Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Hydrological Insights From SWOT: Comparative Analysis of Water Surface Elevation and Area Time Series From Hydrocron API(Elsevier, 2025) Karahan, Sait Mutlu; Gunduz, OrhanThe Surface Water and Ocean Topography (SWOT) mission plays an essential role in enhancing the monitoring and management of inland water bodies by providing high-resolution global observations of surface water dynamics. A critical tool in leveraging SWOT data is the Hydrocron API (Application Programming Interface), which facilitates access to temporally consistent SWOT-derived hydrological datasets. In this study, SWOT's Lake data "L2_HR_LakeSP" time series data retrieved from Hydrocron was utilized to evaluate water surface elevation (WSE) and surface area dynamics across six distinct lake locations around the world. To quantify the accuracy of SWOT, error metrics including Symmetric Mean Absolute Percentage Error (SMAPE), Absolute Percentage Error (APE), and Normalized Root Mean Square Error as a percentage (NRMSE%) were computed for both WSE and surface area estimates. The results indicated that the highest WSE error, with a SMAPE of 3.83 %, was observed in the lake characterized by the smallest surface area, suggesting a sensitivity of SWOT measurements to spatial scale. Conversely, the greatest error in surface area estimation occurred in the shallowest lake with SMAPE and APE values of 19.56 % and 22.01 %, respectively, highlighting the influence of bathymetric complexity on SWOT's detection capabilities. Despite these localized variances, the overall performance of SWOT data was found to be highly promising, demonstrating strong potential for operational hydrological applications and long-term water resource monitoring. The integration of SWOT observations with hydrological models via platforms such as Hydrocron underscores the mission's potential in advancing the understanding of inland water dynamics at both regional and global scales.Article Nature-Based Solutions in Island Water Management: A Case Study From Bozcaada (Türkiye)(Academic Press Ltd- Elsevier Science Ltd, 2025) Samiloglu, Bilgesu; Baba, Alper; Cuevas, Raquel Marijuan; Gunduz, OrhanNature-based Solutions (NbS) are increasingly recognized for their role in the sustainable management of water resources, especially in Mediterranean regions facing seasonal water scarcity. While their benefits for biodiversity and climate resilience are well documented, there is little research on their application in small island regions where ecological fragility and water scarcity intersect. This study fills this gap by investigating the potential of NbS, particularly rainwater harvesting systems, on the island of Bozcaada (T & uuml;rkiye). A high-resolution Digital Elevation Model (DEM) was developed to delineate the watersheds of the island and analyze the water flow patterns. These watersheds were analyzed for their water retention potential and suitability for rainwater storage. The geological structure, soil type and native biodiversity were included in the site selection process to ensure ecological compatibility. Based on this analysis, optimal locations for ponds were identified and designed to support groundwater recharge and preserve local ecosystems. The results show that strategically placed rainwater ponds can improve seasonal water availability, reduce dependence on external sources and support native species throughout the year. This NbS-based approach provides a replicable framework for sustainable water management on small Mediterranean islands, emphasizing ecological integration and long-term resilience.Article Citation - WoS: 1Citation - Scopus: 1Microplastic Pollution and Risk Evaluation in the Gediz River(Central Fisheries Research inst, 2026) Baycan, Neval; Alyuruk, Nefise; Kazanci, Yigithan; Alpergun, Cumana; Kara, Nursena; Gunduz, OrhanMicroplastics (MPs), particles less than 5 mm in diameter, enter the aquatic ecosystem through the degradation of larger plastics. They can accumulate in the environment for long periods due to their durability and buoyancy. In this study, a risk assessment of MPs was conducted at five different stations in the Gediz River via a Pollution Load Index (PLI) and a Polymer Hazard Index (PHI) calculated for dry and wet seasons to highlight the risks caused by seasonal variations of pollution levels for different types of MPs in an urban river discharging to Izmir Bay. The results showed that MPs were widespread in the area, with an average abundance of 13-211 units/L/L. During the dry season, the mean number of particles was 67 +/- 57; during the wet season, the mean number of particles decreased to 50 +/- 37. The most common type was polypropylene with 62.4%, followed by Polyethylene and Polyethylene Terephthalate (8.3% and 7.01%). The most abundant MP shapes are fragments and fibers, with 47.1% and 38.5%. During the dry season, PLI values ranged from 0.99 to 2.44, while in the wet period, they ranged from 1.08 to 2.11. Furthermore, PHI values for the MP species detected at each station ranged from 3.81 to 7.91. The results indicated that the Gediz River is a significant MPs source for Izmir Bay and demonstrates a major hazard for its overall ecological condition.Article Effects of Industrial and Domestic Wastewater Treatment Plants on Microplastic Pollution in an Urban River in Türkiye(Springer int Publ Ag, 2025) Baycan, Neval; Alyuruk, Nefise; Kazanci, Yigithan; Alpergun, Cumana; Kara, Nursena; Tasdelen, Ozge; Gunduz, OrhanMicroplastic (MP) contamination in inland aquatic systems is a growing environmental concern due to its persistence and potential ecological impacts. This study provides a comprehensive assessment of the occurrence, composition, and seasonal dynamics of MPs in two urban rivers-Nif Creek and Gediz River-in western T & uuml;rkiye, which receive treated and untreated effluents from domestic and industrial wastewater treatment plants (WWTPs). A total of 20 river water and 3 sediment sampling stations were monitored across four seasons. MP concentrations ranged from 7 to 146 particles/L in water and from 9,867 to 136,177 particles/kg in sediments, with the highest abundances observed near WWTP outfalls and urban infrastructure. Polypropylene was the dominant polymer in water (59.1%) and WWTP effluents (44.4%), while polyethylene was most prevalent in sediments (60.2%). MPs were primarily within the 0.1-0.5 mm size range and were predominantly transparent in colour. Statistical analyses indicated significant positive correlations between MP abundance and key water quality parameters, including chemical oxygen demand, total suspended solids, and selected heavy metals (e.g., Zn, Cd, Ni). The polymeric composition of MPs reflected both urban and industrial sources, with variations in polymer profiles linked to spatial and seasonal factors. Compared to values reported in European freshwater systems, MP levels in the studied rivers were considerably higher, underscoring the need for improved wastewater management and targeted monitoring efforts in urban river basins.Article An Experimental Study on Microplastic Settling Velocities in Different Water Environments: Which Factors Shape the Settling Process(Pergamon-Elsevier Science Ltd, 2025) Alpergun, Cumana; Alyuruk, Nefise; Baycan, Neval; Gunduz, OrhanUnderstanding the behavior of microplastics in aquatic environments is crucial, given their widespread presence and potential ecological impact. This study investigated the effects of biofilm formation and weathering processes on the settling rates of microplastics across different water matrices. To this end, nine different polymer types were examined in four distinct conditions-pristine, biofilm-coated, aged, and biofilm-coated after weathering-across three defined size categories. A total of 648 experimental results representing different conditions were analyzed. The results revealed that the settling velocities of microplastics ranging from 0.5 to 4.5 mm varied between 0.012 and 0.154 m/s. Polybutylene terephthalate and polyethylene terephthalate particles exhibited the fastest settling rates (0.154 and 0.145 m/s), whereas acrylonitrile butadiene styrene showed the slowest (0.012 m/s). Although microplastic density and size were found to be significant factors of settling velocity, water matrix, biofilm formation, and weathering processes did not show a statistically significant difference under the conditions of this study. This was related to insufficient time for biofilm growth, limited structural changes due to weathering, and the controlled laboratory environment. Biofilm formation was observed to be more pronounced on rough and matte surfaces, while it was less prominent on shiny and slippery surfaces. Additionally, it was determined that weathering alters surface morphology and potential adsorption capacity, which plays a critical role in the environmental interactions of microplastics. Furthermore, the experimentally determined settling velocities were compared with theoretical estimations obtained using two different models from the literature. A comparison between the experimental settling data and theoretical models demonstrated a strong alignment with the models proposed by Waldschla<spacing diaeresis>ger and Sch & uuml;ttrumpf (2019) and Akdogan and Guven (2024), particularly for microplastics with irregular shapes. These results suggest that such theoretical approaches can reliably predict the settling behavior of specific polymer types. Overall, the findings underscore the practical applicability of these models for estimating the transport and fate of microplastics in natural aquatic systems, offering a valuable foundation for future environmental assessments.Article Citation - WoS: 7Citation - Scopus: 9A Holistic Overview of the Applications of Grace-Observed Terrestrial Water Storage in Hydrology and Climate Science(Springer, 2025) Khorrami, Behnam; Gunduz, OrhanTerrestrial Water Storage (TWS) represents a vital element of the hydrological cycle, with its fluctuations significantly impacting the climate of the Earth and its ecological balance. Since its launch in 2002, the Gravity Recovery and Climate Experiment (GRACE) satellite mission has revolutionized the ability to observe and analyze large-scale mass changes within Earth's system components. This paper offers a comprehensive and current overview of GRACE satellite gravimetry, highlighting its relevance to hydrological and climate-related studies. It outlines the fundamental measurement principles of the GRACE mission, provides an in-depth explanation of GRACE data products (including spherical harmonic and mascon solutions), examines emerging trends in GRACE-based research, and reviews key applications in hydrology and climate science. Additionally, it addresses the major challenges in utilizing GRACE data and explores promising avenues for future research and applications.Article Citation - WoS: 3Citation - Scopus: 3Analysis of Microplastic Flux From the Gediz River To the Aegean Sea: a Modeling Study for Environmental Management(Academic Press Ltd- Elsevier Science Ltd, 2025) Kazanci, Yigithan; Alyuruk, Nefise; Alpergun, Cumana; Kara, Nursena; Baycan, Neval; Gunduz, OrhanIt is critical to determine the abundance of microplastics in terrestrial inland waters, understand their fate and transport mechanisms, and reveal their status in aquatic environments. This study aimed to develop and calibrate a mathematical model to simulate microplastic (MP) pollution in the Gediz River Basin, T & uuml;rkiye, which focused on MP fate and transport under existing conditions and various management scenarios. The baseline scenario revealed that, despite a ninefold difference in flow rates, the midstream and upstream parts of the basin also exhibited significant contamination, with an average concentration of 25 n/L compared to the downstream average of 29 n/L. The model was later simulated to test the effects of various mitigation scenarios including but not limited to reducing MP discharges from wastewater treatment plants (WWTPs) and implementing vegetative barriers in tributaries. Scenario 4, which involves reducing MP concentrations in upstream tributaries with vegetative barriers, achieved the highest average reduction across all segments (32 %) and specifically in the downstream area (47 %). In contrast, Scenario 1, aimed at reducing wastewater discharges from urban and industrial WWTPs through water reclamation, and Scenario 2, which focused on eliminating MP in Organized Industrial Zone (OIZ) discharges by changing industrial inputs, achieved the most effective MP reductions in the upper basin, with reductions of 20 % and 17 %, respectively. Scenario 3, targeting flow reduction and accumulation through constructed wetlands, had minimal impact, with reductions close to 0 % in most areas. These results highlight the need for comprehensive approaches to effectively reduce MP pollution, particularly in managing upstream and tributary sources.Article Citation - WoS: 1Derivation of Soil Hydraulic Properties (SHPS) Using a Physics-Based Inverse Calibration Method and International Soil Moisture Network Database(Elsevier, 2025) Sahin, Onur Gungor; Gunduz, OrhanThis study used extensive soil moisture records to estimate "inverse-calibrated Soil Hydraulic Properties (SHPs)" using a multi-processing technique via high-performance computing clusters. Within this objective, a mass conservative numerical model was developed to solve the one-dimensional Richards Equation incorporating two different soil hydraulic models: the well-known van Genuchten Mualem (VGM) model and the relatively new Fredlund-Xing-Wang (FXW). A multiprocessing version of the Differential Evolution Algorithm (DEA) optimization technique was used for inverse calibration of the soil hydraulic parameters. For FXW, calibration statistics were calculated as means of the KGE' (0.89 f 0.1 and 0.83 f 0.23), R (0.89 f 0.1 and 0.85 f 0.21) and ubRMSE (0.017 f 0.01 and 0.015 f 0.02) for the depths 50 and 100 cm, respectively. For VGM, calibration statistics were found as means of the KGE' (0.87 f 0.11 and 0.78 f 0.22), R (0.90 f 0.08 and 0.86 f 0.17) and ubRMSE (0.019 f 0.01 and 0.017 f 0.01) for the same depths, respectively. The employed methodology had highly promising statistical performance for both FXW and VGM to derive SHPs. A comprehensive validation methodology was used to evaluate the reliability of derived SHPs. Correlation analysis showed that derived SHPs strongly correlated with the soil properties and environmental variables. Further, as a validation procedure, initial investigations were also conducted to explore the spatial transferability of the parameters. Despite the use of basic k-means clustering, the resulting soil hydraulic datasets showed statistical similarity or even improvement to hyper-resolution maps used in the literature. While the simulation model of the methodology has certain assumptions and limitations, this study proves that the ISMN database can be used to derive soil hydraulic properties and transfer these parameters to locations other than the calibration points. This study shows that FXW is a promising hydraulic model for the determination of soil moisture at root zone within the complete moisture range. The methodology can also be readily extended to other established soil moisture monitoring networks and potentially extended versions of "inverse-calibrated SHPs" and trained pedotransfer functions are considered to be valuable tools to estimate soil moisture profiles at the root zone.