Investigation of Long-Term Monthly Total Streamflow Trends in Bolu City with the IPTAR and IPTA

Yıl 2025, Cilt: 9 Sayı: 2, 231 - 240, 29.12.2025

Onur Arslan

https://doi.org/10.47897/bilmes.1834183

Öz

This study investigates the long-term monthly total streamflow trends in Bolu City by using a new graphical method called Innovative point trend analysis with a radar graph (IPTAR). This method uses the differences between the long-term statistic values to plot a radar graph, a no trend polygon to determine trend directions and critical trend polygons to identify trend significances. Also, the IPTAR was compared with the Innovative polygon trend analysis (IPTA). Bolu is neigbour to Ankara, the capital of Türkiye. It is thought that Ankara water demand up to 2050 can be met via an interbasin water transfer project called the Gerede system on Ulusu Stream. On the other hand, Koprubası Dam is located in Bolu city for the aims of energy production and flood prevention. In this study, long-term streamflow data related to the Gerede system and Koprubası Dam are used for trend analysis. Run test is used to test the homogeneity of data. It is determined that the data are homogeneous within the 99.9 % confidence interval. The IPTAR observed statistically significant decreasing or increasing trends. According to the results of the IPTAR, (1) monthly total flow for April when the highest flow is observed for three stations shows a decreasing trend and the rate of decrease is higher than 10% for two stations. (2) statistically significant increasing or decreasing trends are observed for the monthly total flows for summer months. Comparison of two methods shows that (1) the IPTAR determines trend significance with the critical trend polygons on radar graph while the IPTA assess trends with the trend length and trend slope. (2) trend analysis with the IPTAR is simpler than that of the IPTA due to usage of a radar graph. (3) the IPTAR can start trend analysis from a selected time but the IPTA cannot.

Anahtar Kelimeler

Innovative point trend analysis with a radar graph (IPTAR) , Innovative polygon trend analysis (IPTA) , Trend analysis , Gerede system , Ankara water demand , Koprubası Dam , Bolu

Teşekkür

I would like to thank the State Water Works for providing the data.

Kaynakça

• Z. Şen, “Innovative trend analysis methodology,’’ Journal of Hydrologic Engineering, vol. 17, no. 9, pp. 1042-1046, 2012. DOI: 10.1061/(ASCE)HE.1943-5584.0000556.
• Z. Şen, E. Şişman, and I. Dabanli, “Innovative polygon trend analysis (IPTA) and applications,’’ Journal of Hydrology, vol. 575, pp. 202-210, 2019. DOI: 10.1016/j.jhydrol.2019.05.028.
• Y. S. Guclu, E. Sisman, and I. Dabanli, “Innovative triangular trend analysis,’’ Arabian Journal of Geosciences, vol. 13, p. 27, 2020. DOI: 10.1007/s12517-019-5048-y.
• K. Saplıoğlu, and Y. S. Güçlü, “Combination of Wilcoxon test and scatter diagram for trend analysis of hydrological data,’’ Journal of Hydrology, vol. 612, p. 128132, 2022. DOI: 10.1016/j.jhydrol.2022.128132.
• Z. Şen, “Conceptual monthly trend polygon methodology and climate change assessments,’’ Hydrological Sciences Journal, vol. 66, no. 3, pp. 503-512, 2021. DOI: 10.1080/02626667.2021.1881099.
• Z. Şen, “Innovative trend significance test and applications,’’ Theoretical and Applied Climatology, vol. 127, no. 3-4, pp. 939-947, 2017. DOI: 10.1007/s00704-015-1681-x.
• Y. S. Güçlü, “Improved visualization for trend analysis by comparing with classical Mann-Kendall test and ITA,’’ Journal of Hydrology, vol. 584, p. 124674, 2020. DOI: 10.1016/j.jhydrol.2020.124674.
• A. A. Arra, S. Alashan, and E. Şişman, “Trend of meteorological and hydrological droughts and associated parameters using innovative approaches,’’ Journal of Hydrology, vol. 640, p. 131661, 2024. DOI: 10.1016/j.jhydrol.2024.131661.
• S. Alashan, “Comparison of sub-series with different lengths using şen-innovative trend analysis,’’ Acta Geophysica, vol. 71, pp. 373-383, 2023. DOI: /10.1007/s11600-022-00869-6.
• S. Alashan, A. A. Arra, and E. Şişman, “State-of-the-art visualization for innovative trend analysis,’’ Environmental Earth Sciences, vol. 84, p. 656, 2025. DOI: 10.1007/s12665-025-12643-0.
• T. S. Küçükerdem Öztürk, K. Saplıoğlu, and Y. S. Güçlü, “Median ratio test on graphical representation for trend analysis by comparison with Mann-Kendall and Wilcoxon tests,’’ Hydrological Sciences Journal, vol. 70, no. 14, pp. 2530-2542, 2025. DOI: 10.1080/02626667.2025.2543943.
• O. Arslan, “Innovative point trend analysis with a radar graph (IPTAR) and applications,’’ Theoretical and Applied Climatology, vol. 156, no. 6, p. 328, 2025. DOI: 10.1007/s00704-025-05565-1.
• K. Saplıoğlu, “Comparison of Mann-Kendall Trend Test and Innovative Methods: Beşkonak Monthly Flow Data Example,’’ Journal of Innovations in Civil Engineering and Technology, vol. 6, no. 1, pp. 1-12, 2024. DOI: 10.60093/jiciviltech.1487245.
• R. Acar, “Evaluation of Susurluk Basin Flows Using Trend Analysis Methods,” Firat University Journal of Experimental and Computational Engineering, vol. 3, no. 1, pp. 65-74, 2024. DOI: 10.62520/fujece.1421090.
• C. Köyceğiz, and M. Büyükyıldız, “Comparison of Innovative Trend Analysis Methods for Hydrometeorological Parameters in the Karasu Sub-Basin,’’ Konya Journal of Engineering Sciences, vol. 11, no. 3, pp. 880-893, 2023. DOI: 10.36306/konjes.1291179.
• N. Gupta, and S. R. Chavan, “Assessment of changes in monthly streamflow using innovative polygon trend analysis in the South Indian Rivers,’’ Arabian Journal of Geosciences, vol. 16, p. 657, 2023. DOI: 10.1007/s12517-023-11767-6.
• V. Gumus, Y. Avsaroglu, and O. Simsek, “Streamflow trends in the Tigris river basin using Mann−Kendall and innovative trend analysis methods,’’ Journal of Earth System Science, vol. 131, p. 34, 2022. DOI: 10.1007/s12040-021-01770-4.
• F. Akçay, M. Kankal, and M. Şan, “Innovative approaches to the trend assessment of streamflows in the Eastern Black Sea basin, Turkey,’’ Hydrological Sciences Journal, vol .67, no. 2, pp. 222-247, 2022. DOI: 10.1080/02626667.2021.1998509.
• N. Ahmed, G. Wang, and M. J. Booij, “Changes in monthly streamflow in the Hindukush–Karakoram–Himalaya Region of Pakistan using innovative polygon trend analysis,’’ Stochastic Environmental Research and Risk Assessment, vol. 36, pp. 811-830, 2022. DOI: 10.1007/s00477-021-02067-0.
• A. Y. Özener, “Investigation of hydraulic flow trend and parameters affecting flow of Coruh Basin,’’ M. S. thesis, Recep Tayyip Erdogan University, Rize, 2019.
• T. Özkoca, “Trend analysis of hydrometeorological parameters at Middle Black Sea Region coast band,’’ M. S. thesis, Ondokuz Mayis University, Samsun, 2015.