complexity of the landscape shape, and the diversification of the landscape. [Copyright &y& Elsevier]

Using tree-ring data of Pinus sylvestris var. mongolica from the Hulun Buir region in northeast China, 12 annual runoff series of the Hailar River spanning the past 202-216 years were established for the first time; these included 11 branches and one for the entire basin. These reconstructions, which could explain 29.4%-52.7% of the total variance for the measured runoffs during 1956-2006, performed well in statistical verification tests. In the whole basin's reconstruction of 212 years, 34 extreme drought years (16.0%) and 41 extreme pluvial years (19.3%) were identified; 4 of the 10 most extreme years occurred after 1980. The consistent cycle and correlation revealed that the Hailar runoff had a teleconnection with the El Niño-Southern Oscillation (ENSO). The sharply increasing variance at the end of the reconstruction, accompanied by the increasing intensity of short cycles (4-8 years), indicated that runoff variability in the Hailar River basin has enhanced in the late twentieth century. This is verified by the drastic fluctuations in water level and area of rivers and lakes, and the frequent shift of natural land cover types in the Hulun Buir area in recent decades. The intensified runoff variability can be connected with the concurrently enhanced ENSO activity. Our study is the first to identify the intensification of recent runoff variability in the semiarid to arid region in northeast China from a long-term perspective. With projected enhancement of ENSO activity, the Hailar River basin will face the increased risk of extreme hydrological events. [ABSTRACT FROM AUTHOR]

This study examined hydrological and meteorological changes in China's Nenjiang River Basin. Taking account of the physical processes in hydrology and meteorology revealed by the hydrological elements, we selected typical periods and sites for analysis on temperature (1951–2004), precipitation, and runoff data (1955–2005). Through some methods including improved cumulative curve method, the Sen slope estimation method, Mann-Kendall non-parametric test analysis, the Pettitt mutation point test and Spearman rank correlation test, and the spatiotemporal characteristics of hydrological and meteorological elements were evaluated. An innovative concept of the "centroid of precipitation" was proposed to analyze the spatial evolution tendency of precipitation. The results are concluded as follows: (1) the temperature began to show a rising trend during the 1960s and 1970s in Nenjiang River Basin in the twentieth century. The temperature had risen significantly by the 1990s. Furthermore, the temperature increased significantly at the coldest place and in the coldest month. (2) There was no significant trend change in the annual precipitation in the Nenjiang River Basin. However, monthly precipitation before the flood season (April) and after the flood season (October) exhibited a significant upward trend. The centroid of precipitation was concentrated in a compact spatial distribution in the main flood season but was dispersed relatively in the other months. (3) River runoff showed a downward trend year by year and exhibited a mutation in 1979. The spatial variation in runoff showed that the fluctuation of downstream runoff was greater than that in the upper reaches of the basin and that the runoff from the upstream to the downstream reaches gradually decreased. According to the M-K mutation point test, the Pettitt mutation point test, and the improved cumulative curve method, a mutation in annual runoff sequence occurred in 1979. These findings will be helpful for understanding evolution of hydrological changes and will be supportive for local water managers to deal with changing climate. [ABSTRACT FROM AUTHOR]

Much attention has been focused on investigating the effects of precipitation and temperature changes on runoff; however, the influence of wind speed, relative humidity and total solar radiation on hydrological components needs to be studied further. Hydrological responses to climate variations in a minimally disturbed mountainous watershed in the period 1971–2012 are identified and evaluated by statistical analysis and hydrological simulation. The results indicate that the impact of climate component changes on the hydrological process cannot be discounted. The temperature and relative humidity exhibit significant upward trends, while the wind speed exhibits a clear downward trend. The potential and actual evapotranspiration dramatically increased, but the observed pan evaporation substantially decreased. The surface water, soil water, baseflow and water yield are positively correlated with precipitation and relative humidity but negatively correlated with the temperature, wind speed and solar radiation. [ABSTRACT FROM AUTHOR]

Understanding the variability in soil hydraulic conductivity in the mountainous headwaters is critical to the modeling of mountainous runoff and the water resources management of river basins, especially in the arid and semiarid areas. In this study, a total of 32 soil profiles with five layers within 0-70 cm were sampled under different land cover types: forest, meadow, high coverage grassland (HCG), medium coverage grassland (MCG), and barren land in the upper stream of the Heihe river watershed, Northwest China. Saturated hydraulic conductivity ( KS) was measured for each sample. The vertical variation of KS and soil hydrological response under different land covers were analyzed. Results show that KS value in layer 5 was significantly lower than the values of above four layers. KS decreased in the order of forest, meadow, HCG, MCG, and barren land, corresponding to the degree of vegetation degradation. The KS decreased with depth under forest, HCG, and barren land, but increased first and then decreased under meadow and MCG. The dominant stormflow paths for different land covers were different: forest was dominated by deep percolation, HCG was dominated by subsurface flow (SSF), meadow was prevailed by Hortonian overland flow and had no SSF, while MCG and barren land were also dominated by Hortonian overland flow, but still formed SSF. This result provides important information for improving the accuracy of mountainous hydrological modeling and, in turn, leading to sustainable management of water resources in the study watershed. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Understanding the mechanisms of river runoff variation is important for the effective management of water resources in arid and semi-arid regions. This study uses long-term observational data as a basis for examining the effects of human activities and climate change on the runoff variation of Jinghe River Basin, a typical arid inland basin in northwest China. A distributed hydrological model called the Soil and Water Assessment Tool, combined with a sequential cluster method and a separation approach, was used to quantify and distinguish the effects of human activities and climate change on runoff. The hydrological sequence before 1981 can be considered natural. However, human activities have significantly affected runoff since 1981. The runoff reduction caused by human activities between 1981 and 2008 accounted for 85.7% of the total reduction in the downstream of Jinghe River, whereas that caused by climatic variation was only 14.3%. This observation suggests that human activities are the major driver of runoff variation in the basin. Although the role of climate change in driving runoff variation has been identified to be prevalent and dominant in arid regions, this study highlights the importance of human activities. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This study explores the teleconnection of two climatic patterns, namely the El Niño-Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD), with hydrological processes over the Pearl River basin in southern China, particularly on a sub-basin-scale basis. The Variable Infiltration Capacity (VIC) model is used to simulate the daily hydrological processes over the basin for the study period 1952-2000, and then, using the simulation results, the time series of the monthly runoff and soil moisture anomalies for its ten sub-basins are aggregated. Wavelet analysis is performed to explore the variability properties of these time series at 49 timescales ranging from 2 months to 9 yr. Use of the wavelet coherence and rank correlation method reveals that the dominant variabilities of the time series of runoff and soil moisture are basically correlated with IOD. The influences of ENSO on the terrestrial hydrological processes are mainly found in the eastern sub-basins. The teleconnections between climatic patterns and hydrological variability also serve as a reference for inferences on the occurrence of extreme hydrological events (e.g., floods and droughts). [ABSTRACT FROM AUTHOR]

Climate change has become an environmental issue of utmost importance, and one that will challenge existing water resource management practices in many ways. The Huaihe River, one of China's major rivers, is frequently subject to flooding and drought and, for the purposes of assessing the implications of climate change on water resources in the Huaihe River Basin, the variable infiltration capacity (VIC) model with a resolution of was calibrated using data from 11 well-gauged subbasins. The model parameters from the well-gauged stations were then transferred to poorly gauged areas according to similarities in, for example, climate conditions and soil texture. The calibrated VIC model was subsequently used to study the potential impacts of three climate change scenarios on basin runoff, taking projected runoff for 1961-1990 as the baseline. In general, the results showed that although the annual runoff will likely increase across the basin under the different scenarios, regional flooding and regional shortage in water resources will be exacerbated under the impacts of global warming. [ABSTRACT FROM AUTHOR]

Land-use change has significant impacts on hydrologic processes at the watershed level; thus, quantitative assessment on the impacts of land-use change is vital for basin environment protection and water resources sustainable development. Owing largely to computer and geographical information system (GIS) technology improvements, the distributed hydrological models, which allow describing the temporal variability and spatial distribution of water-balance components, offer an effective approach to quantify the land-use change effects on watershed water quantity. In this study, a soil and water assessment tool model was used to simulate land-use change effects on water quantity in the upper Huaihe River basin in China above the Xixian hydrological controlling station with a catchment area of by the use of temporal three-phase (1980s, 1990s, 2000s) land-use maps, soil type map (1:200,000 scale), and 1980-2008 daily time series of rainfall from the upper Huaihe River basin. Within the model, potential evapotranspiration was computed using the Penman-Monteith method coupled with a simplified plant growth model. On the basis of the simulated time series of daily runoff, land-use change effects on spatio-temporal change patterns of runoff coefficients and runoff modules, the rainfall-runoff relationship, the sensitivity of rainfall-runoff relationship to rainfall for different types of land use, and impact of land-use patterns on rainfall-runoff relationships were investigated. The results revealed that under the same condition of soil texture and terrain slope, the advantage for runoff generation and the sensitivity of rainfall-runoff relationship to rainfall decreased by farmland, paddy field, and woodland. With the same rainfall, the advantage for runoff generation increased by the 1990s, 2000s, and 1980s land-use patterns. The outputs could provide important references for soil and water conservation and river health protection in the upper stream reach of the Huaihe River. [ABSTRACT FROM AUTHOR]

Runoff in major rivers in China has been decreasing in recent decades. The attribution of hydrologic variability to human activity or climate change is a challenging problem and an active research area. In this study, a sequential cluster analysis method was used to detect undisturbed parts of the record for the Kuyehe River catchment in China. The variable infiltration capacity (VIC) land-surface model was calibrated and verified using observed hydrometeorological data from a period with relatively little human-induced disturbance. The calibrated VIC model was then used to simulate natural runoff during the human-regulated period. Results indicate that the recorded runoff at Wenjiachuan station had significant decline trend of . Time series of runoff was detected and divided into three epochs at two critical years of 1980 and 1998. The VIC model performed well in simulating monthly discharges in the catchment, both Nash and Sutcliffe efficiency (NSE) critera in calibration (1955 to 1969) and verification (1970 to 1979) were above 70% while relative errors (REs) were less than 5%. Human activity was the main driver behind 68% of the runoff reduction that occurred for the period of 1980 to 2008. [ABSTRACT FROM AUTHOR]

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Hydrologic alteration can be attributed to climate and human effects with some confidence. However, when quantifying the hydrologic alteration induced by dams using historical flow records, there is a lack of consideration concerning the impacts of climate variability on hydrologic alteration. Evaluating dam-induced and climate-influence-induced hydrologic alteration has emerged as a key problem, which is the process of quantifying the extent that they have altered the river's hydrologic attributes. Central to this process is restoring the hydrologic attributes without dam influence. This study simulates hydrologic regimes without dam influence and evaluates the dam and climate influences on hydrologic processes in the Lancang-Mekong River. The results showed that the meteorological variables were closely related with runoff. Therefore, a stepwise-regression model was established and validated using meteorological variables with their time lags, and it showed good performance. The simulative evaluation revealed that runoff from the Lancang River was simultaneously and significantly affected by dam construction and climate variability, and the damming effects were mainly concentrated in the primary stage of reservoir operation. Meanwhile, the dam operation increased the minimum and maximum monthly runoff over a year. During the study period, the degree of hydrologic alteration (DHA) indicated that the Manwan Dam compensated for the impacts of climate variability on the Lancang River. [ABSTRACT FROM AUTHOR]

The hydrological cycle in a catchment is sensitive to climate and land-use changes. The authors conducted a case study to validate the performance of the soil and water assessment tool (SWAT) and its applicability as a simulator of runoff and sediment transport processes at the mesoscale scale in arid and semiarid areas. SWAT is used to simulate runoff and sediment changes caused by human activities in a typical watershed, the Jihe Watershed (), in the Loess Plateau of northwestern China. A marked increase in temperature was observed over the analysis period. The investigation was conducted using 47 years of historical rainfall/runoff data and sedimentary records from 1962-2008. The data from 1962-1981 was used for calibration and that from 1982-2008 for validation. The results showed that the Nash-Sutcliffe model efficiency coefficient was approximately 0.7, the relative error was less than 15%, and the coefficient of determination was greater than 0.7, both for annual flow and sediment yield in the calibration period. These findings indicate that the SWAT model was able to simulate runoff and sediment yield satisfactorily; however, it exhibited better performance for the calibration period than for the validation period. Similarly, simulations of monthly flow and sediment were better for the calibration period. The simulated and observed values agree well with trend changes. Uncertainty analysis indicates that digital elevation model resolutions and watershed subdivisions imposed little influence on annual flow, but notable effects were observed with respect to annual sediment yield. [ABSTRACT FROM AUTHOR]

Climatic variability and human activities are the two primary factors that affect basin hydrology, and thus quantification of their effects is of great importance for water resources management and sustainable development at a catchment scale. In this study, the writers investigated the long-term trends and abrupt changes in hydroclimatic variables, including precipitation, potential evapotranspiration (PET), and runoff, from 1957-2000 in the Hutuo River Basin by the nonparametric Mann-Kendall test and the precipitation-runoff double cumulative curve method. A two-parameter hydrological model and linear regression method were employed to separate and quantify the effects of climatic variability and human activities on runoff. The results are the following: (1) significant downward trends for annual precipitation and annual runoff were detected by the Mann-Kendall test at a 99% confidence level, (2) a change in the gradient of precipitation-runoff double cumulative curves and an abrupt change in runoff series can both be found in 1979, indicating that the relationship between precipitation and runoff has changed; as a result, the annual runoff from 1957-2000 can be divided into two periods termed the baseline (1957-1979) and human-induced (1980-2000) periods, and (3) the climate variability was the primary cause for the decrease in annual runoff from the baseline to the human-induced period, despite certain effects of human activities on the change with respect to annual runoff. [ABSTRACT FROM AUTHOR]

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The article presents a study on the shift trend and step changes for runoff time series in the Shiyang River basin in northwest China. It states that seven statistical test approaches were used to determine the shift trends and step changes in the study. It discusses that Mann-Kendall test, Spearman's Rho test, linear regression and Hurst exponent were utilized to detect past and future shift trends for runoff time series, while the distributed-free CUSUM test, cumulative deviations and the Worsley likelihood ratio test were employed to detect step changes for the same time series. Results showed that the annual runoff from Zamu, Huangyang and Gulang rivers demonstrate statistically significant decreasing trends.

The article presents a study which focuses on the improvement of the peak flow rate equation used in the Chemicals, Runoff, and Erosion from Agricultural Management Systems (CREAMS) model, to be used in the Loess Plateau in China. The significance of the measure of the peak flow rates in CREAMS in soil conservation plans and engineering projects are discussed. The methods and results of the study and observations are also discussed. The new equation for the peak flow rate in CREAMS is also presented.

To simulate daily runoff in the middle and lower regions of the Changjiang (Yangtze River) basin, we used an integrated, spatially distributed model consisting of the Hydrological Simulation Program—FORTRAN (HSPF) and two newly developed submodels, the paddy runoff model (PRM), simulating the runoff from paddy fields, and the lake discharge model (LDM), simulating the hydraulic effect of the Changjiang mainstream on the discharge from neighboring lakes. In the PRM, the ratios of the simulated monthly evapotranspiration relative to the observed potential evaporation were close to or exceeded 1.0 in both of the test subcatchments in the full ponding period with plentiful irrigation water, corresponding to many previous observations of evapotranspiraion rates from paddy fields. Whereas the original HSPF could not consider the backwater effect of the water level in the mainstream, the daily discharge from the lakes simulated by the LDM was dependent on the water level in the mainstream and corresponded to the observed data at the hydrologic stations on the channels connecting each lake with the mainstream, as shown by the daily R2 (Nash–Sutcliffe coefficient) values for Dongting Lake (0.89 in the calibration period, 0.90 in the verification period) and for Poyang Lake (0.84 in the calibration period). For the runoff response from the whole basin simulated by the integrated model, the deviations of runoff volume and values of R2 were -4.2% and 0.95 in the calibration and verification periods and 1.6% and 0.93, respectively, at Datong hydrologic station, which shows the good applicability of this model as a tool for management of water resources in the Changjiang basin. [ABSTRACT FROM AUTHOR]

This study evaluates the performance of four evapotranspiration methods (Priestley-Taylor, Penman-Monteith, Hargreaves and Makkink) of differing complexity in a semiarid environment in north China. The results are compared to observed water vapour fluxes derived from eddy flux measurements. The analysis became necessary after discharge simulations using an automatically calibrated version of the Soil and Water Assessment Tool (SWAT) failed to reproduce runoff measurements. Although the study area receives most of the annual rainfall during the vegetation period, high temperatures can cause water scarcity. We investigate which evapotranspiration method is most suitable for this environment and whether the model performance of SWAT can be improved with the most adequate evapotranspiration method. The evapotranspiration models were tested in two consecutive years with different rainfall amounts. In general, the simple Hargreaves and Makkink equations outmatch the more complex Priestley-Taylor and Penman-Monteith methods, although their performance depended on water availability. Effects on the quality of SWAT runoff simulations, however, remained minor. Although evapotranspiration is an important process in the hydrology of this steppe environment, our analysis indicates that other driving factors still need to be identified to improve SWAT simulations. [ABSTRACT FROM AUTHOR]

With the change of climate and the impacts of human activities, the water resources crisis of the Yellow River is becoming increasingly serious. How and why did the streamflows of the Yellow River basin change? Based on observed annual runoff data (1956–2016) of 10 main hydrological stations along the Yellow River, the linear regression method, the Spearman rank correlation method and the Mann-Kendall test method are used to analyze runoff trend. The orderly clustering method, the sliding t test method and the Lee-Heghinian Method are used to identify the abrupt change point. Finally, the wavelet analysis method is used to identify runoff time series period. The results show that: (1) With the exception of the streamflow of Tangnaihai, the streamflows of all examined stations have significantly declining trends. The decrease of the streamflow from the upper to the middle to the lower reaches is becoming more and more obvious; (2) The runoff of the Yellow River has changed greatly. The abrupt change point at Tangnaihai occurred in 1989. The abrupt change points of the other stations took place in 1985; (3) The runoff along the Yellow River presents multi-time scale changes. The streamflows appear to have strongest periods of 25–40 years with a 40-year scale, which indicate the alternate oscillations of the high and the low water periods. The periods of <6 and 7–24 years are not stable and are complicated. The first main period of runoff in the Yellow River is 30 years; (4) The streamflow upstream of Tangnaihai station is mainly affected by the climate. The streamflows downstream of Tangnaihai station are influenced by human activities, especially water extraction and diversion and the operations of the large reservoirs. These research results have important practical guiding significance for hydrological forecasting, evaluation and management of water resources, construction of water conservancy projects and sustainable utilization of water resources in the region. [ABSTRACT FROM AUTHOR]