Showing papers in "Hydrological Sciences Journal-journal Des Sciences Hydrologiques in 1999"

Prediction uncertainty of conceptual rainfall-runoff models caused by problems in identifying model parameters and structure

Abstract: The uncertainties arising from the problem of identifying a representative model structure and model parameters in a conceptual rainfall-runoff model were investigated. A conceptual model, the HBV model, was applied to the mountainous Brugga basin (39.9 km”) in the Black Forest, southwestern Germany. In a first step, a Monte Carlo procedure with randomly generated parameter sets was used for calibration. For a ten-year calibration period, different parameter sets resulted in an equally good correspondence between observed and simulated runoff. A few parameters were well defined (i.e. best parameter values were within small ranges), but for most parameters good simulations were found with values varying over wide ranges. In a second step, model variants with different numbers of elevation and landuse zones and various runoff generation conceptualizations were tested. In some cases, representation of more spatial variability gave better simulations in terms of discharge. However, good results could...

GR3J: a daily watershed model with three free parameters

Abstract: This paper describes a new empirical watershed model, the prime feature of which is its parsimony. It involves only three free parameters, a characteristic unparalleled by continuous process models able to work on a wide array of catchments. In spite of its crude simplicity, it achieved, on average, worthwhile results on a set of 140 French catchments and overwhelmingly outperformed a linear model involving 16 parameters. It performed roughly as well as a conceptual model with five free parameters, derived from the well-known TOPMODEL.

Flood protection and management: quo vadimus?

Abstract: In the last decade, there have been many destructive floods in various parts of the world. Despite the extensive investment in flood control works, neither flood occurrences nor damages are decreasing. A possible consequence of climate change is an increased frequency of extreme meteorological events that may cause floods. Discussion is offered of some recent large floods in the world and of the experiences in combating floods in Japan. Floods change over time as societies change. There is no single universal remedy against floods and site-specific local efforts are necessary. It is essential to undertake damage mitigation measures together with physical control measures for flood management in an integrated approach, using a mixture of structural and non-structural means. A more disaster conscious society needs to be built with better preparedness and safe-fail (safe in failure) rather than, unrealistic, fail-safe (safe from failure) design of flood defences.

Applying soft computing approaches to river level forecasting

Abstract: This paper assesses one of many potential enhancements to conventional flood forecasting that can be achieved through the use of soft computing technologies. A methodology is outlined in which the forecasting data set is split into subsets before training with a series of neural networks. These networks are then recombined via a rule-based fuzzy logic model that has been optimized using a genetic algorithm. The methodology is demonstrated using historical time series data from the Ouse River catchment in northern England. The model forecasts are assessed on global performance statistics and on a more specific flood-related evaluation measure, and they are compared to benchmarks from a statistical model and naive predictions. The overall results indicate that this methodology may provide a well performing, low-cost solution, which may be readily integrated into existing operational flood forecasting and warning systems.

Introduction of block-wise use of TOPMODEL and Muskingum-Cunge method for the hydro-environmental simulation of a large ungauged basin

Abstract: For the sustainable management of water quantity and quality, a hydrological model that can simulate the hydro-environmental dynamics of river basins at arbitrary locations is valuable. There are several streamflow simulation models suitable for such a purpose. Yet the lack of data commonly poses a serious problem for their application. This is a serious problem encountered for the sustainable management of water resources at a basin scale. This paper describes a combination of TOPMODEL with the Muskingum-Cunge flow routing method to overcome the problem at least partially. The resultant block-wise version of TOPMODEL is used to simulate daily flows in the data-rich 3570 km2 Fuji-kawa basin, central Honshu, Japan and in the data-poor 20 750 km2 northern part of Minjiang basin above Dujiangyan, Sichuan Province, China. The results demonstrate the potential use of the model for hydro-environmental simulation in a large data-poor basin.

The classification of hydrologically homogeneous regions

Abstract: With the operation and maintenance of streamgauging networks in many developing countries coming under increasing pressure through lack of funds and suitably trained personnel, greater reliance must be placed on procedures for transferring information from gauged to ungauged catchment areas. These approaches to generalizing hydrological variables, such as the quantiles of the frequency distributions of floods and low flows, are collectively referred to as regionalization methods. An important feature of these methods is the demarcation of hydrologically homogeneous regions. The latter may be regarded as an example of the wider problem of classification of data sets, for which a variety of modern informatic tools, such as artificial neural networks and fuzzy sets, may be invoked. Application of examples of these techniques to flood data for the southwest of England and Wales has demonstrated that classes may be defined by Representative Regional Catchments (RRCs), whose characteristics are hydrolo...

The Great Flood of 1997 in Poland

Abstract: The flood that occurred in summer 1997 in Poland, affecting the drainage basins of the Odra and the Vistula, caused 54 fatalities and material losses of the order of billions of US$. The flood struck a large part of the country and caused inundation of 665 000 ha of land. The number of evacuees was 162 thousand. The rhetoric commonly used in Poland refers to the Great Flood of 1997 as an event whose scale exceeded all imagination about the possible size of the disaster. Indeed, historic maxima of river stage and flow rate were considerably exceeded. From the hydrological point of view, this flood was a very rare event, with a return period in some river cross-sections of the order of a thousand years and more. As this natural disaster, striking a dynamically developing country-in-transition, attracted much international interest, a holistic view of it is presented. Attempts to answer the questions: “Could the disaster have been avoided?” and “What lessons can be learnt from the flood?” are also made.

Linking streamflow drought to the occurrence of atmospheric circulation patterns

Abstract: The growing use of surface water resources calls for more intense research on low flow causes and characteristics. This paper presents an investigation linking regional streamflow drought to the occurrence of atmospheric circulation patterns (CPs). Streamflow drought events of 74 basins in southern Germany were determined using the threshold level approach. The regional classification of the basins through a cluster analysis of the drought series provided the basis for the definition of a regional drought index and the following investigation of the influence of CP occurrence on drought. Frequency cross-tabulation showed several high-pressure and anticyclonic CP types to be strongly associated with streamflow drought in southern Germany. The influence of these CPs on streamflow drought was quantified using a logistic regression model. The model results revealed important regional differences concerning the time lag of the drought response and the relevant CPs.

Modelling river discharge for large drainage basins: from lumped to distributed approach

Abstract: The paper presents an upscaled application of the HBV model to the German part of the Elbe drainage basin, and intercomparison of lumped and distributed versions of the model. The objectives of the work were (a) to check the model performance for large-scale basins, and (b) to compare the lumped and distributed versions of the model. Three versions of the HBV model, one lumped and two distributed, were applied first to a number of sub-basins of the Elbe with different hydrological regimes (area > 1000 km2), and then to the whole German part of the basin (area 80 657 km2). The model performed well in all cases. The distributed model versions are more data intensive but enabled better results to be achieved. The perspectives for using the model for large-scale water quality assessment, for climate change impact studies and for coupled land-atmosphere modelling are discussed.

A comparative study of rainfall erosivity estimation for southern Italy and southeastern Australia

Abstract: In this paper, using Sicilian and Australian rainfall intensity data, a comparison between different estimators (modified Fournier index F, FF index) of the rainfall erosivity factor in the USLE was made. The relationship between the modified Fournier index and the mean annual rainfall, P, was theoretically derived. The K constant, linking the FF index and P, and its cumulative distribution function (CDF) were used to establish hydrological similitude among different geographical regions of southern Italy and southeastern Australia. To predict the erosion risk for an event of given average recurrence interval, the probability distribution of the annual value F a.j of the Arnoldus index was studied. In order to establish the theoretical CDF to use as a regional parent distribution, the descriptive ability of LN2 and EV1 distributions was studied by both an at-site analysis and a hierarchical regional procedure. The analysis showed that for each sub-region of southern Italy and southeastern Austral...

Drying out of small prairie wetlands after conversion of their catchments from cultivation to permanent brome grass

Abstract: Water level data have been collected since 1968 for small wetlands within a 385 ha area in the northern prairie region of Canada. The uplands around the wetlands were under dryland cultivation prior to 1968 and there was no significant change of land use until 1980. Between 1980 and 1983 about one-third of the area was converted to a permanent undisturbed cover of smooth brome grass (Bromus inermis) and some alfalfa (Medicago saliva) with the purpose of providing improved bird nesting habitat. The remainder of the area continued in cultivation. Wetlands within the grassed area dried out within a few years after conversion of their catchments to permanent brome grass, whereas wetlands in the neighbouring cultivated area retained water as before. Within the area of permanent grass cover springtime snowmelt runoff essentially ceased. These observations demonstrate that the water balance of prairie wetlands is very sensitive to the land use on the surrounding uplands.

Automatic calibration of groundwater models using global optimization techniques

Abstract: The problem of a groundwater model calibration is posed as a multi- extremum (global) optimization problem, rather than the more widely considered single-extremum (local) optimization problem. Several algorithms of randomized search incorporated in the global optimization tool GLOBE are considered (including the canonical genetic algorithm and more recently developed adaptive cluster covering), and applied to the calibration of the groundwater model TRIWACO. The results show the usefulness of global optimization algorithms in the automatic calibration of even complex models having considerable running times. Calage automatique de modeles d'ecoulement souterrain utilisant des techniques d'optimisation globales Resume Par opposition a l'approche classique qui considere le probleme du calage des modeles d'ecoulement souterrain comme un probleme d'optimisation a un extremum (optimisation locale), nous posons ce probleme ici en termes d'optimisation a extremums multiples (optimisation globale, OG). L'application de divers algorithmes de recherche aleatoire (recherche aleatoire controlee, algorithme genetique canonique et couverture adaptative) au modele d'ecoulement souterrain TRIWACO montre l'interet de l'utilisation des algorithmes OG pour le calage de modeles qui, en raison de leur complexite, exigent des temps de calcul considerables.

Flood protection—sustainability Issues

Abstract: There has been much recent emphasis on sustainable development of water resources in that the needs of the present generation are fulfilled without compromising future generations to meet their needs. Also, systems of flood protection and management are being increasingly considered in the context of sustainable development. Destructive floods have jeopardized settlements located near rivers since the dawn of human history. Now, the global flood losses have grown worldwide to the level of billions of US dollars per year. The issue of climate variability and change and the possibility of their adverse impacts on the severity and frequency of flooding, introduces an additional uncertainty to difficult sustainability issues. There are several examples of technical infrastructure related to flood protection, which are being criticized in the context of sustainable development because they close options for future generations and introduce unacceptable disturbances in ecosystems. Large structural floo...

Climate change and sustainable water resources: placing the threat of global warming in perspective

Abstract: Predicted climate change over the coming decades is likely to add measurable stress to water resources in many regions of the world, including some areas that are currently well endowed. The stresses are likely to involve changes in the frequency of extreme events as well as gradual changes in mean annual net resources. The paper analyses these predictions. It also attempts to place them in context, first, comparing their impact with other major barriers to sustainability, such as increasing demand, wastage, poor water resources assessment and international conflict, and, secondly, considering the limitations of current predictive techniques.

A real-time combination method for the outputs of different rainfall-runoff models

Abstract: Application of the concept of combining the estimated forecast output of different rainfall-runoff models to yield an overall combined estimated output in the context of real-time river flow forecasting is explored. A Real-Time Model Output Combination Method (RTMOCM) is developed, based on the structure of the Linear Transfer Function Model (LTFM) and utilizing the concept of the Weighted Average Method (WAM) for model output combination. A multiple-input single-output form of the LTFM is utilized in the RTMOCM. This form of the LTFM model uses synchronously the daily simulation-mode model-estimated discharge time series of the rainfall-runoff models selected for combination, its inherent updating structure being used for providing updated combined discharge forecasts. The RTMOCM is applied to the daily data of five catchments, using the simulation-mode estimated discharges of three selected rainfall-runoff models, comprising one conceptual model (Soil Moisture Accounting and Routing Procedure—S...

Rainfall distribution function for Libya and rainfall prediction

Abstract: Monthly rainfall amounts are distributed according to different frequency distribution functions in different parts of the world. However, in extremely arid regions gamma probability distribution functions are most often found to fit the existing data well. Libyan monthly rainfall distributions are found to abide by gamma probability distribution function which is confirmed on the basis of chi-square tests. Almost all the rainfall sequences recorded for at least the last 20 years in Libya are investigated statistically and gamma distribution parameters are calculated at existing stations. The shape and scale parameters are then regionalized and hence it becomes possible to find the parameter values at any desired location within the study area and then to generate synthetic sequences according to the gamma distribution. Predictions of 10, 25, 50 and 100 mm rainfall amounts are achieved by this probability function.

Monitoring the propagation of a debris flow along a torrent

Abstract: The results are presented of a field experiment on debris flow monitoring that were obtained in the summer of 1996 in a small mountain torrent in the Italian Alps. A network of seismic detectors was placed about one kilometre upstream of some previously existing gauging stations equipped with ultrasonic devices. In June and July two debris flows occurred, which were recorded both by the seismic and the ultrasonic sensors allowing a comparison between the two results. For the first event, the plot of the mean velocity of ground vibration vs time revealed a strong similarity with the hydrograph recorded at the gauging sites: the graphs show the passage of a debris flow wave with a sharp peak followed by subsequent smaller waves. An estimation of the mean front velocity of these waves was performed at both sites.

Water circulation in karst and determination of catchment areas: example of the River Zrmanja

Abstract: Karst hydrological investigation of the sinking stream problem of the River Zrmanja is presented. The aim of this analysis is to assess the feasibility of constructing three hydroelectric power plants (HEPP) along the River Zrmanja course. This paper presents a suitable and simple hydrological methodology that can be applied to scarce available data obtained on complex karst terranes. The paper presents a complex but common case of water circulation in a karst system. The primary objectives of the investigations were: (a) to analyse the underground karst connections, (b) to analyse discharge conditions along the River Zrmanja, and (c) to define variations in the catchment area along the River Zrmanja. The fact that the hydrological regime of the River Zrmanja is highly variable, due to the water losses along the open streamflow, strongly influenced the selection of the locations and heights of the HEPP dams. In spite of many hydrological, meteorological and hydrogeological measurements, the River...

A multi-objective fuzzy pattern recognition model for assessing groundwater vulnerability based on the DRASTIC system

Abstract: More and more problems with groundwater come from the increasing industrialization and the growing waste problem. The DRASTIC model has been used as a valuable tool in many parts of the world for assessing the vulnerability of groundwater. In the DRASTIC system, however, factors that influence groundwater must be divided into ranges and then be given ratings according to whether or not their values can be directly measured. The system may give the same range and rating to those having obviously different values. As a result, DRASTIC may be unable to actually reflect the difference between factors and hydrogeological settings. In fact, there exists a transition from the easiest to be polluted to the most difficult to be polluted so that vulnerability of groundwater is of a fuzzy nature and therefore fuzzy sets theory can be used to assess the vulnerability of groundwater. In this paper, a multi-objective fuzzy pattern recognition model for assessing the pollution potential of groundwater is presen...

Dimensionality of Scandinavian river flow regimes

Abstract: A river flow regime describes an average seasonal behaviour of river flow, usually representing a set of long-term monthly mean values. Seasonal patterns of flow can be regular, repeating in principle the same pattern from year to year, or irregular, i.e. alternating between a couple of different regime types during individual years. By tradition, a river flow regime has been considered as a static characteristic that does not change in large temporal scale, yet this may be an oversimplification with regard to constantly changing environmental conditions. Such a "static" description of a flow regime, based on long-term mean values is in discrepancy with the dynamic character of the system described. The dimension of this system in terms of fractal and intrinsic dimensions has been investigated on an example of Scandinavian runoff series by different methods: from a simple graphic method to determine the fractal dimension to empirical orthogonal function (EOF) and entropy-based aggregation to outline the number of patterns necessary for representing the regimes of different intrinsic dimension of a set of point data. The series studied demonstrated a variety of fractal and intrinsic dimensions that were well in agreement with the stability character of the investigated regime types. The less stable the regime, the higher were its fractal and intrinsic dimensions and the number of variables required for its description. Structure dimensionnelle des regimes d'ecoulements des rivieres

Facing the challenge: barriers to sustainable water resources development in China

Abstract: This paper addresses the water resources management problems in China. Considering the pressure of increasing population, present barriers to alleviation of floods, droughts and water environmental problems have been carefully analysed from the Chinese practical background. The discussions involve water resources and problems in managing water supply and demand in China. Due to very uneven distribution of precipitation in space and time, China frequently suffers from floods and droughts. But the coincidence of the rainy season with the warm season is favourable to crop production and thus results in high population density in the eastern part of China. In order to avert disastrous consequences of hydrological extremes—floods and droughts now and in the future—studying sustainable development of water resources in China is an imperative. Based on results of such studies, existing barriers to sustainable development of water resources have to be removed. A number of feasible measures adaptable to t...

Simplified mass balance models for assessing soil erosion rates on cultivated land using caesium-137 measurements

Abstract: Soil erosion on agricultural land has become a global environmental problem and information on rates of soil loss is an important requirement both for quantifying the problem and for developing improved land management and soil conservation practices. The use of fallout 137Cs measurements overcomes many of the difficulties facing traditional approaches to erosion monitoring and affords an effective means for obtaining estimates of soil redistribution rates on cultivated land. A number of empirical functions and theoretical models have been developed to establish the relationship between the change in the soil 137Cs inventory relative to the local 137Cs fallout input and the rate of soil redistribution. Of these approaches, physically-based mass balance models have received increasing emphasis, but their application may be hampered by their complexity and the need to specify values for a number of parameters. This paper presents a refined simplified point-based mass balance model for deriving esti...

Fuzzy optimal model for the flood control system of the upper and middle reaches of the Yangtze River

Abstract: Based on the characteristics of the Yangtze River floods and the principles of fuzzy sets theory, a fuzzy optimal model has been established for the flood system of the upper and middle reaches of this river. The system is divided into three subsystems with specific flood control objectives. The Three-Gorges Reservoir plays an important role in the system. A method for producing flood operation alternatives of the Three-Gorges Reservoir is presented. Finally, the model is validated with three typical historical floods. The results show that the model is effective and flexible.

Assessment criteria for simple conceptual daily rainfall-runoff models

Abstract: Four simple conceptual daily rainfall-runoff models are applied to a 25-basin data set. The drainage basins are all from the UK, covering a range of sizes, topographies, soils and climates. The quality of the simulation of the observed response is classically quantified by a minimized objective function. However, in this instance, model performance is judged by a range of quantitative and qualitative measures of fit, applied to both the calibration and validation periods. These include efficiency, mean annual runoff, baseflow index, the synthetic monthly and daily flow regimes, and the flow duration curve. The main conclusion is that the quantitative criteria used alone are rarely sufficient to determine the quality of the model performance. It is usually necessary to include some qualitative indication of goodness-of-fit, such as the quality of the synthetic daily flow hydrograph. However, assessment of the quality of daily flow regimes can be highly subjective.

Using a stochastic model for generating hourly hyetographs to study extreme rainfalls

Abstract: A stochastic model for generating hourly hyetographs has been developed using data from observed precipitation records to simulate rainfall patterns. This model makes it possible to study maximum precipitation distributions for normal or exceptional frequencies over long periods of time. The modelling provides observations (up to 10-year frequency) of quantiles similar to those observed by directly fitting a law of statistical distribution onto an observed distribution. Differences occur for rare frequency quantiles. Modelled rainfall frequency distributions behave in an over-exponential way (i.e. greater than strictly exponential) at infinity, yielding higher results than those obtained using standard fittings. One factor that is considered in modelling can explain this behaviour: the persistence of storms within a rainfall episode which causes high rainfall accumulation. Thus modelling the observed phenomenon provides an innovative approach in studying extreme occurrences.

Hydrological modelling of a drained grazing marsh under agricultural land use and the simulation of restoration management scenarios

Abstract: The capability of the spatially-distributed, physically-based, rainfall-runoff modelling system, MIKE SHE, to simulate the hydrological behaviour of the natural and drained parts of the North Kent Grazing Marshes, UK, is investigated. The MIKE SHE code is applied to Bells Creek, a small, underdrained, agricultural catchment located within the marshes. The model is used to both provide insights into the essential parameters that control the hydrological processes in the catchment, and predict the influence of various, hypothetical, water management strategies (land use and drainage) on pumped discharge and soil moisture storage in the catchment. The water table model predictions arising from these hypothetical scenarios are also compared against field data obtained from on-going hydrological research on the neighbouring, natural, Elmley Marshes. The comparison is found to be favourable. The results of this study indicate the potential of the MIKE SHE system to simulate the hydrological regime of t...

Application of principal components analysis to the study of CO2-rich thermomineral waters in the aquifer system of Alto Guadalentín (Spain)

Abstract: Le sud-est des Cordilleres Betiques a ete longtemps reconnu comme une zone possedant de nombreuses anomalies geothermales regionales. Beaucoup de sources thermales apparaissent liees a des systemes de failles tectoniquement actifs. Le dioxyde de carbone et d'autres gaz sont mobilises dans ces eaux a travers des systemes de failles. La grande profondeur de ces zones de decrochement affecte toute l'epaisseur de la lithosphere, ce qui permet de distinguer deux domaines corticaux de nature et structure differentes. Dans cette zone, l'aquifere detritique de l'Alto Guadalentin a des eaux thermales de haute salinite et des teneurs en CO 2 sous forme gazeuse anormalement elevees. L'utilisation de l'Analyse en Composantes Principales (ACP) dans l'etude hydrogeochimique de cet aquifere a revele que l'origine de la salinite de ses eaux est essentiellement due aux processus de dissolution des roches evaporitiques miocenes, principalement de sulfates, et a la contribution d'eaux hydrothermales profondes qui montrent des signes de contamination endogene par le CO 2 . Dans une moindre mesure, les eaux d'infiltration constituent un apport de teneur elevee en sulfates, chlorures et nitrates. L'ACP a de plus permis de differenciet plusieurs groupes d'eaux, selon la contribution de ces divers processus.

Flood-induced embankment failures on the River Tay: implications of climatically induced hydrological change in Scotland

Abstract: Agricultural flood embankment failure frequency within the Tay drainage basin in Scotland is explored by examination of breach data (228 breaches in total) collected during an eight-year period in which a large number of high discharge flood events (with return periods of up to 120 years) occurred. The data illustrates that overtopping is the main mechanism of failure, that certain reaches and specific locations are particularly vulnerable to failure, and that a near-linear increase in number and total length of flood embankment failures occurs with percentage increase in flood peak discharge. Non-hydrological factors contributing to flood embankment instability include construction over former river channels, location on the outside of meander bends and “honeycombing” of embankments as a result of rabbit burrowing. Hydrological data suggests an increase in the frequency of high magnitude flood events since 1988 in the drainage basin and an identifiable spatial variability; catchments draining mo...

Particle size characteristics of suspended sediments and subglacial hydrology of Dokriani Glacier, Garhwal Himalaya, India

Abstract: Diurnal and seasonal variations in particle size characteristics of suspended sediments of Dokriani glacier meltwater were studied during the 1994 ablation period (May-October). Diurnal suspended sediment concentration curves exhibit two prominent peaks from May to mid-August and only one peak during the rest of the ablation period. The first peak resulting from dominance of fine and medium sand contributed to the rising limb of the diurnal hydrograph, whereas the second peak was dominated by fine and medium silt which coincides with the diurnal discharge peak. The trends observed on the appearance of silts and sand particles on diurnal scales at various stages of the ablation period suggest that the subglacial drainage system comprises a diurnally-reversing hydraulic gradient between the channels and distributed system along with translatory flow through the distributed system. This study suggests that the subglacial zone is the major source of sediments in the Dokriani glacier meltwaters. Howev...

TwoLe: a software tool for planning and management of water reservoir networks

Abstract: A software tool, which implements a Decision Support System (DSS) for management of water reservoirs, is presented It is designed to be used both at the planning level, by water agencies, to generate management policies and release plans over various time horizons, and at the management level, by the decision makers, to take daily release decisions, also using the real-time information provided by a telemetering network The DSS algorithm presents multiple choices to the decision makers, helping them in assessing their impact, thus integrating, not substituting, human intelligence The DSS architecture relies on a Model Management System (MMS) to allow a rapid prototyping of various modelling situations, both at the planning level and at the management level, while the graphical user interface is aimed at enforcing this structure