To address the challenge of obtaining reliable streamflow data for water resource management, thi... more To address the challenge of obtaining reliable streamflow data for water resource management, this paper develops an encoding scheme to transform a streamflow time series into an 8-bit grayscale image where it is feasible to develop a correlation between neighbouring pixels to reveal patterns that are not easily discernable in traditional time series analysis. To extract relevant information from an encoded streamflow image, a novel textural feature extraction approach has been developed for synthesizing streamflow data. The developed textural feature extraction model can capture the simultaneous correlation in two dimensions of an encoded streamflow image, which is then transformed into the frequency domain using a discrete Fourier transform. The use of the power spectrum of the Fourier coefficients facilitates the synthesis of encoded streamflow images. The effectiveness of the model is evaluated using three case studies across Canada by comparing the properties of synthesized str...
Daily streamflows; Mutual information; Embedding dimension; Hurst coefficient Summary The existen... more Daily streamflows; Mutual information; Embedding dimension; Hurst coefficient Summary The existence of outliers in data sets affects the decision-making process related to design, operation, and management of water resources. Insufficient informa- tion on outliers limits our understanding and predictive ability of such extreme hydrologic phenomena. Hydrologic systems are complex and dynamic in nature where current state and future evolutions depend
Among the various methods for estimating reservoir volumes, the Gould probability matrix (GPM) me... more Among the various methods for estimating reservoir volumes, the Gould probability matrix (GPM) method has been touted as a powerful method for estimating reservoir volumes. The other methods in vogue are the Behavior analysis (BA) with the latest induction of the Drought magnitude (DM) method. A comparison of the above methods in terms of ease, efficiency, and relative merits from each other is currently lacking in the literature. This paper compares the above three methods with a detailed analysis of the GPM method using the monthly flows from 16 Canadian rivers at the draft ratios of 75 and 50% with the probability of failure of 2.5, 5 and 10%. The results reported in this paper indicate that fifteen zones are sufficient in the GPM method to yield the reservoir capacity for the Canadian rivers while requiring no standardization of the data, similar to the BA method. In the DM method, standardized monthly flow sequences in combination with a scaling parameter Φ yielded effective dr...
... 4. Significance of neural networks in monthly streamflow data. Monthly streamflows are often ... more ... 4. Significance of neural networks in monthly streamflow data. Monthly streamflows are often short and exhibit a nonlinear multi-variable nature and this can make it ... ANN models have been applied to solve problems concerning missing data and data forecasting in hydrology ...
Uniqueness of the problem surrounding non-detects has been a concern alike to researchers and sta... more Uniqueness of the problem surrounding non-detects has been a concern alike to researchers and statisticians dealing with summary statistics while analyzing censored data. To incorporate non-detects in the estimation process, a simple substitution by the MDL (method detection limit) and the maximum likelihood estimation method are routinely implemented as standard methods by US-EPA laboratories. In situations where numerical standards are set at or near the MDL by regulatory agencies, it is prudent and important to closely investigate both the variability in test measurements and the estimation bias, because an inference based on biased estimates could entail significant liabilities. Variability is understood to be not only inevitable but also an inherent and integral part of any chemical analysis or test. In situations where regulatory agencies fail to account for the inherently present variability of test measurements, there is a need for regulated facilities to seek remedial action merely as a consequence of inadequate statistical procedure. This paper utilizes a mathematical approach to derive the bias functions and resulting bias curves are developed to investigate the censored samples from a variety of probability distributions such as normal, log-normal, gamma, and Gumbel distributions. Finally, the bias functions and bias curves are also compared to the results obtained by using Monte Carlo simulations.
Page 1. This article was downloaded by: [66.249.68.69] On: 08 July 2011, At: 00:43 Publisher: Tay... more Page 1. This article was downloaded by: [66.249.68.69] On: 08 July 2011, At: 00:43 Publisher: Taylor & Francis Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK ...
Preferential accumulation of minerals with high densities forming placer deposits in longitudinal... more Preferential accumulation of minerals with high densities forming placer deposits in longitudinal bars of braided rivers relies on the segregation of this denser material from the quartz and feldspar sands dominating sediment in transport. Flume experimentation conducted on mixtures of quartz, pyroxene, magnetite, and lead sand transported over rough cobble beds demonstrated that the sand distribution was more uniform above the bed than theory predicted. The deviation from theory was inversely proportional to the density of the mineral. Fall velocity was not a good predictor of the amount of a mineral species carried in suspension, as coarsegrained quartz dominated the suspension population in the flume runs where lead was a major constituent in the traction population, even though the quartz had a greater fall velocity. Applying these results to placer deposits indicates that during flood events, even the smaller dense minerals and especially the super-dense minerals will be transported with the gravel and cobble load, whereas the quartz and feldspar will be spatially segregated during transport and temporally and spatially segregated during deposition. This mechanism of placer formation is capable of creating the types of deposits present in orebodies and showings such as the uraniferous paleoplacers at Elliot Lake, Canada, and the gold-bearing longitudinal bars in the Witwatersrand.
Computer models are no longer viewed as exotic luxuries, rather they are being increasingly accep... more Computer models are no longer viewed as exotic luxuries, rather they are being increasingly accepted as necessities for effective planning and operation of water distribution systems. In large networks, pressure-reducing valves (PRVs) are common water appurtenances. However, through the use of the Hazen–Williams friction factor, there are difficulties in representing PRVs in network-analysis models. This paper focuses on these difficulties and suggests a procedure for resolving them through the use of modified Hazen–Williams friction factor. The effectiveness of the proposed modification in representing PRVs in the WATER model is demonstrated. Key words: network analysis, numerical modeling, hydraulics, municipal, water distribution, PRV representation, friction coefficient, Hazen–Williams, flow rate, simulations.
Since the construction of the Bennett Dam on the Peace River in British Columbia, the temperature... more Since the construction of the Bennett Dam on the Peace River in British Columbia, the temperature of flow releases from G.M. Shrum Generation Station, located at the dam, has been 0.5 °C or higher during the winter months. As a result, the progression of ice cover below the dam is inhibited and a long reach of ice-free river persists throughout the winter. During February, 1979 below normal air temperatures persisted in the area and the cover progressed to a point 103 km downstream of the dam, or 19 km upstream of the Water Survey of Canada (WSC) stream gauge at Taylor. This was only the second occurrence of ice cover at the town of Taylor since 1972, when an increase in generating capacity at the G.M. Shrum Station raised maximum powerhouse releases to 1580 m3/s.A series of ice jams at the leading edge of the ice cover formed as the cover advanced, producing water levels within Taylor that approached the maximum historic summer flood levels. The ice movement, including ice cover ad...
There has been considerable research on modelling various aspects of drought such as identificati... more There has been considerable research on modelling various aspects of drought such as identification and prediction of its duration and severity. The term severity has various connotations in drought literature such as in hydrological drought, where it is defined as the cumulative shortage or the deficit sum with reference to a pre-specified truncation level. In meteorological drought, the severity has rather been defined in the form of indices such as the Palmer drought severity index. There exist a variety of techniques and methods to analyse the duration and severity of meteorological and hydrological droughts through probability characterization of low flows, time series methods, synthetic data generation, theory of runs, multiple regression, group theory, pattern recognition and neural network methods. Agricultural droughts are analysed based on soil moisture modelling concepts with crop yield considerations and using multiple linear regression techniques. The prediction aspects of drought duration are developed better than the drought severity aspects. These latter need to be improved because information on drought severity is of paramount practical importance and forms an essential part of the design process of storage facilities for abatement of droughts. A major challenge of drought research is to develop suitable methods and techniques for forecasting the onset and termination points of droughts. An equally challenging task is the dissemination of drought research results for practical usage and wider applications.
A trial is made to explore the applicability of chaos analysis outside the commonly reported anal... more A trial is made to explore the applicability of chaos analysis outside the commonly reported analysis of a single chaotic time series. Two cross-correlated streamflows, the Little River and the Reed Creek, Virginia, USA, are analysed with regard to the chaotic behaviour. Segments of missing data are assumed in one of the time series and estimated using the other complete time series. Linear regression and artificial neural network models are employed. Two experiments are conducted in the analysis: (a) fitting one global model and (b) fitting multiple local models. Each local model is in the direct vicinity of the missing data. A nonlinear noise reduction method is used to reduce the noise in both time series and the two experiments are repeated. It is found that using multiple local models to estimate the missing data is superior to fitting one global model with regard to the mean squared error and the mean relative error of the estimated values. This result is attributed to the cha...
There has been considerable research on modelling various aspects of drought such as identificati... more There has been considerable research on modelling various aspects of drought such as identification and prediction of its duration and severity. The term severity has various connotations in drought literature such as in hydrological drought, where it is defined as the cumulative shortage or the deficit sum with reference to a pre-specified truncation level. In meteorological drought, the severity has rather been defined in the form of indices such as the Palmer drought severity index. There exist a variety of techniques and methods to analyse the duration and severity of meteorological and hydrological droughts through probability characterization of low flows, time series methods, synthetic data generation, theory of runs, multiple regression, group theory, pattern recognition and neural network methods. Agricultural droughts are analysed based on soil moisture modelling concepts with crop yield considerations and using multiple linear regression techniques. The prediction aspects...
Stochastic weather modeling of daily precipitation amounts is frequently subject to a number of c... more Stochastic weather modeling of daily precipitation amounts is frequently subject to a number of challenges, e.g., the difficulty in modeling the unique statistical characteristics of observations. The difficulty could further be complicated when the varied spatial-dependency of observations at multiple sites and the uncertainty induced by the existence of missing observations are considered. A multivariate truncated Normal distribution model is proposed to transform the skewed distribution of precipitation amounts at multiple sites into a multivariate Normal distribution model. The missing observations are then estimated through the conditional simulation using the parameters obtained from the multivariate Normal distribution model. Historical daily precipitation records from 10 Canadian meteorological stations in the Winnipeg region were utilized to evaluate the efficacy of the model. The evaluation results show that the model can reasonably preserve the statistical characteristics...
An assessment of the existing theoretical expressions of flow into perforated draintubes has been... more An assessment of the existing theoretical expressions of flow into perforated draintubes has been made in regard to their applicability in the estimation of flow rate into perforated drains under field conditions. A method based on the experimental results is proposed for extending the application of existing expressions to curved watertable conditions.
In large water distribution networks, pressure reducing valves (PRVs) are common water appurtenan... more In large water distribution networks, pressure reducing valves (PRVs) are common water appurtenances. However, there are difficulties in representing them when using the Hazen-Williams friction factor in network-analysis models. This paper focuses on such difficulties and suggests a procedure for resolving them through the use of a modified Hazen-Williams friction factor. The effectiveness of the proposed modification in representing PRVs in the WATER model is demonstrated.
To address the challenge of obtaining reliable streamflow data for water resource management, thi... more To address the challenge of obtaining reliable streamflow data for water resource management, this paper develops an encoding scheme to transform a streamflow time series into an 8-bit grayscale image where it is feasible to develop a correlation between neighbouring pixels to reveal patterns that are not easily discernable in traditional time series analysis. To extract relevant information from an encoded streamflow image, a novel textural feature extraction approach has been developed for synthesizing streamflow data. The developed textural feature extraction model can capture the simultaneous correlation in two dimensions of an encoded streamflow image, which is then transformed into the frequency domain using a discrete Fourier transform. The use of the power spectrum of the Fourier coefficients facilitates the synthesis of encoded streamflow images. The effectiveness of the model is evaluated using three case studies across Canada by comparing the properties of synthesized str...
Daily streamflows; Mutual information; Embedding dimension; Hurst coefficient Summary The existen... more Daily streamflows; Mutual information; Embedding dimension; Hurst coefficient Summary The existence of outliers in data sets affects the decision-making process related to design, operation, and management of water resources. Insufficient informa- tion on outliers limits our understanding and predictive ability of such extreme hydrologic phenomena. Hydrologic systems are complex and dynamic in nature where current state and future evolutions depend
Among the various methods for estimating reservoir volumes, the Gould probability matrix (GPM) me... more Among the various methods for estimating reservoir volumes, the Gould probability matrix (GPM) method has been touted as a powerful method for estimating reservoir volumes. The other methods in vogue are the Behavior analysis (BA) with the latest induction of the Drought magnitude (DM) method. A comparison of the above methods in terms of ease, efficiency, and relative merits from each other is currently lacking in the literature. This paper compares the above three methods with a detailed analysis of the GPM method using the monthly flows from 16 Canadian rivers at the draft ratios of 75 and 50% with the probability of failure of 2.5, 5 and 10%. The results reported in this paper indicate that fifteen zones are sufficient in the GPM method to yield the reservoir capacity for the Canadian rivers while requiring no standardization of the data, similar to the BA method. In the DM method, standardized monthly flow sequences in combination with a scaling parameter Φ yielded effective dr...
... 4. Significance of neural networks in monthly streamflow data. Monthly streamflows are often ... more ... 4. Significance of neural networks in monthly streamflow data. Monthly streamflows are often short and exhibit a nonlinear multi-variable nature and this can make it ... ANN models have been applied to solve problems concerning missing data and data forecasting in hydrology ...
Uniqueness of the problem surrounding non-detects has been a concern alike to researchers and sta... more Uniqueness of the problem surrounding non-detects has been a concern alike to researchers and statisticians dealing with summary statistics while analyzing censored data. To incorporate non-detects in the estimation process, a simple substitution by the MDL (method detection limit) and the maximum likelihood estimation method are routinely implemented as standard methods by US-EPA laboratories. In situations where numerical standards are set at or near the MDL by regulatory agencies, it is prudent and important to closely investigate both the variability in test measurements and the estimation bias, because an inference based on biased estimates could entail significant liabilities. Variability is understood to be not only inevitable but also an inherent and integral part of any chemical analysis or test. In situations where regulatory agencies fail to account for the inherently present variability of test measurements, there is a need for regulated facilities to seek remedial action merely as a consequence of inadequate statistical procedure. This paper utilizes a mathematical approach to derive the bias functions and resulting bias curves are developed to investigate the censored samples from a variety of probability distributions such as normal, log-normal, gamma, and Gumbel distributions. Finally, the bias functions and bias curves are also compared to the results obtained by using Monte Carlo simulations.
Page 1. This article was downloaded by: [66.249.68.69] On: 08 July 2011, At: 00:43 Publisher: Tay... more Page 1. This article was downloaded by: [66.249.68.69] On: 08 July 2011, At: 00:43 Publisher: Taylor & Francis Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK ...
Preferential accumulation of minerals with high densities forming placer deposits in longitudinal... more Preferential accumulation of minerals with high densities forming placer deposits in longitudinal bars of braided rivers relies on the segregation of this denser material from the quartz and feldspar sands dominating sediment in transport. Flume experimentation conducted on mixtures of quartz, pyroxene, magnetite, and lead sand transported over rough cobble beds demonstrated that the sand distribution was more uniform above the bed than theory predicted. The deviation from theory was inversely proportional to the density of the mineral. Fall velocity was not a good predictor of the amount of a mineral species carried in suspension, as coarsegrained quartz dominated the suspension population in the flume runs where lead was a major constituent in the traction population, even though the quartz had a greater fall velocity. Applying these results to placer deposits indicates that during flood events, even the smaller dense minerals and especially the super-dense minerals will be transported with the gravel and cobble load, whereas the quartz and feldspar will be spatially segregated during transport and temporally and spatially segregated during deposition. This mechanism of placer formation is capable of creating the types of deposits present in orebodies and showings such as the uraniferous paleoplacers at Elliot Lake, Canada, and the gold-bearing longitudinal bars in the Witwatersrand.
Computer models are no longer viewed as exotic luxuries, rather they are being increasingly accep... more Computer models are no longer viewed as exotic luxuries, rather they are being increasingly accepted as necessities for effective planning and operation of water distribution systems. In large networks, pressure-reducing valves (PRVs) are common water appurtenances. However, through the use of the Hazen–Williams friction factor, there are difficulties in representing PRVs in network-analysis models. This paper focuses on these difficulties and suggests a procedure for resolving them through the use of modified Hazen–Williams friction factor. The effectiveness of the proposed modification in representing PRVs in the WATER model is demonstrated. Key words: network analysis, numerical modeling, hydraulics, municipal, water distribution, PRV representation, friction coefficient, Hazen–Williams, flow rate, simulations.
Since the construction of the Bennett Dam on the Peace River in British Columbia, the temperature... more Since the construction of the Bennett Dam on the Peace River in British Columbia, the temperature of flow releases from G.M. Shrum Generation Station, located at the dam, has been 0.5 °C or higher during the winter months. As a result, the progression of ice cover below the dam is inhibited and a long reach of ice-free river persists throughout the winter. During February, 1979 below normal air temperatures persisted in the area and the cover progressed to a point 103 km downstream of the dam, or 19 km upstream of the Water Survey of Canada (WSC) stream gauge at Taylor. This was only the second occurrence of ice cover at the town of Taylor since 1972, when an increase in generating capacity at the G.M. Shrum Station raised maximum powerhouse releases to 1580 m3/s.A series of ice jams at the leading edge of the ice cover formed as the cover advanced, producing water levels within Taylor that approached the maximum historic summer flood levels. The ice movement, including ice cover ad...
There has been considerable research on modelling various aspects of drought such as identificati... more There has been considerable research on modelling various aspects of drought such as identification and prediction of its duration and severity. The term severity has various connotations in drought literature such as in hydrological drought, where it is defined as the cumulative shortage or the deficit sum with reference to a pre-specified truncation level. In meteorological drought, the severity has rather been defined in the form of indices such as the Palmer drought severity index. There exist a variety of techniques and methods to analyse the duration and severity of meteorological and hydrological droughts through probability characterization of low flows, time series methods, synthetic data generation, theory of runs, multiple regression, group theory, pattern recognition and neural network methods. Agricultural droughts are analysed based on soil moisture modelling concepts with crop yield considerations and using multiple linear regression techniques. The prediction aspects of drought duration are developed better than the drought severity aspects. These latter need to be improved because information on drought severity is of paramount practical importance and forms an essential part of the design process of storage facilities for abatement of droughts. A major challenge of drought research is to develop suitable methods and techniques for forecasting the onset and termination points of droughts. An equally challenging task is the dissemination of drought research results for practical usage and wider applications.
A trial is made to explore the applicability of chaos analysis outside the commonly reported anal... more A trial is made to explore the applicability of chaos analysis outside the commonly reported analysis of a single chaotic time series. Two cross-correlated streamflows, the Little River and the Reed Creek, Virginia, USA, are analysed with regard to the chaotic behaviour. Segments of missing data are assumed in one of the time series and estimated using the other complete time series. Linear regression and artificial neural network models are employed. Two experiments are conducted in the analysis: (a) fitting one global model and (b) fitting multiple local models. Each local model is in the direct vicinity of the missing data. A nonlinear noise reduction method is used to reduce the noise in both time series and the two experiments are repeated. It is found that using multiple local models to estimate the missing data is superior to fitting one global model with regard to the mean squared error and the mean relative error of the estimated values. This result is attributed to the cha...
There has been considerable research on modelling various aspects of drought such as identificati... more There has been considerable research on modelling various aspects of drought such as identification and prediction of its duration and severity. The term severity has various connotations in drought literature such as in hydrological drought, where it is defined as the cumulative shortage or the deficit sum with reference to a pre-specified truncation level. In meteorological drought, the severity has rather been defined in the form of indices such as the Palmer drought severity index. There exist a variety of techniques and methods to analyse the duration and severity of meteorological and hydrological droughts through probability characterization of low flows, time series methods, synthetic data generation, theory of runs, multiple regression, group theory, pattern recognition and neural network methods. Agricultural droughts are analysed based on soil moisture modelling concepts with crop yield considerations and using multiple linear regression techniques. The prediction aspects...
Stochastic weather modeling of daily precipitation amounts is frequently subject to a number of c... more Stochastic weather modeling of daily precipitation amounts is frequently subject to a number of challenges, e.g., the difficulty in modeling the unique statistical characteristics of observations. The difficulty could further be complicated when the varied spatial-dependency of observations at multiple sites and the uncertainty induced by the existence of missing observations are considered. A multivariate truncated Normal distribution model is proposed to transform the skewed distribution of precipitation amounts at multiple sites into a multivariate Normal distribution model. The missing observations are then estimated through the conditional simulation using the parameters obtained from the multivariate Normal distribution model. Historical daily precipitation records from 10 Canadian meteorological stations in the Winnipeg region were utilized to evaluate the efficacy of the model. The evaluation results show that the model can reasonably preserve the statistical characteristics...
An assessment of the existing theoretical expressions of flow into perforated draintubes has been... more An assessment of the existing theoretical expressions of flow into perforated draintubes has been made in regard to their applicability in the estimation of flow rate into perforated drains under field conditions. A method based on the experimental results is proposed for extending the application of existing expressions to curved watertable conditions.
In large water distribution networks, pressure reducing valves (PRVs) are common water appurtenan... more In large water distribution networks, pressure reducing valves (PRVs) are common water appurtenances. However, there are difficulties in representing them when using the Hazen-Williams friction factor in network-analysis models. This paper focuses on such difficulties and suggests a procedure for resolving them through the use of a modified Hazen-Williams friction factor. The effectiveness of the proposed modification in representing PRVs in the WATER model is demonstrated.
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