Uluslararası Hakemli Dergilerde Yayınlanmış Makaleler

Discussion of "Development of Exceedance Probability Streamflow Forecast" by Thomas C. Piechota, Francis H. S. Chiew, John A. Dracup, and Thomas A. McMahon, J. Hydrol. Engrg., ASCE, 7(3), 265-267

Şen, Z. and Altunkaynak, A., 2002

The authors have described a method of streamflow prediction through the use of the exceedance probability concept. The basis of the concept is identical with the flow duration curve surface hydrology (Cigizoglu and Bayazit 2000). In both the development and the application of their methodology there are some vague considerations and points that need further clarification. It is true that the reliable estimation of streamflows is necessary in any water resources development and management. However, from meteorological and atmospheric views, this paper should try and search for such a prediction for the precipitation records. For the major hydrological variable streamflow is shaped by topographic, morphologic, vegetative, and surface geological characteristics of a region based on the precipitation event occurrences.

Triple diagram model of level fluctuations in Lake Van, Turkey, Hydrology and Earth Sys. Scien., 7(2), 235-244

Altunkaynak, A, Özger, M. and Şen, Z., 2003.

This paper presents a triple diagram method (TDM) based on the Kriging technique for predicting future lake levels from two antecedent measurements, which are considered as independent variables. The experimental semivariograms (SV) for three lags are obtained, and the most suitable theoretical SV for the three cases is the Gaussian type. Based on these theoretical SVs, the contour lines of the dependent variable are constructed by Kriging. The resulting maps are referred to as the TDM model for lake level fluctuation. It is expected that this model will be used more extensively than the Markov or ARIMA (AutoRegressive Integrated Moving Average) models commonly available for stochastic modelling and predictions. The TDM does not have restrictive assumptions such as the stationarity and ergodicity which are preliminary requirements for the stochastic modelling. The TDM is applied to monthly level fluctuations of Lake Van in eastern Turkey. In the prediction procedure lags, one, two and three are considered. Interpretations from these three basic diagrams help to identify properties of lake level fluctuations. It is observed that the TDM preserves the statistical properties. These diagrams also help to make predictions with less than 10 % relative error.

Autorun persistence of hydrologic design, J. of Hydrol. Engrg., ASCE, 8(6), 329-338

Şen, Z., Altunkaynak, A. and Özger, M., 2003

Persistence is the most important property in any hydrologic design concerning the storage capacity of reservoirs, average return periods, failure risks, and drought properties. Its consideration in analytical derivations of design criteria presents difficulties, especially in autocorrelated hydrologic processes, and for this reason, most often the analytical expressions are obtained on the basis of non-persistent (independent) cases. Although the conventional autocorrelation coefficients and function are used in many hydrological design problems, the very definition of the autocorrelation function requires that the underlying hydrologic process generating mechanism abide with normal (Gaussian) probability distribution function in addition to other restrictive assumptions. Since almost all of the analytical stochastic approaches are based on the normality assumption, it is necessary to transform non-Gaussian distributions to the normal distribution to use analytical expressions. During the transformation process, the very genuine persistence property of the basic hydrologic variables is not preserved, even when the statistical parameters such as the average, standard deviation, skewness coefficient, kurtosis, etc., are maintained in the transformed data. This shortcoming in the autocorrelation function is by-passed by the introduction and use of an autorun function, which is probability distribution free and a robust parameter. Its basis is the conditional probability statement which does not require any assumptions in practical applications. Various practical and simple hydrological design quantities are developed on the basis of the autorun coefficients without considering the conventional autocorrelation structure. The application of methodology is presented for John’s river in Florida.

DOI: 10.1061/(ASCE)1084-0699(2003)8:6(329)

CE Database subject headings: Hydrology; Frequency; Risk; Probability; Water storage; Design.

Increasing water supply by mixing of fresh and saline ground waters. J. Amer. Water Res. Assoc., 39(5), 1209-1215

Şen, Z., Saud, A.A., Altunkaynak, A. and Özger, M., 2003

The quality of ground water in any aquifer takes its final form due to natural mixture of waters, which may originate from different sources. Water quality varies from one aquifer to another and even within the same aquifer itself. Different ground water quality is obtained from wells and is mixed in a common reservoir prior to any consumption. This artificial mixing enables an increase in available ground water of a desired quality for agricultural or residential purposes. The question remains as to what proportions of water from different wells should be mixed together to achieve a desired water quality for this artificial mixture. Two sets of laboratory experiments were carried out, namely, the addition of saline water to a fixed volume of fresh water. After each addition, the mixture volume and the electric conductivity value of the artificially mixed water were recorded. The experiments were carried out under the same laboratory temperature of 20°C. A standard curve was developed first experimentally and then confirmed theoretically. This curve is useful in determining either the volume or discharge ratio from two wells to achieve a predetermined electrical conductivity value of the artificial mixture. The application of the curve is given for two wells within the Quaternary deposits in the western part of the Kingdom of Saudi Arabia

Fuzzy awakening in rainfall and runoff modeling. Nordic Hydrology, 35(1), 31-43

Şen, Z. and Altunkaynak, A., 2004

Rainfall-runoff relationships are widely used in many engineering hydrologic designs in urban and rural areas. Such relationships are obtained through the application of regression analysis in many studies. Unfortunately, in the classical regression approach to determine rainfall-runoff relationships, internal uncertainties are not taken explicitly into consideration. In this paper, an alternative to the classical regression approach is proposed through fuzzy system modeling. It is concluded that the fuzzy systems approach yields comparatively less relative error than a regression approach and, therefore, it is recommended for use in future. The application is presented for rainfall-runoff records at two sites near Istanbul, Turkey.

Statistical investigation expected wave energy and its reliability, Energy Conv. & Management, 45(13-14), 2173-2185

Özger, M., Altunkaynak, A. and Şen, Z., 2004

The statistical behavior of wave energy at a single site is derived by considering simultaneous variations in the period and wave height. In this paper, the general wave power formulation is derived by using the theory of perturbation. This method leads to a general formulation of the wave power expectation and other statistical parameter expressions, such as standard deviation and coefficient of variation. The statistical parameters, namely the mean value and variance of wave energy, are found in terms of the simple statistical parameters of period, significant wave height and zero up-crossing period. The elegance of these parameters is that they are distribution free. These parameters provide a means for defining the wave energy distribution function by employing the Chebyschev’s inequality. Subsequently, an approximate probability distribution function of the wave energy is also derived for assessment of risk and reliability associated with wave energy. Necessary simple charts are given for risk and reliability assessments. Two procedures are presented for such assessments in wave energy calculations and the applications of these procedures are provided for wave energy potential assessment in the regions of the Pacific Ocean off the west coast of U.S. ©2003 Elsevier Ltd. All rights reserved.

Stochastic wave energy calculation formulation, Renewable Energy, 29(10), 1747-1756

Özger, M., Altunkaynak, A. and Şen, Z., 2004

The wave energy potential is directly proportional to the wave period and second power of wave height averaged over a suitable time period. The wave height and period have temporal and spatial stochastic variations. It is the main purpose of this paper to derive the most general wave energy formulation by considering simultaneously the temporal variations both in the wave height and period. The correction factor is derived explicitly in terms of cross-correlation and the coefficients of variation. The application of the methodology is performed for wave measurement stations located in the Pacific Ocean off the west coast of the US

Temporal significant wave height estimation from wind speed by perceptron Kalman filtering, Ocean Engrg., 31(10), 1245-1257

Altunkaynak, A. and Özger, M. 2004

Significant wave height estimates are necessary for many applications in coastal and offshore engineering and therefore various estimation models are proposed in the literature for this purpose. Unfortunately, most of these models provide simultaneous wave height estimations from wind speed measurements. However, in practical studies, the prediction of significant wave height is necessary from previous time interval measurements. This paper presents a dynamic significant wave height prediction procedure based on the perceptron Kalman filtering concepts. Past measurements of significant wave height and wind speed variables are used for training the adaptive model and it is then employed to predict the significant wave height amounts for future time intervals from the wind speed measurements only. The verification of the proposed model is achieved through the dynamic significant wave height and wind speed time series plots, observed versus predicted values scatter diagram and the classical linear significant wave height models. The application of the proposed model is presented for a station in USA

ENSO Templates and streamflow prediction, J. of Hydrol. Engrg., ASCE, 9 (5) : 368-374

Şen, Z., Altunkaynak, A. and Özger, M., 2004

The El Nino Southern Oscillation (ENSO) template concept is presented for seasonal streamflow prediction methodology by considering the Southern Oscillation Index (SOI) and Sea Surface Temperature (SST) variables. The methodology provides linguistic and quantitative inference capabilities. The prediction model uses the geostatistical (Kriging) technique. Each ENSO template has nine categories including one with high SST and low SOI values that represents the El Nino event. Similarly, the category with low SST and high SOI values depicts the La Nina event. The application of the methodology is presented for the seasonal streamflow records in the southeastern part of the Australian continent along the Pacific Ocean. April–September streamflow is predicted by using five different lead times including 3-month ENSO indicator averages. The seasonal streamflow predictions at different lag times are obtained given the values of SST and SOI. The overall relative prediction error is rather small at about 13%. The bigger the lag the bigger is the prediction error. However, the relative error between averages of observation and prediction values is less than 5%. Similar ENSO templates can be used for streamflow prediction in other parts of the world.
DOI: 10.1061/(ASCE)1084-0699(2004)9:5(368)

CE Database subject headings: Steamflow; Predictions; Seasonal variations; Models.

Sediment concentration and its prediction by Perceptron Kalman Filtering procedure, J. Hydraul. Engrg., ASCE, 130 (8) : 816-826

Şen, Z., Altunkaynak, A. and Özger, M., 2004

Abstract:
Predictions of the discharge and the associated sediment concentration are very useful ingredients in any water resources reservoir design, planning, maintenance, and operation. Although there are many empirical relationships between the discharge and sediment concentration amounts, they need estimation of model parameters. Generally, parameter estimations are achieved through the regression method (RM), which has several restrictive assumptions. Such models are locally valid and their structures and parameter values are questionable from region to others. This paper proposes a new approach for sediment concentration prediction provided that there are measurements of discharge and sediment concentration. The basis of the methodology is a dynamic transitional model between successive time instances based on two variables, namely, discharge and sediment concentration measurements. The transition matrix elements are estimated from the measurements through a special form of the artificial neural networks as perceptrons. The sediment concentration predictions from discharge measurements are achieved through a perceptron Kalman filtering (PKF) technique. In the meantime, this technique also provides temporal predictions. A certain portion of the measurement sequence is employed for the model parameter estimations through training and the remaining part is used for the model verification. Detailed comparisons between RM and PKF approaches are presented and, finally, it is shown that the latter model works dynamically by simulating the observation scatter diagram in the best possible manner with smaller prediction errors. The application of the methodology is performed for the discharge and sediment concentration measurements obtained from the Mississippi River basin at St. Louis, Missouri. It is found that the PKF methodology has smaller average relative, root-mean-square, and absolute errors than RM. Furthermore, graphical representation, such as the scatter and frequency diagrams, indicated that the PKF approach has superiority over the RM.
DOI: 10.1061/(ASCE)0733-9429(2004)130:8(816)

CE Database subject headings: Discharge measurement; Concentration; Kalman filter; Predictions; Sedimentation.

Water Consumption Prediction of Istanbul City by Using Fuzzy Logic Approach, Water Resour. Mangmt., 19, 641-654

Altunkaynak, A., Özger, M. and akmakı, M. 2005

Abstract.
This paper presents a Takagi Sugeno (TS) fuzzy method for predicting future monthly water consumption values from three antecedent water consumption amounts, which are considered as independent variables. Mean square error (MSE) values for different model configurations are obtained, and the most effective model is selected. It is expected that this model will be more extensively used than Markov or ARIMA (AutoRegressive Integrated Moving Average) models commonly available for stochastic modeling and predictions. The TS fuzzy model does not have restrictive assumptions such as the stationarity and ergodicity which are primary requirements for the stochastic modeling. The TS fuzzy model is applied to monthly water consumption fluctuations of Istanbul city in Turkey. In the prediction procedure only lag one is considered. It is observed that the TS fuzzy model preserves the statistical properties. This model also helps to make predictions with less than 10% relative error.

Key words: fluctuation, fuzzy logic, Markov, prediction, water consumption

Variable discharge type curve solutions for confined aquifers. J. Amer. Water Res. Assoc., 40(4), 1189-1196

Şen, Z. and Altunkaynak, A. 2004

Spatial assessment of variables in a considered region saves its significance for engineering applications. Branches in ocean engineering need the results of this assessment like radius of influence of stations that records the wave measurements and various meteorological variables values. Classical approaches like Kriging do not provide radius of influence for the concerned station. On the other hand, prediction of these measurements from other surrounding stations in the region is a basic requirement. In this paper, it is aimed to predict significant wave height records in a specific region by using trigonometric point cumulative semivariogram (TPCSV) concept. The main difference of this approach from the point cumulative semivariogram (PCSV) approach is the determination of influence radius. More accurate results can be obtained by TPCSV. The spatial correlation and weightings are also obtained through the TPCSV where the distance between two sites is known. The proposed method yields the least prediction error compared with other objective methodologies. The implementation of this methodology is presented for a set of offshore locations distributed along the west United States coastline.

Keywords: Area of influence; Estimation; Interpolation; Objective analysis; Radius of influence; Semivariogram; Significant wave height

Significant wave height prediction by using a spatial model, Ocean Engrg.,32 (8-9), 924-936

Altunkaynak, A. 2005

Spatial assessment of variables in a considered region saves its significance for engineering applications. Branches in ocean engineering need the results of this assessment like radius of influence of stations that records the wave measurements and various meteorological variables values. Classical approaches like Kriging do not provide radius of influence for the concerned station. On the other hand, prediction of these measurements from other surrounding stations in the region is a basic requirement. In this paper, it is aimed to predict significant wave height records in a specific region by using trigonometric point cumulative semivariogram (TPCSV) concept. The main difference of this approach from the point cumulative semivariogram (PCSV) approach is the determination of influence radius. More accurate results can be obtained by TPCSV. The spatial correlation and weightings are also obtained through the TPCSV where the distance between two sites is known. The proposed method yields the least prediction error compared with other objective methodologies. The implementation of this methodology is presented for a set of offshore locations distributed along the west United States coastline.

Keywords: Area of influence; Estimation; Interpolation; Objective analysis; Radius of influence; Semivariogram; Significant wave height

Regional Streamflow Estimation By Standard Regional Dependence Function Approach, J. Hydraul. Engrg., ASCE, 131(11), 1001-1006

Altunkaynak, A., Özger, M. and Şen, Z. 2005

Abstract:
The main purpose of this paper is to propose a standard regional dependence function (SRDF) based on concepts of semivariogram and especially point cumulative semivariogram for regional streamflow estimation. The SRDFs are obtained from available spatial data and show regional dependence, which decreases with distance from a given site. These functions present quantitatively the regional dependence of the streamflow phenomenon recorded at irregular sites over a drainage basin and provide a unique opportunity for the establishment of regional objective estimation method based on weighed averages. The weightings are obtained by means of the SRDF given the distance between any two sites. The implementation of the proposed methodology is presented for some streamflow records from the Lower and Upper Mississippi River watershed in the United States. For the application, the experimental SRDF forms are first obtained from the available data, and these are then employed directly in the regional estimation procedure. The study indicated that the use of all the stations in a region for the estimation at any particular station is rather naïve because far away stations (more than 1,000 km away) are taken into consideration. The final conclusion is that discharge at any particular station is better described as a function of discharge at several (3–5) closest stations. The reliability of the method is measured through the cross validation procedure, and it is observed that the procedure yields streamflow predictions with less than 10% relative error.

CE Database subject headings: Streamflow; Forecasting; Regional analysis; Mississippi River.

Spatial Significant Wave Height Variation Assessment and its Estimation, J. Wtrwy. Port and Ocean Engrg., ASCE, 131(6), 277-282

Altunkaynak, A., and Özger, M. 2005

Significant wave height is a very important variable used in ocean engineering studies. Spatial variation of the significant wave height is very important for wave energy abstraction studies which is highly dependent on the wave climate. Significant wave height and period are two of the most important wave features that directly affect the energy production. In nature these two variables exhibit temporal randomness and spatial changes. These variations cause heterogeneous regional dispersion of wave energy. In order to assess regional energy distribution, it is necessary to use the concept of regionalized variables through geostatistical methods. The main purpose of this paper is to evaluate the spatial characteristics of significant wave height by the point cumulative semivariogram approach leading to a standard regional dependence function (SRDF) based on concepts of the semivariogram. It is also possible to estimate the unmeasured station value from the closest stations by using SRDF and determine the optimum station intervals. The SRDFs are obtained from available spatial data decreasing with distance for a given set of sites. The wave energy resource in a region of the Pacific Ocean off the west coast of the United States has been evaluated as the application of proposed methodology. It is found that spatial modeling of the region considered can be achieved by using the SRDF function in acceptable error limits.

CE Database subject headings: Ocean waves; Spatial analysis; Wave energy; Weighing devices; Wave height; Wave climatology.

Fuzzy Logic Modeling of the Dissolved Oxygen Fluctuations in Golden Horn, Ecological Modeling, 189 (3-4), 436-446

Altunkaynak, A., Özger, M. and akmakı, M. 2005

Abstract
The modern modeling techniques show a significant progress in recent years. Fuzzy logic approach is one of these methods that can be used for forecasting purposes and identification of complex systems. In this study, it is aimed to model monthly dissolved oxygen (DO) amount variations. Firstly, regression technique is used to remove the trend from the actual dissolved oxygen time series. Detrended time series is then modeled with Takagi–Sugeno Fuzzy logic approach. The monthly historical records of DO as considered in this paper provide a fundamental data exhibiting persistence. It is this dependence that gives opportunity for the serial modeling of the data sequence concerned. These models are the prime and sole means to derive the future likely excedences over the historical values and hence provide a chance for the future planner with decision variables such as the minimum DO amounts and their persistence for some duration. In the scope of this study, DO concentration changes in the two stations located in Golden Horn at the 0.5m (upper layer) depth were modeled. As a result of the study, it is seen that one can forecast the next month’s DO amount from antecedent measurements within an acceptable relative error limits.

Keywords: Concentration dissolved oxygen; Forecast; Fuzzy logic; Golden Horn

A Comparative Fuzzy Logic Approach to Runoff Coefficient and Runoff Estimation, Hydrol. Process., 20 (9): 1993-2009

Şen, Z., and Altunkaynak, 2005

In practice, rainfall–runoff relationships are achieved through a simply defined runoff coefficient concept that is widely used in many engineering hydrological designs in urban and rural areas. The simplicity of the method, with the sole requirement of runoff coefficient assessment, is the main attractiveness, in addition to its successful prediction of average runoff rates for a given rainfall record. Unfortunately, in the classical regression approach of the rainfall–runoff relationship, internal variabilities are not taken into consideration explicitly. The runoff coefficient is considered a constant value, and it is used without distinction of antecedent conditions for the calculation of runoff from the rainfall record. In this paper, various other uncertainty embedded versions of the runoff coefficient, and hence rainfall–runoff formulation, are presented in terms of statistics, probability, perturbation and, finally, fuzzy system modelling. It is concluded that the fuzzy logic approach yields the least relative error among the various alternative runoff calculation methods; therefore, it is recommended for use in future studies. The application of various alternatives is presented for two monthly rainfall-runoff records around Istanbul, Turkey.

KEY WORDS fuzzy logic; perturbation; prediction; rainfall-runoff; hydrological modelling

Space-Time Interpolation by Combining Air Pollution and Meteorological Variables. Pure Appl. Geophy., 163 (7): 1435-1451

Şen, Z., Altunkaynak, A. and Özger, M., 2005

Abstract
In this paper, a technique is proposed in order to study triple time series. It combines the variable of interest, sulfur dioxide (SO2) with two related meteorological variables. Hence, three variables measured at the same time points are jointly analyzed. Instead of using classical multiple time series analysis, it is suggested to consider the measurements of the two meteorological variables as coordinates of a two-dimensional space and the simultaneous observation of the third variable (associated SO2 concentrations) at each pair of coordinates. Subsequently, well-known optimum interpolation is used for predicting the SO2 concentrations on the basis of six meteorological variables. All the variables of the study are measured at the same times (all days in 2000) around the city of Istanbul, Turkey. The triple diagrams, in the form of contour maps, help to answer various questions concerning the SO2 concentration variability with respect to meteorological variables. The same diagrams also provide a basis for the prediction of SO2 concentrations. It is shown that the relative prediction error is less than 10%, which is acceptable for the practical studies.

Key words: Kriging, air pollution, optimum interpolation, prediction.

Fuzzy Logic Model for Equilibrium Scour Downstream of a Dam?s Vertical Gate, J. Hydraul. Engrg., ASCE, 132 (10): 1069-1075

Uyumaz, A., Altunkaynak, A. and Özger, M., 2006

Abstract:
Scour at a downstream vertical gate of a dam is investigated using a fuzzy logic inference system. The application is presented for experimental data sets. A comparison is made between a regression formulation (RM) and a fuzzy logic approach. Some restrictive assumptions for RM are discussed. Here the Takagi–Sugeno (TS) approach is used with a constant function in the consequent part of the fuzzy rules. It is demonstrated that the TS model gives a lower error than the RM. Furthermore, scatter diagrams indicate that the TS approach has superiority over the RM.

CE Database subject headings: Scour; Fuzzy sets; Hydraulic engineering; Regression analysis; Gates; Dams.

Discussion of Estimation of wave spectral shapes using ANN by Naithani R and Deo MC,Advances in Engineering Software, 38(1), 68

Özger, M and Altunkaynak, A. 2007

The authors have presented a methodology based on artificial neural network (ANN) approach to estimate wave energy spectrum. The ANN model results then compared with the classical models such as JONSWAP, Pierson–Moskowitz (PM) and Scott spectrums.

The discussion shall focus on three main points that is not considered in the study. The first one is about the selection of input variables of the ANN model. The authors stated that the objective of the study is to derive wave energy spectrum from the wave parameters such as significant wave height, Hs, zero up-crossing period, Tz, spectral width, e and peakedness, Qp. While deriving the spectra these parameters are assumed to be known. However this assumption is not useful for practical applications. The use of Hs and Tz for design purposes may be practical but e and Qp cannot be easily interpreted by the user to extract a physical meaning.

Forecasting surface water level fluctuations of Lake Van by artificial neural networks, Water Resources Management, 21 (2), 399-408

Altunkaynak, A., 2007

Abstract
Lake Van in eastern Turkey has been subject to water level rise during the last decade and, consequently, the low-lying areas along the shore are inundated, giving problems to local administrators, governmental officials, irrigation activities and to people’s property. Therefore, forecasting water levels of the Lake has started to attract the attention of the researchers in the country. An attempt has been made to use artificial neural networks (ANN) for modeling the temporal change water levels of Lake Van. A back-propagation algorithm is used for training. The study indicated that neural networks can successfully model the complex relationship between the rainfall and consecutive water levels. Three different cases were considered with the network trained for different arrangements of input nodes, such as current and antecedent lake levels, rainfall amounts. All of the three models yields relatively close results to each other. The neural network model is simpler and more reliable than the conventional methods such as autoregressive (AR), moving average (MA), and autoregressive moving average with exogenous input (ARMAX) models. It is shown that the relative errors for these two different models, are below 10% which is acceptable for engineering studies. In this study, dynamic changes of the lake level are evaluated. In contrast to classical methods, ANNs do not require strict assumptions such as linearity, normality, homoscadacity etc.

Keywords Hydrologic budget . Lake level . Neural networks . Prediction

Steady-state groundwater flow model with variable hydraulic conductivity. Hydrol. Scien. Jour., 52(1), 221-229

Altunkaynak, A. 2007

Abstract
Classical aquifer test models assume an isotropic and homogenous medium with Darcian flow as an ideal case. Deviations from type curves indicate the heterogeneity of the aquifer. There are heterogeneities even at small scales. There are also systematic variations which are not considered by type curves. For instance, due to the groundwater movement during the well-development phase, the hydraulic conductivity tends to decrease with radial distance from the well. For practical representation of such a systematic variation, a linear hydraulic conductivity decrease is adopted and the relevant type curve expressions are derived. These expressions are checked against the classical constant hydraulic conductivity solutions in the literature. Derived type curves are employed for the identification of aquifer parameters, namely transmissivity and the radial hydraulic conductivity variation parameters. The type curve expression derived transforms into the classical Thiem expression when the aquifer hydraulic conductivity is considered as constant. It is observed that classical steady-state flow with constant hydraulic conductivity underestimates the transmissivity by 10%.

Key words Darcy law; groundwater; steady-state flow; type curve; variable hydraulic conductivity

 

Fuzzy logic model of lake water level fluctuations in Lake Van, Turkey, Theor. Appl. Climatol., 90 (3-4), 227-233

Altunkaynak, A. and Şen, Z. 2007

Summary
Lake Van is one of the largest terminal lakes in the world. In recent years, significant lake level fluctuations have occurred and can be related to global climatic change. This fluctuation sometimes exhibits abrupt shifts. Floods originating from the lake can cause considerable damage and loss in agriculture and urban areas. Therefore, water level forecasting plays a significant role in planning and design. This study is aimed at predicting future lake levels from past rainfall amounts and water level records. A dynamical change of the lake level is evaluated by the fuzzy approach. The fuzzy inference system has the ability to use fuzzy membership functions that include the uncertainties of the concerned event. This method is applied for Lake Van, in east Turkey. Furthermore, model capabilities are compared with ARMAX model. It is shown that lower absolute errors are obtained with the Takagi-Sugeno fuzzy approach than with the ARMAX model.

Adaptive estimation of wave parametrers by Geno-Kalman filtering, Ocean Engrg., 35 (2008) 1245?1251

Altunkaynak, A. 2008

Prediction of wave parameters is very important for planning, designing and operation of ocean structures. Accurate estimation of these parameters provides engineers to construct more economical and reliable ocean structures such as harbors, breakwaters, oil production platforms and ocean wave energy converters. For this reason, optimum operation of these plants has become a must. Various methods have been introduced to determine the relation among wind speed previous and current wave parameters. Method proposed in this paper consists of genetic algorithms and Kalman filters which is called as Geno-Kalman filtering. It is based on adaptive calculation to reach the solution. Also a comparison has been made between perceptron Kalman filtering and Geno-Kalman filtering techniques. The application of Geno-Kalman filtering was performed for station 46002 which located in the Coos Bay at Oregon, USA. It is observed that the Geno-Kalman filtering methodology has smaller absolute, mean-square and relative errors than perceptron Kalman filtering. Also coefficient of efficiency value which was used to evaluate results between observed and estimated is higher at Geno-Kalman filtering than perceptron Kalman filtering.

Keywords: Adaptive modeling, Genetic algorithms, Kalman filtering prediction, Wave parameters

Estimation of streamflow by slope Regional Dependency Function, Hydrology and Earth System Sciences., 12, 1121?1127, 2008

Altunkaynak, A. 2008

Kriging is one of the most developed methodologies in the regional variable modeling. However, one of its drawbacks is that the influence radius can not be determined by this method. In which distance and in what ratio that pivot station is influenced from adjacent sites is rather often encountered problem in practical applications. Regional weighting functions obtained from available data consist of several broken lines. Each line has different slopes which represent the similarity and the contribution of adjacent stations as a weighting coefficient. The approach in this study is called as Slope Regional Dependency Function (SRDF). The main idea of this approach is to express the variability in value differences and distances together. Originally proposed SRDF and Trigonometric Point Cumulative Semi-Variogram (TPCSV) methods are used to predict streamflow. TPCSV and Point Cumulative Semi-Variogram (PCSV) approaches are also compared with each other. Prediction performance of all the three methods revealed a relative error less than 10% which is acceptable for most engineering applications. It is shown that SRDF outperforms PCSV and TPCSV with very high differences. It can be used for missing data completion, determination of measurement sites location, calculation of influence radius, and determination of regional variable potential. The proposed method is applied for the 38 stream flow measurement sites located in the Mississippi River basin.

Contour diagram fuzzy model for maximum surface ozone prediction 36 (2009) 6389?6402

Şen,Z., Altunkaynak,A.* and Alp, K.,2009

Abstract


A contour diagram approach is presented for the identification of surface ozone concentration feature based on a set of rules by considering the meteorological variables such as the solar radiation, wind speed, temperature, humidity and rainfall. A fuzzy rule system approach is used because of the imprecise, insufficient, ambiguous and uncertain data available. The contour diagrams help to identify qualitative ozone concentration variability rules which are more general than conventional statistical or time series analysis. In the methodology, ozone concentration contours are based on a fixed variable as ozone precursor, namely, NOx and as the third variable one of the meteorological factors. Such contour diagrams for ozone concentration variation are prepared for six months. It is possible to identify the maximum ozone concentration episodes from these diagrams and then to set up the valid rules in the form of IFTHEN logical statements. These rules are obtained from available daily ozone, NOx and meteorological data as a first approximate reasoning step. In this manner, without mathematical formulations, expert maximum ozone concentration systems are identified. The application of the contour diagram approach is performed for daily ozone concentration measurements on European side of Istanbul city. It is concluded that through approximate reasoning with fuzzy rules, the maximum ozone concentration episodes can be identified and predicted without any mathematical expression.

Key words: Contour diagrams, Fuzzy rules, fuzzy sets, Meteorology, non-parametric approach, ozone concentrations, Vagueness

Sediment load prediction by genetic algorithms,Advances in Engineering Software,40 (2009) 928?934

Altunkaynak,A.,2009

  Abstract

 Accurate sediment load prediction is very important in planning, designing, operating and maintenance of water resources structures. Various models have been developed so far to identify the relation between discharge and sediment load. Most of the models based on regression method (RM) have some restrictive assumptions. This method is able to provide only one solution point for estimation of sediment amount. On the other hand, genetic algorithms (GAs) can produce more than one solution points providing optimal relation between discharge and sediment loads. Sediment load can be successfully predicted from discharge measurements by using GAs. Graphical and numerical data are presented to compare GAs with RM. GA methodology is applied to discharge and sediment load data obtained from Mississippi river at Missouri, St. Louis. It is found that GAs outperform RM in terms of mean relative error (MRE). 

Keywords: Discharg, Genetic algorithms, Prediction, Sediment load 

A predictive model for reach morphology classification in mountain streams using multilayer perceptron methods, WATER RESOURCES RESEARCH , 45, W12501.

Altunkaynak, A. and Strom, K.B. 2009

Classification of reach-scale morphology is useful as a shorthand descriptor of the geomorphic processes andaquatic habitat settings at particular river sections due to thetie between reach-scale form and fluvial and geologic processes. The value of such classifications motivates the development of practical, predictive classification models that operate on measured or predicted reach-scale hydraulic
and sediment conditions. Such models are useful for clas-sifying large sections of channel networks and identifying river sections that are particularly susceptible to changes in flow or sediment conditions which could result from climatic or anthropogenic disturbances [Wohl and Merritt,2005; Flores et al., 2006]. The focus of this paper is on the development of a classification models for mountain stream
reach morphology based on simple input variables that are linked to the underlying processes xpressed in the local morphology types using multilayer perceptron networks.

 

Streamflow estimation using optimal regional dependency function, Hydrological Processes, 23( 25), 3525-3533.

Altunkaynak, A. 2009

The determination of spatial dependency of regionalized variable (ReV) is important in engineering studies. Regional
dependency function that leads to calculation of weighting coef?cients is required in order to make regional or point-wise
estimations. After obtaining this dependency function, it is possible to complete missing records in the time series and locate
new measurement station. Also determination of regional dependency function is also useful to understand the regional variation
of ReV. Point Cumulative Semi-Variogram (PCSV) is another methodology to understand the regional dependency of ReV
related to the magnitude and the location. However, this methodology is not useful to determine the weighting coef?cient,
which is required to make regional and point-wise estimations. However, in Point Semi-Variogram (PSV) proposed here,
weighting coef?cient depends on both magnitude and location. Although the regional dependency function has a ?uctuating
structure in PSV approach, this function gradually increases with distance in PCSV. The study area is selected in Mississippi
river basin with 38 stream?ow stations used for PCSV application before. It is aimed to compare two different geostatistical
models for the same data set. PSV method has an ability to determine the value of variable along with optimum number of
neighbour stations and in?uence radius. PSV and slope PSV approaches are compared with the PCSV. It was shown that slope
slope point semi-variogram (SPSV) approaches had relative error below 5%, and PSV and PCSV methods revealed relative
errors below 10%. Copyright ? 2009 John Wiley & Sons, Ltd.

KEY WORDS streamflow; point-wise estimation; geostatistical analysis; optimal regional dependency function; point
semi-variogram

Discussion: Fuzzy logic model to predict hydraulic jump, Proceedings of the Institution of Civil Engineers Water Management 163, 98?99

S. Kucukali and S. Cokgor

Contribution by A. Altunkaynak, Istanbul Technical University,
Turkey

In this paper the authors developed a fuzzy logic model to predict hydraulic jump aeration efficiency but parts of the paper appear to be ambiguous, there are points that may need further clarification in both the application of methodology and the results sections.

First, the most important step in developing a fuzzy logic model, which is a kind of blackbox model, is to train and test the model properly. For these operations, the available data are normally split into two parts. While approximately two-thirds of the total data are used for training, the rest of the data are left for testing. The authors of the paper do not appear to have followed this procedure. It may have been better if they had used the training data to determine the fuzzy rule based membership functions of model inputs (Fr1 and Re) and output by considering the least prediction errors and then validated the model using an independent data set such as test data. The absence of these procedures makes the results of the study questionable because it is a well known fact that validating a model with the data that are used at the same time for establishing the model produces high correlations coefficients between observed and predicted values.

A predictive tool by fuzzy logic for outcome of patients with intracranial aneurysm, Expert Systems with Applications, 37(2), 1043-1049.

Hatiboglu M.A., Altunkaynak A., Ozger M., Iplikcioglu A.C., Cosar M., Turgut N., 2010

We aimed to investigate if the outcome of the patients with intracranial aneurysm could be predicted by
fuzzy logic approach. Two hundred and forty two patients with the diagnosis of intracranial aneurysm
were assessed retrospectively between January 2001 and December 2005. We recorded World Federation
of Neurological Surgeons Scale (WFNSS), Fisher Scale and age at admission and Glasgow Outcome Score
(GOS) at discharge from hospitalization for all the patients. We developed fuzzy sets by dividing WFNSS
into four groups as good, fair, bad and very bad; age into three groups as young, middle and old; Fisher
scale into three groups as few, moderate and large; outcome score into four groups as bad, fair, good and
very good. We calculated the outcome of the patient with these sets by fuzzy model. Predicted outcome
by fuzzy logic approach correlated with observed outcome scores of the patients (p > 0, 05), including 95%
confidence interval. We showed that outcome of the patients with aneurysm can be predicted by fuzzy
logic approach, accurately.

Keywords: Fisher scale, Fuzzy logic, Intracranial aneurysm, Outcome score, Prediction

Prediction of specific permeate flux during crossflow microfiltration of polydispersed colloidal suspensions by fuzzy logic models, Desalination, 253 (1-3), 188-194.

Altunkaynak, A. and Chellam S., 2010

Fuzzy logic models for time-variant specific fluxes during crossflow microfiltration of several feed
suspensions under a wide range of hydrodynamic parameters were derived and validated. The coefficient
of efficiency values, which quantifies the degree of agreement between experimental observations and
numerically calculated values were found greater than 0.96 for all cases. An important contribution of this
research is that it is demonstrated that a single robust fuzzy model can quantitatively capture cumulative
effects of a range of particle sizes on membrane fouling. Hence, empirical models incorporating fuzzy logical
operators appear to encompass overall effects of non-linear colloidal transport and deposition mechanisms
as well as changes in cake morphology and resistance with hydrodynamics better than mathematically
complicated mechanistic models. This also suggests the use of fuzzy logic algorithms in programmable
control systems for improved on-site operation of membrane-based liquid–solid separation employed in
municipalities and industries.

Fuzzy system modelling of drinking water consumption prediction,Expert Systems with Applications 36(2009), 11745-11752

Şen Z. , Altunkaynak A. 2009

It is important to determine the amount of daily drinking water requirement for a person not only for the
health of people but also for the planning and management of the water resources. Physical activity, body weight and temperature play significant role in drinking water consumption rates. Human activity variables are most often given in crisp numerical interval classifications for water consumption calculations. The aim of this paper is to establish a fuzzy model for predicting the water consumption rates based on data at the hand. The fuzzy sets such as low, medium, high can be used to quantify vague, imprecise or incomplete descriptions which are collectively referred to as fuzzy data in the literature. Fuzzy model inputs are considered as the physical activity, body weight and temperature, whereas the output is the water consumption levels. The fuzzy sets are chosen in an appropriate manner and the prediction model of water consumption is compared with the actual consumption amounts. It is not possible to treat such linguistic fuzzy data by statistical methods. It is observed that the model predictions have less than 5% relative error. The model is tested with an independent data set for its successful prediction capability.

Keywords: Physical activity, Fuzzy model, Temperature, Uncertainty, Water consumption, Weight