Sürdürülebilir Kalkınma Amaçları

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• MakaleYalnız künye2026Scopus SJRQ2/r/munzur/1525
  An Investigation of the Variability of Short-Term Drought with SPEI-Based Severity, Duration and Magnitude Parameters in a Transboundary Basin

  Akbas, Ergun; Acar, Ramazan; Eşit, Musa; Koycegiz, Cihangir

  Climate change-induced variability in the water budget leads to significant drought events. In this study, severity, duration, and magnitude parameters obtained from 1-month and 3-month series of the Standardized Precipitation Evapotranspiration Index (SPEI) were used to investigate short-term drought from different perspectives. The lower part of the Euphrates-Tigris Basin, which is a transboundary basin, was preferred as the study area within the borders of Türkiye. In this study, monthly total precipitation and monthly mean temperature data for the period 1963–2021 were used. Both graphical (Şen Innovative Trend Analysis) and statistical (Mann–Kendall, Spearman’s Rho, Sen’s Slope Estimator) trend analysis methods were applied to detect, categorize, and analyze the variability of drought. The Combination of Wilcoxon Test and Scatter Diagram (CWTSD) method, which offers both graphical and statistical trend analysis capabilities, was preferred to enhance consistency and facilitate comparison of results. According to the findings, more severe droughts are observed in the eastern part of the basin compared to the western part. Across the basin, severity and magnitude are decreasing, while duration is increasing. The increase in duration indicates that droughts are shifting from short-term to long-term periods. This situation is of great importance in terms of planning agricultural strategies.

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  AtıfOpenAlex3

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• MakaleAçık Erişim2026Scopus SJRQ2/r/munzur/1494
  Local Scour Process in Conduit Aerated Water Jets

  Tuna, M. Cihat; Acar, Ramazan; Tunç, Mustafa

  High-velocity water jets emerging from hydraulic structures cause local scouring in downstream areas, creating significant risks to structural safety. In this study, the effects of natural aeration provided through pressurized pipes on jet-induced scouring were investigated through laboratory experiments. A total of 60 experiments were conducted for different gate openings, flow rates, and downstream water levels; the scour geometries created by aerated and non-aerated jets were compared. The aeration level was defined by the dimensionless air-to-water flow ratio (Qa/Qw); maximum scour depth, scour length, scour slope angle, and jet fall distance were considered as basic evaluation parameters. The experimental results showed that increased aeration significantly reduced the maximum scour depth and scour length while moving the point of contact of the jet further upstream. While the scour depth and slope angles reached their highest values in non-aerated jets, shallower and flatter scour profiles were formed in aerated conditions. An empirical relationship predicting the maximum scour depth using experimental data has been developed and found to be in high correlation with the measured values (R2 = 0.93). The findings reveal that channel aeration is an effective method for reducing scouring and demonstrate that this approach can be considered a safe and economical alternative in the design of spillways, wastewater treatment plants, and similar hydraulic systems.

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• MakaleAçık Erişim2026Scopus SJRQ1/r/munzur/1335
  The effect of hydrostatic water level on the local scour downstream of plunging aerated jets

  Tunc, Mustafa; Aytac, Ayca; Tuna, M. Cihat; Acar, Ramazan

  This paper reports an experimental study on the effect of hydrostatic water level on local scour downstream of plunge aerated jets. To examine the shape of the scour for non-cohesive bed material, different flow and air rates, and different aeration capabilities, hydrostatic water level circumstances were tested. The water jets were aerated using conduit systems with varying cover opening ratios. Measurements were made to determine the length of the scour hole, the value of the maximum scour depth, the location of the maximum scour depth, and the scour hole profile in equilibrium. The current findings show that downstream hydrostatic water levels have a significant impact on the maximum depth and area of scour. Additionally, it was discovered that the conduit gate opening ratio and aeration performance (Qa/Qw) are crucial factors that affect the geometry and diameters of scour holes. The properties of scour caused by various hydrostatic levels were systematically compared to develop empirical correlations for predicting the maximum scour depth. Consequently, predictive emprical formulas incorporating these hydrostatic variations and aeration parameters are presented to improve engineering design accuracy.

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• MakaleAçık Erişim2026Scopus SJRQ2/r/munzur/1158
  Using Decision Tree and K-Means to Improve ANFIS for Predicting Missing Flow Data in Çoruh Basin

  Acar, Ramazan

  Complete and continuous flow data provides contributions to the water resources projects appropriate design. However, both financial and technical factors prevent the regular collection of data and such a situation leads to missing data problems. Input variables are from five stations in the Çoruh Basin in the northeast province of Türkiye, and output variables are from one station. In the study, 75% (171 months of data) of the 228 months flow data between the years 1993–2011 are used in the training phase and 25% (57 months of data) in the testing phase. In the ANFIS models, Decision Tree (DT) and K-means (KM) methods are used in selecting the input variables and determining the number of membership functions. In addition, artificial neural network (ANN), multiple linear regression (MLR), and ANFIS models with randomly determined cluster numbers are also used to compare the model performance of these methods. The results show that using DT and KM methods, the ANFIS models generate more reliable results than other models. During the study, the regression coefficient (R2), weighted mean square error (WMSE), and Wilcoxon (Z) values are taken into account for reliability measure. The DT–K-means–ANFIS model achieved the highest accuracy with R2 = 0.98 and WMSE = 5.89 during the testing phase, demonstrating superior performance to the ANN and MLR models. It is shown that the most successful models can be determined in a shorter time by using DT and KM methods before generating ANFIS models.

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  AtıfScopus1·WoS1·OpenAlex1

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• MakaleAçık Erişim2026Scopus SJRQ1/r/munzur/725
  Optimization of scours downstream of conduit aerators

  Arici, Erdinc; Tuna, M. Cihat; Aytac, Ayca; Acar, Ramazan; Tunc, Mustafa

  Dams, wastewater treatment plants, and aquaculture areas often require aeration, making it crucial for hydraulic engineers to predict the physical properties of scour holes occurring on the downstream side of conduits. Conduit systems that provide high aeration performance necessitate multiple optimization studies to simultaneously maximize the scour parameters and the system’s physical properties. In this study, the physical parameters of conduit systems and downstream scour parameters were optimized using Artificial Neural Networks (ANN). The optimum system parameters were identified based on the experimental results through ANN-based optimization. Additionally, the real and optimal effects of the parameters on aeration performance and scour were determined. The results of the study demonstrated that ANN can be effectively used in studies aimed at optimizing the aeration performance and scour values of conduits. This study is the first to apply ANN for the simultaneous optimization of both aeration efficiency (Qa/Qw) and scour characteristics (dmax and δ) in a conduit-based hydraulic system. Previous studies have typically focused on either scour or aeration individually; this study integrates both through a multi-objective ANN model. The findings provide novel insights for the design and retrofitting of energy-dissipating conduit structures in high-head dam applications. Unlike traditional empirical or regression-based approaches, the ANN model captures complex, nonlinear relationships among multiple interacting hydraulic variables. It identified optimal parameter combinations — such as 70% gate opening, 1.30–1.50 m conduit length, and 9 mm air hole diameter — that improve both aeration and scour behavior. These outcomes offer direct applicability for real-world hydraulic system optimization.

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  AtıfOpenAlex1

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• MakaleAçık Erişim2025/r/munzur/6181
  Su Kalitesi Parametreleri için Mann-Kendall ve Yenilikçi Trend Yöntemlerinin Karşılaştırılması

  Acar, Ramazan

  Günümüzde farklı veri setleri (su kalitesi, akım, yağış, sıcaklık vb.) ile eğilimlerin tespit edilmesi için pek çok yöntem mevcuttur. Bu çalışmada trend analizi çalışmalarında yaygın bir şekilde kullanılan Mann-Kendall (MK) test istatistiği ile Spearman Rho test istatistiği ve son yıllarda popüler hale gelmiş olan Şen’in yenilikçi trend yöntemi (ITA), Yenilikçi eğilim çözümlemesi için geliştirilmiş görselleştirme (IV-ITA) yöntemlerinin performansları karşılaştırılmıştır. Bu amaçla Akdeniz Bölgesi’nde yer alan Ceyhan Nehri’ne ait 20-06-00-001 numaralı istasyonundan alınan 1986-2013 su yıllarına ait yıllık ortalama ve mevsimlik ortalama 8 adet su kalitesi parametresi kullanılmıştır. Öncelikle her bir parametrenin değerleri YSKYY’nde verilen su kalite değerleriyle karşılaştırılmış ve her bir parametreye göre su kalitesi sınıfları belirlenmiştir. Daha sonra her mevsim kendi içinde ve yıllık ortalama değerlerin trendleri karşılaştırılmıştır. Bu nedenle 5 farklı trend testinin karşılaştırılması yapılmıştır. Ancak sırasıyla yapılmış olan homojenlik ve otoregresif korelasyon testi işlemlerine göre hem %95 güven aralığında homojen olmayan hem de korelasyon değeri 0.30’un üzerinde kalan bazı veriler kıyaslamada kullanılmamıştır. Makalede elde edilen sonuçlar değerlendirildiğinde farklı analizlerin birlikte yapılarak kullanılması testlerdeki yanılma payını azaltacağı kanısına varılmıştır.

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  AtıfOpenAlex3

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• MakaleYalnız künye2025Scopus SJRQ1/r/munzur/1413
  Median-Linear model for solar radiation estimation by comparison with ANFIS and Angström-Prescott methods

  Acar, Ramazan; Saplıoğlu, Kemal; Güçlü, Yavuz Selim

  This paper aims to propose a novel approach to estimating solar radiation in relation to sunshine duration. A hybrid Median-Linear (MedLin) model is presented including both the median value and the linear solar radiation equation. First stage is concerned with two-stage alternative of the proposed model with inputs and outputs exhibiting a seasonality structure and it is seasonally adjusted using median values. In the second stage, the linear equation for the difference values is determined with estimations the difference in solar radiation. Finally, the median value and the estimated difference value are added. Monthly total solar radiation values are estimated using monthly total sunshine duration data from Mardin, Adana, Bozova, Hakkari, Şırnak, and Van stations in Southeast of Türkiye for the application. The predictions of the MedLin approach are compared with the results of the Angström-Prescott, ANFIS, and Mean-Linear (MeanLin) models. As for the prediction of monthly total solar radiation data at Mardin and Hakkari stations, the proposed MedLin approach yields the best results compared to other methods with mean absolute percentage error 3.508% and 8.951%, respectively. Angström-Prescott model for Adana, MeanLin method for Bozova, ANFIS model for Şırnak, and MeanLin model for Van provided the best predictions with mean absolute percentage error 3.721%, 3.285%, 4.278%, and 13.101%, respectively. The results show that the MedLin technique proposed in this paper is useful for solar radiation estimation.

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  AtıfWoS1

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• MakaleYalnız künye2025Scopus SJRQ1/r/munzur/1276
  Rainfall trends in the transboundary Euphrates-Tigris River Basin

  Acar, Ramazan; Akbas, Ergun; Koycegiz, Cihangir; Esit, Musa

  Climate change and anthropogenic factors have a significant impact on rainfall variability. In this study, the trends of monthly total precipitation in the transboundary Euphrates-Tigris River Basin (ETRB), where these effects are intensely observed, were analyzed by trend analysis methods with various perspectives. After decomposing the monthly total rainfall series (1964–2021) obtained from 18 stations representing 12 months of the year, statistical (Mann-Kendall, Wilcoxon, Onyutha), graphical (Innovative Polygon Trend Analysis, IPTA), Trend Polygon Star Concept, TPSC), sub-trend (Onyutha) and spatial trend analyses were performed. Based on the results, it was observed that rainfall in the basin has significant spatial and temporal variability. A monotonic strong decreasing trend was observed in cold months with high rainfall, while an increasing trend was observed in warm months with low rainfall. Extreme rainfall during the winter months has shifted towards the end of the cold months. Graphical and statistical analysis methods have shown strong consistency in identifying monotonic trends. However, the implementation of various methods provides specific insight (transition, sub-trend, etc.) into the temporal and spatial variability of rainfall. Sub-trend analysis shows that rainfall characteristics in the cold months show a significant change before and after the 1990–2000 period. In warmer months, this variability is significantly affected by local and global driving forces. The central and marginal parts of the ETRB have different rainfall characteristics. During cold months, the monotonic trend (decreasing) is significant in the central part. In warm months, the monotonic trend (increasing) increases its intensity in the eastern parts.

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  AtıfScopus12·WoS10·OpenAlex14

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• MakaleYalnız künye2025Scopus SJRQ2/r/munzur/924
  Using Meta-Heuristic Optimization Algorithms to Determine Baseflow and Comparing Their Temporal Performance

  Acar, Ramazan; Sapliogu, Kemal

  Accurate and simple determination of baseflow is an extremely important issue. In this study, the baseflow levels of Göksu station number 1805 in the Seyhan basin were determined by calibrating the Lyne and Hollick, Chapman, Chapman and Maxwell methods available in the literature using meta-heuristic optimization methods. The meta-heuristic algorithms used for calibration in the study were run thirty times each. Thus the reliability, the reliability of the algorithms was tested with the standard deviations obtained. The study also measured the temporal performance of the algorithms. In addition, the baseflows of Göksu station were determined and their percentage rates were found separately according to all three methods and intuitive methods, and the results obtained were compared. By examining the results obtained in this section, the average baseflow rate of the basin was also determined. Furthermore, each phase of the study was repeated over a five-year period, with the objective of measuring its sustainability. Consequently, it has been demonstrated that the method can be employed over extended periods.

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  AtıfOpenAlex1

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• MakaleYalnız künye2025Scopus SJRQ1/r/munzur/882
  Seasonally adjusted periodic time series for Mann-Kendall trend test

  Güçlü, Yavuz Selim; Acar, Ramazan; Saplıoğlu, Kemal

  In this study, temperature data trend analysis is conducted, which is thought to be influenced by global warming, climate change, and local factor impacts. The main objective of this paper is to obtain an acceptable autoregressive correlation value for the MK test. For this purpose, seasonality (periodicity) especially in monthly time series is adjusted. Autoregressive correlation and homogeneity test values decrease after seasonal adjusting, but reasonable results are not achieved. Then, prewhitening procedure is also applied to the seasonally adjusted data. This process resulted in the data becoming both homogeneous and free autoregressive correlation. The final version of the time series is suitable for the MK test. Furthermore, the time series are divided into different time intervals, and the efficacy of the method is investigated. The results demonstrated that the method is suitable for time series with less than 30 years of data. The study demonstrated that the proposed method enhances the reliability of the data. Also, multiplication by 12 (months) allows the MK test with Z score in place of the Student's t-test in short-term data sets. This suggested methodology can be used to identify MK trend conditions in monthly time series. The application is based on monthly and annual average temperature data between 1957 and 2022 from three stations within the Kızılırmak basin (Çankırı, Kırşehir, Sivas stations) and one station within Seyhan Basin (Adana station) in Türkiye. The test results exhibited a significant increasing trend.

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  AtıfScopus37·WoS34·OpenAlex41

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