Abstract: The history of China's hydrological forecasting and technique progresses are reviewed in this paper,which involves the use of empirical correlations,catchment hydrological modeling,and the development of hydrological forecasting systems.The commonly used methods and models for hydrological forecasting are discussed in detail together with the conditions for applications.The current skill of China's hydrological forecasting techniques is assessed objectively.In-depth analysis of the impacts of intense human-induced land-surface changes and global warming on the catchment runoff generation and flow concentrating is provided.Emerging issues and challenges in hydrological forecasting under a changing environment is also analyzed.Finally,the future direction of China's hydrological forecasting development is prospected together with research focuses on the subject.
Abstract: The interaction of hydro-geomorphological processes is a nature phenomenon universally observed.Revealing of the quantitative relationship between the two processes is the long-term goal of hydrologists,which also is one of the important tasks listed in the new International Hydrological 10-year PUB(Predictions in Ungauged Basins). The paper discusses the basic ideas and the main characteristics of statistical synthetic methods,as well as physics-based methods that establish the quantitative relationship between the two processes.For more than a century,especially over the past 30 years,the geomorphology-based hydrological methods developed by international scholars are commented on.The author's contributions to the subject in recent years are also highlighted.
Abstract: The paper reviews and summaries the state-of-the-art,major progresses,and future perspectives in hydrological sciences.The study reveals that the societal need is the fundamental driving force and the advance in science and technology is the source for the development of hydrological sciences.In hydrological sciences,land surface hydrological processes should be investigated,as well as the water and energy exchanges among the atmosphere,land surface and groundwater.Physical processes of water transfer and movement should be investigated,as well as the chemical processes of different chemical compositions dissolved in the water.The study,in particular,the need for including the biological processes in hydrological cycle and water movement should be strengthened towards ecohydrology.At present,both ecohydrology and impact of climate change are very active in hydrological sciences under the changing environment.The theory of hydrological sciences should be further improved and developed.The socio-economic benefits of hydrological services should be enriched and strengthened in the future.Hydrological science could thus play an active role to support socio-economic development.
Abstract: This paper reviews the developmental milestones in China gauging station network.Using data from the 2005 China hydrological survey,the status quo of automation of hydrologic data collection and density of gauging station network is presented.An evaluation of gauging station networks is done for rivers with drainage areas greater than 500 km2.The current situation is objectively assessed for the monitoring of hydrological conditions using gauging station networks.The assessment is also done in comparison with situations in other countries,which can guide future improvements on the subject.
Abstract: The consensus since 1950s on the similarities and differences of hydrologic frequency distribution models is reviewed.The similarities and differences of statistical characteristics in these models are analyzed.Under the condition of having the same distribution of geometric shapes,the currently used models with only 3 parameters are essentially different.Observations and real case studies reveal that a unique solution might be existed if a 4-parameter model is considered.We have obtained a unique solution in model parameter estimation using mathematic methods.However,as discussed in the paper,most others first calculate the parameter CS value that is subjected to larger uncertainty and the CS value is then used in the calculation of other one or two parameters,which also contain larger uncertainty.As such,the results can only be taken as the initial estimation of model parameters.The rational analysis must be used to finalize the model parameters.
Abstract: As a part of the Chuzhou hydrological experimental system,the No.1 experimental catchment,Nandadish,with drainage area of 7 897 m2 sits on the andesite bedrock with Quaternary deposit of 2.46 m in average.Various runoff components,surface runoff and subsurface runoff including interflow from unsaturated zone,groundwater flow from saturated zone are physically measured using special designed troughs.Several combined types of runoff components are identified as the SR type with surface runoff dominated,SSR type with subsurface runoff dominated and other intermediate types.Examples show that surface runoff accounts for 65% of total runoff for SR type,while the subsurface runoff accounts for 90% in SSR type.In July,the main rainy season,in total,the subsurface runoff contributes an amount of 54.5% of total runoff while groundwater flow accounts for 33.0%.Most 18O data of surface runoff is quite different from that of precipitation.Within the rainfall-runoff process with duration of about 1 400 minutes,averaged 18O of precipitation is -1.210%,while that of surface runoff is -1.132% for Hydrohill catchment (512 m2),-1.065% for Nandadish catchment and -0.801% for Morningflower(4573 m2)which is a catchment with thin layer of rock debris on bedrock.It challenges the assumptions involved in current isotopic hydrograph separation,i.e.,the 18O of surface runoff will not always equal to that of event precipitation and,the evaporation fractionation during the pathway of runoff components could not always be ignored.Event rainfall produces runoff but such runoff contains an amount of water not from the event rainfall,such a paradox exists in all of our experimental catchments.The total old water involved in event runoff accounts for 16% for the SR type while 64% for SSR type.
Abstract: On the basis of identifying water problems at home and abroad,this paper analyses the evolution pattern of the natural-artificial dualistic water cycle,clarifies the interactions among hydrological processes,and associated hydrochemistry,water ecology and flow-sediment processes,as well as preliminarily describes the subject system constitution of modern hydrology and water resources.Based on describing the development trend of international hydrology and water resources and hot issues and frontier problems,and combining with research status of hydrology and water resources and practical demands on solving water problems in China,we discuss the subject system of hydrology and water resources in China,and analyze the important research directions.Under the influences of environmental change and strong human activities,water cycle shows obviously the natural-artificial characters on all aspects of dynamics,structure and parameters.Modern hydrology and water resources research is changing from traditional methodology of decomposition and refinement to present emphasis on integration and crossover,and from single-hydrological-variable oriented research to integrated hydrological processes oriented research.Prototype observation and numerical simulation become a critical study method in these fields.Hydrology and water resources research needs further strengthening on the basic research of mechanism identification and quantitative simulation of the water cycle and associated processes,improving on the application basic research of assessment,allocation and regulation of water resources,water right distribution,and water pricing theory and technology,to serve water-saving society establishment,water environmental protection and ecological construction,integrated water resources management,disaster prevention and mitigation and emergency treatment,drinking water safety,hydraulic engineering construction,and other practical needs.
Abstract: Research efforts were made to study several major issues in formulating the flood prevention plan of China's seven large river basins.The planning activity was organized by the Ministry of Water Resources.Our research recommendations were adopted during the course of the plan formulation.For example,we propose using the severe floods submerge areas of the 20th century as benchmarks for the identification of future flood prevention areas. Our viewpoint is that the most important consideration in the flood risk management is to actively circumvent risks and respond to risks.The core of circumvention risk is to restrict those unreasonable social economic activities of humankind,and thus reducing the flood risk.The design standard of a flood prevention area needs to be verified using a two-dimensional probability distribution method when the area is potentially threatened by two kinds of flood risks.Rationally upgrading the flood prevention standard is the priority in urban flood control.It is essential to better coordinate urban flood control and development,and to make full use of the urban damping effect on rainwater including retention of necessary water areas and utilization of rainwater.We should have well-balanced consideration to both options of storing and draining rainwater,rather than overemphasizing on the drainage option alone.We recommend that comparison and selection of safe development scheme for a flood retention area should comprehensively consider the risk zone that is divided using the integrated flood risk factor based upon the duration,frequency and depth of inundation, as well as the area natural and geographic conditions.
Abstract: The state-of-the-art review of joint operation for multi-reservoir systems in recent years is given.The basic operation rules,objective functions,optimization algorithms and applications of multi-reservoir systems are discussed and analyzed in detail.The future research on the multi-objective optimization technology,decision support system, optimal rules and allocation of benefits for joint operation of multi-reservoir systems are suggested.
Abstract: In order to analyze and assess the impact of climate change on regional hydrology and water resources, three indices including average annual precipitation,the trend index and Hurst coefficients reflecting the continuity of hydrology series are calculated on the bases of measured annual precipitation series in the east of China from 1956 to 2000,and then compared with those calculated on the bases of the simulated annual precipitation series from each of three climate models(CGCMA3,MPI-ECHAM5 and Average GCM).It is found that each index values between the observed and simulated series are different quantitatively and even contradictory qualitatively.This indicates that the uncertainty is significant in the application of models.Similarly,average annual runoff,the trend index and annual runoff of different drought years for the future annual runoff series from 2001 to 2050 also have significant uncertainty. Future annual runoff series is produced by using the predicted annual precipitation and temperature data from three climate models.Finally,some suggestions on climate models and its application are proposed in this study.
Abstract: The vertical distribution of suspended load concentration is one of the key theoretical components in sediment research.The vertical distribution of sediment concentration in non-equilibrium transportation is further studied using methods of theoretical derivation and numerical calculation in this article.A new concept of non-saturation sediment flux is proposed together with the derived mathematical expression.The theoretical solutions of vertical distribution of sediment concentration in non-equilibrium transportation are deduced,which include the exponential formula and power formula(Rouse formula),as well as the method of sediment concentration on bottom.At the same time, the two-dimensional diffusion equations on longitudinal section are resolved using the finite difference method.The arithmetical solutions of vertical distribution of sediment concentration in non-equilibrium transportation are worked out with different parameters,and coincident with the theoretical results from formulas except in a few cases with small errors.
Abstract: The variation tendency of runoff and sediment load in China major rivers is studied based on the representative hydrological stations of the rivers.The results show that there is no significant change in the mean annual runoff (1.409×1012 m3/a)of those stations;and little change is detected in the annual sediment load before 1960.However,the sediment load decreases gradually from 26.43×108 t/a in the 1950s to 5.95×108 t/a in the 2000s after 1960;and the corresponding change in the average sediment concentration is from 1.74 kg/m3 to 0.46kg/m3.Regionally,the annual runoff of major southern and inner rivers in China remains almost unchanged,a significant reduction in annual runoff is however detected in many representative hydrological stations of northern rivers except for the Huaihe and Songhua rivers.Varying degrees of reduction is found in the sediment load of China major rivers except for the Tarim River,and the greater reduction occurs in northern rivers.Human activities and natural factors are mainly responsible for the detected variations in runoff and sediment load,of which natural factors include changes in precipitation amounts and land covers over the river basins,and human activities factors refer to those measures in soil and water conservation,reservoir engineering,inter-basin water transfer projects,water diversion,sand excavation,and soon.
Abstract: The mechanism of river meandering is investigated experimentally based upon the principle of energy conservation.Our study reveals that meandering is a natural property of rivers.The curvatures of a river bend are largely controlled by the energy of river flow,i.e.,the flow rate and the channel slope.River meandering is a natural fluvial process to compensate the energy loss so that the river could keep itself moving forwards.The meandering channel process can result in a rise in the upstream water level,consequently increasing the potential energy in the channel reach and leading to a rising in the downstream channel slope as well as the kinetic energy increases.The latter,in turn,results in a relative equilibrium state between the flow and the sediment transport in the channel reach.The mechanism of river meandering may thus be rephrased as a river automatic regulating process.The degree of curvature in a channel reach is subject to the gained kinetic energy,i.e.,the difference in kinetic energy between upper-and downstream cross-sections determines the degree of river meandering.The automatic kinetic energy compensation in river reaches could be used as the mechanism to explaining river meandering.Such a mechanism is justified by the in-door experiments and field observation.
Abstract: A landslide lake is formed by watercourse blocking.It is a lake without any specialized designs as well as specific flood discharge facilities.If the dam was to burst,massive hazards would be posed.The experiences and cognition for emergency disposal of landslide lake are summarized.The formation cause,burst mechanism and landslide lake risk evaluation are analyzed.The disposal principle,concept,stage and approaches to addressing the issues are then brought forward.Taking the emergency disposal of landslide lakes due to the Wenchuan earthquake as an example,the disposal practice for the Tangjiashan landslide lake is introduced,including the dam burst mode,dam outburst flood,overall program for emergency risk mitigation,diversion channel scheme and risk elimination.Finally, other practices for emergency disposal of landslide lake are briefly introduced,which could give references on the subject.
Abstract: By modifying and integrating existing concepts and models for describing the structure and function of a river ecosystem,a holistic conceptual model is developed.The hydrological regime,flow conditions and geomorpho-logical patterns are three major habitat factors that have profound impacts on the structure and function of a river ecosystem.The central piece in a holistic conceptual model is to establishing the interrelationship between the life supporting system that is mainly driven by the three factors and the river life system.The human-induced variability of habitat factors and its effect on the river ecosystem are considered during the modeling process.A holistic conceptual model usually consists of four sub-models,which are the 4-dimensional river continuum model,the coupled hydrological regime and ecological process model,the suitability model integrating of hydraulic conditions and biological and life history traits,and the spatial heterogeneity of geomorphology and biocenoses diversity model.The integration of these four models can provide essential aspects of describing the structure and function of a river ecosystem.
Abstract: Through the concept of watershed ecological security from the point of view of river development and protection,a key ecological indicator system for water project planning and design is established by the model of the Driving forces-Pressure-State-Impact-Response(DPSIR).Five ecological attributes for the indicator system are proposed based on the analysis of structure and function of watershed ecosystem,which are hydrology and water resources,water environment,river geomorphology,biological species and habitat,and social environment.With the analysis on the main ecological elements of each attribute,these five ecological attributes are further subdivided into 19 ecological elements.Considering various scale effects and combined with the type and phase division of water project planning and design,the structure frame of the indicator system is established,and then totally 36 key ecological indicators for the indicator system are screened by expert consultancy and frequency analysis.The indicator system owns characteristics of multi-dimension and multi-level,and is applicable to different spatial scales and different stages of water project planning and design.It is significant for drafting or revising the standards of water projects planning and design in China.
Abstract: A model for defining environmental flow thresholds is developed using the abrupt habitat change analysis approach.The model takes into account the characteristics of aquatic ecosystems during spring flood periods,and uses the instream flow incremental methodology combined with the River2D model for fish habitat and the Mann-Kendall Method to establish the dynamic relation between the habitat and runoff.The model is tested on the data from the Wudaogou station located at the downstream of Huifa River.The data includes the streamflow velocities and water levels representing the habitat of the carp fish,as well as the monthly runoff of spring flood period from 1956 to 2000. The result of the Mann-Kendall analysis shows that the habitat of carp has undergone an abrupt change beginning in 1970.Prior to the abrupt change,the 95% confidence interval on the weighted usable area ranges from 275.5 to 915.7 m2/km,and the corresponding streamflow discharges taken as the environmental flow thresholds are from 58.8 to 121.1 m3/s.Spring flooding occurs after the icebound season,and the appropriate environmental flow of spring flood period is very important for the aquatic organisms and the entire ecosystem.
Abstract: China agricultural water use and management are facing enormous challenges in the 21st century.The core concepts of the paradigm shift in the global scientific research and public policy are regarding the agricultural water use and management in the last decade,i.e.,green water(GW),blue water(BW),the crop water productivity (CWP),and the broadly-defined agricultural water resources(BAWR),as well as matching between the cropland and the BAWR.Using these concepts,we propose an integrated framework for assessing China's agricultural water use of 1998-2007.The results reveal that among all the water that is potentially available for the cropland use,the GW contribution accounts for 57%and the remaining 43% are coming from BW.The CWP of major grain crops have already been at or approaching to the higher levels as measured by the international standards.Further improvement on the subject is thus limited.Based upon our estimated value of BAWR,the bottom line of water resources for the China's food security should then be set at 7 800×108m3.