Sürdürülebilir Kalkınma Amaçları
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- MakaleYalnız künye2026The Trend of Monthly Mean Streamflow Values and Regimes in the Susurluk Basin (Türkiye) with Mountain and Semi-Arid Climates
Yıldız, Mehmet Berkant; Toğrul, Burçe; Kankal, Murat; Akçay, Fatma; Şan, Murat; Nacar, Sinan
This study diagnoses monthly trends in streamflow magnitude and regime for the Susurluk Basin (Türkiye), which spans semi-arid and mountainous sub-climates. Monthly records from 1990 to 2019 were analyzed at 14 stream gauges and nine precipitation stations. Trends are assessed with the Mann–Kendall (MK) test alongside recent graphical approaches, Improved Visualization for Innovative Trend Analyses (IV-ITA) to resolve value class-based (low/high) behavior, and Innovative Polygon Trend Analysis (IPTA) with the Star Concept to quantify intra-annual transitions. Before the trend analyses, the stations were tested to determine whether their values were homogeneous, and any inhomogeneous stations were excluded from the study. The consistency between the trends of nine precipitation stations and the streamflow data in the basin was analyzed. Across the basin, the average streamflow increased by approximately 40–60% between January and March at many measurement points. However, it then decreased by around 80% in April, albeit at a more moderate rate in December. This suggests significant rebalancing occurred during the December–April period, when most of the annual streamflow occurs. IV-ITA exhibits broadly similar trends for both low and high streamflow classes, with notable exceptions in January–February. Precipitation–streamflow trend directions are largely consistent in the high-flow season (December–April), supporting the notion that climatic control influences the detected shifts. To contextualize these signals, basin-wide land-use/land-cover shifts (1990–2018), notably urban growth, forest expansion, and cropland reconfiguration, provide process context, indicating that a larger fraction of rainfall is routed as fast surface runoff while infiltration and base streamflow recharge decline, alongside seasonally modified water demand. Collectively, the MK+IV-ITA+IPTA framework reveals class-specific and intra-annual dynamics that are obscured by monolithic tests alone and provides decision-relevant evidence for allocation, drought–flood risk, and operations in an intensively managed basin.
- MakaleYalnız künye2026Analysis of the Changes in River Water Quality and Quantity with Innovative Trend Methods
Şan, Murat; Nacar, Sinan; Bayram, Adem; Kankal, Murat
This study aims to investigate trends and changes in water quality (WQ) and quantity parameters under low-medium-high groups and seasonal trends employing innovative methods. The data were collected from three monitoring stations in the Broad River Basin (USA). The data spanning the years 1987–2020, on water temperature (WT), dissolved oxygen (DO), discharge (Q), and electrical conductivity (EC) parameters, were used for analysis. A combination of innovative trend analysis with binary segmentation (ITABS) was proposed for objective group separation for the purpose of group trend analysis, allowing for the capture of changes in both location and shape parameters. Recently proposed innovative polygon trend Wilcoxon significance test (IPTWST) and innovative polygon trend analysis (IPTA) were also used to examine seasonal trends for the first time, providing a graphical and qualitative analysis of seasonal behavior. The seasonal Mann-Kendall test was also used to compare them. The ITABS method grouped WQ parameters into more than one group, except for the DO parameter. Especially from EC and Q parameters, it is concluded that the trends in groups do not always contribute to the overall trend or at the same rate. Group trends, therefore, should not be ignored for water resources management. According to IPTA and IPTWST, although there is no clear trend in certain seasons, it is evident that seasonal trends exist, and the Q and EC parameters have a more complex structure. The IPTWST method has the advantage of being able to graphically show the inter-seasonal behavior, although it is identical to the seasonal Mann-Kendall method.
- MakaleYalnız künye2026Monthly precipitation trends in Türkiye under complex topography and varying climate: a seasonal Mann–Kendall and innovative polygon trend framework
Şan, Murat; Nacar, Sinan; Kankal, Murat
The impacts of climate change are increasingly sensible, and Türkiye with its varied topography and diverse climate types is particularly exposed to these shifts. Understanding how precipitation patterns are evolving across its regions is therefore critical. While trend analysis is a widely used tool for this purpose, conventional approaches overlook periodicity, limiting their practical value for water resource management and irrigated agriculture. Therefore, this study aims to examine seasonal trends in long-term (1969–2020) monthly total precipitation in Türkiye, in which each calendar month is treated as a separate season in the sense of seasonal trend-analysis terminology, accounting for altitude, slope, geographical region, and Köppen climate classification. For this purpose, the seasonal Mann-Kendall (SMK) test and the innovative polygon trend Wilcoxon significance test (IPWST), a relatively new graphical method, were used, and the two approaches were comparatively evaluated. According to the study’s results, the rate of increase in coastal areas, specifically the Aegean and Black Seas, exceeds the rate of decrease. In contrast, the reverse is observed in inland and eastern regions. The IPTWST method indicates a more pronounced increasing trend in the Marmara and Mediterranean regions. Furthermore, although analogous trends are observed at lower slopes and altitudes, analyses indicate that these trends are more strongly related to altitude, with the rate of increase decreasing as altitude increases. The IPTWST identified significant or weak trend signals at a larger number of stations than the SMK, particularly in relation to altitude. Nationwide, the two methods revealed significant increases of 7% and decreases of 6%, respectively; this pattern was supported by statistical tests, reflecting the variability of regional climates and the influence of topographic factors on trend analysis.
- MakaleYalnız künye2025Spatial and temporal patterns of drought under different scenarios for Türkiye in the 21st century
Yıldız, Mehmet Berkant; Nacar, Sinan; Şan, Murat; Kankal, Murat
This study investigates the impact of climate change on drought conditions in Türkiye for two distinct future periods: the near future (2021–2050) and the far future (2071–2100), under two emission scenarios (RCP4.5 and RCP8.5). High-resolution regional climate projections from 19 GCM-RCM combinations within the EURO-CORDEX framework were evaluated. Based on performance analysis against ERA5-Land data, the four best-performing models were selected for multi-model ensemble averaging (MMEA). Drought conditions were assessed using the Standardized Precipitation Index (SPI) at 3-, 6-, and 12-month time scales. Three trend analysis methods, Innovative Trend Analysis (ITA), Modified Mann-Kendall (MMK), and Sen's Slope, were applied to examine spatiotemporal drought patterns. SPI-based analyses show a significant increase in short- and medium-term variability (SPI-3 and SPI-6) and long-term droughts (SPI-12), especially in the Central Anatolia, Southeastern and Eastern regions. The applied trend detection methods consistently point to a widespread drying tendency, with more pronounced changes projected in the latter half of the century. Under the RCP4.5 scenario, although the drought signals are less severe, the persistence of negative trends highlights that Türkiye will still be at risk, even with moderate efforts to mitigate climate change. These findings underscore the urgent need for integrating climate-driven drought projections into national and regional planning efforts.
- MakaleYalnız künye2025Analysis of drought in upper Moulouya Basin (Morocco): a combination of drought indices, classic and innovative trend tests
Qadem, Zohair; Hadria, Rachid; Ettaqy, Abderrahim; Kankal, Murat; Şan, Murat; Nacar, Sinan
This study aimed to examine the temporal and spatial variation of drought in the upper Moulouya Basin, Morocco’s arid and semi-arid region. For this purpose, the Standardized Precipitation Index (SPI) was calculated at various time scales (3, 6, 12, and 24 months) using precipitation data collected from eight stations between 1977 and 2019. The data trends were analysed by classical modified Mann-Kendall (MMK) and Innovative Trend Analysis (ITA). Severe drought events were identified in the 1980s, and 1998–2000, while exceptionally wet years were recorded in periods 1996–1997 and 2008–2012. SPI trend analyses revealed a holistic increase on almost all timescales and at all stations. The increase was found to be higher in more extended time scales. Except for a few stations, SPI values in dry, normal, and wet classes of ITA method increased in the second half (1998–2019) compared to the first half (1978–1997). The ITA method detected different trends for different classes at two stations compared to the MMK method. This situation revealed the importance of analysing the trends of different methods in drought studies. These results are essential for water resources management and adaptation to climate change in arid and semi-arid zones.
- MakaleYalnız künye2024Innovative Polygonal Trend Analysis (IPTA) in detecting the seasonal trend behavior of statistically downscaled precipitation for the Eastern Black Sea Basin of Turkey
Nacar, Sinan; Şan, Murat; Kankal, Murat; Okkan, Umut
This study compares projected and past seasonal precipitation trends in the Eastern Black Sea Basin, Turkey. Historical data from twelve stations representing the basin during 1981–2010 was used, while statistically downscaled data from two representative concentration pathway scenarios (RCP4.5 and RCP8.5) outputs of the GFDL-ESM2M general circulation model were utilized for 2021–2050. To determine the seasonal trend behaviors of precipitation variables and transitions between consecutive months, the Innovative Polygon Trend Analysis (IPTA) was implemented. Furthermore, the star concept was employed to illustrate the changing sizes between consecutive periods. Both scenarios showed considerable summer and autumn declines at almost all locations, with low seasonal precipitation variability. These scenarios indicated January to be the important month for trend shift, except for Rize, Pazar, and Hopa stations. The formation of several polygons, polygons intersecting, and polygons not forming on the global regression line show that the hydro-climatic cycle might be chaotic.
- MakaleAçık Erişim2024Trends and amount changes of temperature and precipitation under future projections in high–low groups and intra-period for the Eastern Black Sea, the Wettest Basin in Türkiye
Nacar, Sinan; Şan, Murat; Kankal, Murat; Okkan, Umut
This study investigates the possible effects of climate change on temperature and precipitation variables in the Eastern Black Sea Basin, Türkiye’s wettest and flood-prone region. The outputs of three GCMs under historical, RCP4.5, and RCP8.5 scenarios were downscaled to regional scale using the multivariate adaptive regression splines method. The future monthly temperature and precipitation for 12 stations in the basin were projected for three periods: the 2030s (2021–2050), 2060s (2051–2080), and 2090s (2081–2100). In addition to relative changes, high and low groups and intra-period trends were analyzed for the first time using innovative methods. For the pessimistic scenario, an increase of 3.5 °C in the interior and 3.0 °C in the coastal areas of the basin is projected. For the optimistic scenario, these values are expected to be 2.5 and 2.0 °C, respectively. A decrease in precipitation is projected for the interior region, and a significant increase is expected for the eastern and coastal areas of the basin, especially in spring. This result indicates that floods will occur frequently coastal areas of the basin in the coming periods. Also, although the monotonic trends of temperatures during periods are higher than precipitation in interior regions, these regions may have more uncertainty as their trends are in different directions of low and high groups of different scenarios and GCMs and contribute to all trends, especially precipitation.
- MakaleYalnız künye2024Spatiotemporal analysis of transition probabilities of wet and dry days under SSPs scenarios in the semi-arid Susurluk Basin, Türkiye
Şan, Murat; Nacar, Sinan; Kankal, Murat; Bayram, Adem
Precipitation, especially in regions dominated by the Mediterranean climate, is one of the most critical parameters of the hydrological cycle and the environment affected by climate change. One the one hand, the transition probabilities of wet and dry days in precipitation occurrence are a relatively new topic, on the other hand these are essential in defining the regional climate. For the first time, spatiotemporal variations of transition probabilities of wet and dry days in the Susurluk Basin, northwestern Türkiye, dominated by a semi-arid Mediterranean climate and also having a mountain climate, were analyzed based on the observation (1979–2014) and future terms (2030–2059 as short and 2070–2099 as long), under four Shared Socioeconomic Pathways (SSPs) scenarios. To do this, statistical downscaling was performed for 14 general circulation models (GCMs) from the CMIP6. By applying an ensemble of four high-performing GCMs, four indices for transition probabilities of wet and dry, i.e., a dry day following a dry day (FDD), a wet day following a dry day (FDW), a dry day following a wet day (FWD), and a wet day following a wet day (FWW), were calculated, and their changes were determined statistically. Monotonic and partial trends of the indices were also analyzed. According to the results, the FDD will increase in water year and wet period and autumn in the future, especially for the long term, in the basin dominated by the FDD (75 % in water year). The risks are higher in the western part of the basin, where human activities are intense, as the FDD is higher in this part than other parts especially in summer (90–100 %) in SSP3-7.0 and SSP5-8.5 scenarios for the long term. So, the length of consecutive dry days in the wet period and water year will increase in the basin, thus increasing the likelihood of droughts. As for the intra-term trends, the FDD increases and the FWW decreases in the water year and seasons in SSP3-7.0 and SSP5-8.5, contrary to the observation term.
- MakaleYalnız künye2023Trend analysis of precipitation using innovative approaches in northwestern Turkey
Körük, Ali Emre; Kankal, Murat; Yıldız, Mehmet Berkant; Akçay, Fatma; Şan, Murat; Nacar, Sinan
Precipitation is highly sensitive to climate change, and monitoring its trends over time is essential for understanding the effects of global warming on the Earth's water cycle. This study investigates the effects of climate change on monthly precipitation in the Susurluk Basin located in northwestern Turkey, using innovative trend analysis methods. Innovative Polygon Trend Analysis (IPTA) using star graphics and Improved Visualization for Innovative Trend Analysis (IV-ITA) techniques were used to analyze precipitation data from nine stations in the basin over 50 years (1970–2019), and the findings were compared to classical Mann-Kendall (MK) results. According to the trend analysis results, the MK method detected significant trends in only two months in the decreasing direction. In these decreasing trends observed at Simav and Keles stations in November, z values were calculated as −2.38 and −2.05, respectively. IPTA method detected increasing trends in 54 months and decreasing trends in 40 months; this means there is a change of more than 5% between two half series. The IV-ITA method indicated an increase of more than 40% in the low values for January, March, August, and September. In addition, there was an increasing trend of more than 40% in the high values observed in September at all stations. It was observed that mean precipitation heights increased from September to December and then decreased throughout the basin. It is predicted that decreases in precipitation during dry seasons may put intense pressure on agricultural water use and affect water quality. In addition, the increase in precipitation in spring months may increase flood events. It was determined that graphical innovative trend analysis methods are more effective in trend identification than MK, and these methods' results have much higher visual inspection and linguistic interpretation possibilities. Innovative methods allow for more flexible and in-depth analysis using different statistical parameters.
- MakaleAçık Erişim2023Daily precipitation performances of regression-based statistical downscaling models in a basin with mountain and semi-arid climates
Şan, Murat; Nacar, Sinan; Kankal, Murat; Bayram, Adem
The impacts of climate change on current and future water resources are important to study local scale. This study aims to investigate the prediction performances of daily precipitation using five regression-based statistical downscaling models (RBSDMs), for the first time, and the ERA-5 reanalysis dataset in the Susurluk Basin with mountain and semi-arid climates for 1979–2018. In addition, comparisons were also performed with an artificial neural network (ANN). Before achieving the aim, the effects of atmospheric variables, grid resolution, and long-distance grid on precipitation prediction were holistically investigated for the first time. Kling-Gupta efficiency was modified and used for holistic evaluation of statistical moments parameters at precipitation prediction comparison. The standard triangular diagram, quite new in the literature, was also modified and used for graphical evaluation. The results of the study revealed that near grids were more effective on precipitation than single or far grids, and 1.50° × 1.50° resolution showed similar performance to 0.25° × 0.25° resolution. When the polynomial multivariate adaptive regression splines model, which performed slightly higher than ANN, tended to capture skewness and standard deviation values of precipitations and to hit wet/dry occurrence than the other models, all models were quite well able to predict the mean value of precipitations. Therefore, RBSDMs can be used in different basins instead of black-box models. RBSDMs can also be established for mean precipitation values without dry/wet classification in the basin. A certain success was observed in the models; however, it was justified that bias correction was required to capture extreme values in the basin.
- MakaleYalnız künye2023Annual Trends of Precipitation and Temperature in the Northwestern Part of Turkey Using Innovative Approaches: A Holistic and Partial Study
Akçay, Fatma; Şan, Murat; Nacar, Sinan; Kankal, Murat
Trend analysis benefits collecting and analyzing reliable data in climate change studies. In this context, long-term temperature and precipitation data analysis, two variables sensitive to climate change, is essential. This study aims to holistically and partially determine the annual trends of precipitation and temperature time series for 1970–2019 at nine selected stations in the Susurluk Basin, Turkey. The innovative trend significance test (ITST), innovative crossing trend analysis (ICTA) method, and Mann-Kendall (MK) test were used to determine holistic trends. Also, partial trends were determined using successive average methodology (SAM). For the precipitation variable, while an increasing trend was determined for the ITST, there was mostly no trend for the other methods. While a strong increasing trend was detected for the temperature according to the ITST and MK methods, no trend was observed in any station according to the ICTA method. According to the SAM results, the maximum trend durations for the peak and trough change points were 4.9 (10.3) and 5.3 (8.4) years, respectively, for precipitation (temperature). The strong temperature trends in the basin will likely continue, requiring precautions against extreme events such as drought.
- MakaleYalnız künye2022Farklı İklim Değişikliği Senaryoları için Doğu Karadeniz Bölgesindeki Meteorolojik Kuraklıkların Eğilim Analizi
Kankal, Murat; Nacar, Sinan; Okkan, Umut; Şan, Murat
Kuraklık diğer doğal afetlerden farklı olarak gelişimi daha uzun zaman alan ve etkileri daha uzun süre devam eden bir afettir. Meydana gelmesi muhtemel bir kuraklığın önceden belirlenmesi, kuraklığın olumsuz etkilerinin daha etkili bir şekilde azaltılmasını mümkün kılmaktadır. Standartlaştırılmış Yağış İndeksi (SYİ) farklı iklim koşullarına sahip, farklı zaman dilimleri ve bölgeler arasındaki kuraklıkları tanımlamak için en sık kullanılan kuraklık indeksidir. Bu çalışmanın amacı almış olduğu yağış miktarı bakımından Türkiye’nin en önemli hidrolojik havzalarından biri olan Doğu Karadeniz Havzası’nın (DKH) geçmiş ve gelecek dönem kuraklık analizini SYİ parametresi ile gerçekleştirmek ve bu parametrenin eğilimini belirlemektir. Bu kapsamda DKH içinde ve çevresinde yer alan 12 meteoroloji istasyonundan ölçülmüş olan 1981-2010 dönemi aylık toplam yağış verileri kullanılarak SYİ değerleri hesaplanmıştır. Ayrıca CMIP5 arşivinde yer alan GFDL-ESM-2M genel dolaşım modelinin iyimser (RCP4.5) ve kötümser (RCP8.5) senaryolar altındaki bölgesel ölçeğe indirgenmiş olan 2021-2050 dönemi çıktılarına da aynı işlemler uygulanmıştır. Meteorolojik kuraklığın eğilim analizleri için 1 ve 3 aylık SYİ değerleri üzerinde Yenilikçi Eğilim Analizi yöntemi kullanılarak üç farklı grupta ve %95 güven düzeyinde tekdüze olarak eğilim analizi gerçekleştirilmiştir. Gözlem değerlerinde ve RCP senaryolarında istasyonların yaklaşık %25’inde şiddetli yağışlarda ve şiddetli kuraklıklarda artış görülmüştür. Ancak SYİ değerlerinde geçmiş dönem periyodunda Akçaabat istasyonu (azalan eğilim) hariç tekdüze anlamlı artan eğilim görülürken gelecek dönem periyodunda her iki senaryo için azalan yönde eğilim görülmüştür.