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Downscaling of the Land Surface Temperature Data Obtained at four Different Dates in a Year Using the GWR Model: A Case Study in Antakya, Turkey
(Springer, 2023) Irvem, Ahmet; Ozbuldu, Mustafa
Land surface temperature (LST) is a major factor that affects many biophysical processes in the land-atmosphere relationship. This factor is obtained from satellite images having different temporal and spatial resolutions. This study applied the geographically weighted regression (GWR) model for four different dates representing each season a year to improve the LST images obtained in coarse resolution. In this study, MODIS LST images that are available having fine temporal but coarse spatial resolution were modeled using NDBI and NDVI indices, and their spatial resolution is improved. In addition, LANDSAT 8 images were used as reference images to evaluate the accuracy of the images obtained from the models. Results of the GWR model have been evaluated by comparing it statistically with TsHARP and DisTradother commonly used methods. As a result of the comparison by using the average of four dates outputs, the GWR model (R-2 = 0.73, RMSE = 0.78) was more successful than the TsHARP (R-2 = 0.56, RMSE = 1.00) and DisTrad (R-2 = 0.49, RMSE = 1.09) methods. The most successful downscaling performance in the GWR model was obtained in the spring season (RSR = 0.48). According to these findings, the GWR model can be used for downscaling LST images in urban areas. However, before applying this algorithm to scenarios outside of urban areas, it is recommended to use the required parameters and optimize their combinations.
Estimating spatial distribution of soil loss over Seyhan River Basin in Turkey
(Elsevier Science Bv, 2007) Irvem, Ahmet; Topaloglu, Fatih; Uygur, Veli
The purpose of this study was to investigate the spatial distribution of annual soil loss; soil loss in Seyhan River Basin using USLE model. A geographic information system (GIS) was used to generate maps of the USLE factors which are rainfall erosivity (R), soil erodibitity (K), slope length and steepness (LS), cover (C) and conservation practices (P) factors. By integrating these maps in GIS, spatial distribution of soil loss over the Seyhan River Basin was obtained. Annual average soil loss for the Seyhan River Basin was 16.38 t ha(-1) y(-1). Annual soil loss more than 200 t ha(-1) y(-1) in pixel level was in the southern region, white the northern region showed the lower annual values. These results are verified by comparing sediment yield measurements in the basin. An area about 198.25 km(2) (0.96%) experiences extremely severe erosion risk, which needs suitable conservation measures to be adopted on a priority basis. The spatial distribution of erosion risk classes estimated 61.03% very low, 8.76% low, 23.52% moderate, 4.03% severe and 1.70% very severe. Thus, the USLE model was used in a GIS environment to identify regions susceptible to water erosion and needing immediate soil conservation planning and application in the Seyhan River Basin in Turkey. (c) 2006 Elsevier B.V. All rights reserved.
Evaluating the impact of land use uncertainty on the simulated streamflow and sediment yield of the Seyhan River basin using the SWAT model
(Tubitak Scientific & Technological Research Council Turkey, 2014) El-Sadek, Ashraf; Irvem, Ahmet
As a result of the increased availability of spatial information in watershed modeling, several easy to use and widely accessible spatial datasets have been developed. Yet, it is not easy to decide which source of data is better and how data from different sources affect model outcomes. In this study, the results of simulating the stream flow and sediment yield from the Seyhan River basin in Turkey using 3 different types of land cover datasets through the soil and water assessment tool (SWAT) model are discussed and compared to the observed data. The 3 land cover datasets used include the coordination of information on the environment dataset (CORINE; CLC2006), the global land cover characterization (GLCC) dataset, and the GlobCover dataset. Streamflow and sediment calibration was done at monthly intervals for the period of 2001-2007 at gauge number 1818 (30 km upstream of the Catalan dam). The model simulation of monthly streamflow resulted in good Nash-Sutcliffe efficiency (NSE) values of 0.73, 0.71, and 0.68 for the GLCC, GlobCover, and CORINE datasets, respectively, for the calibration period. Furthermore, the model simulated the monthly sediment yield with satisfactory NSE values of 0.48, 0.51, and 0.46 for the GLCC, GlobCover, and CORINE land cover datasets, respectively. The results suggest that the sensitivity of the SWAT model to the land cover datasets with different spatial resolutions and from different time periods was very low in the monthly streamflow and sediment simulations from the Seyhan River basin. The study concluded that these datasets can be used successfully in the prediction of streamflow and sediment yield.
EVALUATION OF FLOOD SIMULATION FOR ZEYZOUN DAM-BREAK IN SYRIA USING HEC-RAS MODEL
(Parlar Scientific Publications (P S P), 2020) Irvem, Ahmet; Ozbuldu, Mustafa
Dams are the storage structure constructed across the river to store water in the upstream and release it to downstream as and when the demand arises. It is necessary to carry out dam-break analysis to study the behavior of the flood wave generated from the dam-break. It is necessary to prepare the inundation maps as a part of the emergency action plan to evacuate the population during the flood event. In this study, a simulation of the flood event that resulted in the Zeyzoun dam-break in Syria has been conducted using the HEC-RAS software. The simulation results were evaluated by considering flood risk areas, flood lag time, which is an important information for early warnings, and performance of the HEC-RAS model. Simulations were performed using different inlet hydrograph values until accurate results obtained, based on observed streamflow data. When, 286 m(3)/s inlet flow-rate is used as an input, a relatively better simulation outflow 109 m(3)/s is obtained in comparison with an observed flow of 143 m(3)/s. Flood lag time, which is an important information for early warnings, was found to be 50 hours. These observations from the simulation model gave relatively correct results. Also, this study indicates that flood simulation and peak discharge forecasting can be easily performed using the HEC-RAS model.
Evaluation of flood simulation for zeyzoun dam-break in Syria using hec-ras model
(Parlar Scientific Publications, 2020) Irvem, Ahmet; Ozbuldu, Mustafa
Dams are the storage structure constructed across the river to store water in the upstream and release it to downstream as and when the demand arises. It is necessary to carry out dam-break analysis to study the behavior of the flood wave generated from the dam-break. It is necessary to prepare the inundation maps as a part of the emergency action plan to evacuate the population during the flood event. In this study, a simulation of the flood event that resulted in the Zeyzoun dam-break in Syria has been conducted using the HEC-RAS software. The simulation results were evaluated by considering flood risk areas, flood lag time, which is an important information for early warnings, and performance of the HEC-RAS model. Simulations were performed using different inlet hydrograph values until accurate results obtained, based on observed streamflow data. When, 286 m3/s inlet flow-rate is used as an input, a relatively better simulation outflow 109 m3/s is obtained in comparison with an observed flow of 143 m3/s. Flood lag time, which is an important information for early warnings, was found to be 50 hours. These observations from the simulation model gave relatively correct results. Also, this study indicates that flood simulation and peak discharge forecasting can be easily performed using the HEC-RAS model. © 2020 Parlar Scientific Publications. All rights reserved.
Evaluation of Satellite and Reanalysis Precipitation Products Using GIS for All Basins in Turkey
(Hindawi Ltd, 2019) Irvem, Ahmet; Ozbuldu, Mustafa
Use of the satellite and reanalysis precipitation products, as supplementary data sources, are steadily rising for hydrometeorological applications, especially in data-sparse areas. However, the accuracy of these data sets is often lacking, especially in Turkey. This study evaluates the accuracy of satellite precipitation product (TRMM 3B42V7) and reanalysis precipitation product (NCEP-CFSR) against rain gauge observations for the 1998-2010 periods. Average annual precipitation for the 25 basins in Turkey was calculated using rain gauge precipitation data from 225 stations. The inverse distance weighting (IDW) method was used to calculate areal precipitation for each basin using GIS. According to the results of statistical analysis, the coefficient of determination for the TRMM product gave satisfactory results (R-2 > 0.88). However,R(2)for the CFSR data set ranges from 0.35 for the Eastern Black Sea basin to 0.93 for the West Mediterranean basin. RMSE was calculated to be 95.679 mm and 128.097 mm for the TRMM and CFSR data, respectively. The NSE results of TRMM data showed very good performance for 6 basins, while the PBias value showed very good performance for 7 basins. The NSE results of CFSR data showed very good performance for 3 basins, while the PBias value showed very good performance for 6 basins.
Evaluation of the performance of CFSR reanalysis data set for estimating reference evapotranspiration (ET0) in Turkey
(Firenze Univ Press, 2022) Irvem, Ahmet; Ozbuldu, Mustafa
Evapotranspiration is a key process and a necessary parameter for hydrological, meteorological, and agricultural studies. However, the calculation of actual evapotranspiration is very challenging and costly. Therefore, reference evapotranspiration (ET0) calculated using meteorological data is generally preferred over actual evapotranspiration. However, it is challenging to get complete and accurate data from meteorology stations in rural and mountainous regions. This study examined the suitability of the Climate Forecast System Reanalysis (CFSR) reanalysis data set as an alternative to meteorological observation stations to compute seasonal reference evapotranspiration for seven different climatic regions of Turkey. The ET0 calculations using the CFSR reanalysis dataset for 1987-2017 were compared to data at 259 weather stations observed in Turkey. As a result of statistical evaluations, it has been determined that the most successful predicted season is winter (C' = 0.64-0.89, SPAEF= 0.63-0.81). The most successful estimations for this season were obtained from coastal areas with low elevations. The weakest estimations were obtained for the summer season (C' = 0.52-0.85, SPAEF= 0.59-0.77). These results show that the ET0 estimation ability of the CFSR reanalysis dataset is satisfactory for the study area. In addition, it has been observed that CFSR tends to overestimate the observation data, especially in the southern and western regions. These findings indicate that the results of the ET0 calculation using the CFSR reanalysis data set are relatively successful for the study area. However, the data should be evaluated with observation data before being used, especially in the summer models.
Identification of flood risk area in the Orontes river basin, Turkey, using multi-criteria decision analyses
(Wfl Publ, 2012) Irvem, Ahmet; Topaloglu, Fatih
The objective of this study was to evaluate flood risk area for the Orontes river basin in Turkey, using the Multi-Criteria Decision Analysis (MCDA) within the Geographic Information Systems. Flood risk areas were evaluated using rainfall, slope, elevations, size of sub-watersheds and soil types. These factors were chosen as the most influential factors for generating the flood risk map. MCDA was performed by adding the weighted flood rankings of all the causative factors, according to their relative importance to each other and to their expected importance in causing floods. ILWIS, GIS software was used for spatial analyses and MCDA. Estimated risk map for the Orontes river basin obtained by adding the weighted flood rankings of all factors classified in five categories. producing risk levels of non-flood, low, moderate, high, and very high. It was found that non-flood accounted for 1252.2 km(2) (15.7%) of the total. low for 1032.3 km(2) (13%), moderate for 1596 km(2) (20%), high for 2607.4 km(2) (32.8%) and very high flood risk area for 1471.4 km(2) (18.5%). The Ministry of Agriculture and Rural Affairs of Turkey mapped the flood area for the Orontes river basin from field measurement and their observations were compared with a generated flood risk map. The comparison showed satisfactory results because observed flood area was determined to be in very high flood risk region in the flood risk map. Thus, flood risk area identification using MCDA is possibly suitable for flood planning and management.
Mapping of total nitrogen, available phosphorous and potassium in Amik Plain, Turkey
(Springer, 2010) Uygur, Veli; Irvem, Ahmet; Karanlik, Sema; Akis, Rifat
Soil nitrogen, phosphorous, and potassium concentrations accurately revealed spatial distribution maps and site-specific management-prone areas through inverse distance weighting (IDW) method in the Amik Plain, Turkey. Spatial mapping of soil nitrogen, phosphorous, and potassium is a very severe need to develop an economically and environmentally sound soil management plans. The objectives of this study were (a) to map spatial variability of total N, available P, and exchangeable-K content of Amik Plain's soils and (b) to locate problematic areas requiring site specific management strategies for the nutrient elements. Spatial analyses of Kjeldhal-N, Olsen-P, and exchangeable-K concentrations of the soils were performed by the IDW method. Mean N content for surface soils (0-20 cm) was 1.38 g kg(-1), available P was 28.19 kg ha(-1) and exchangeable-K was 690 kg ha(-1) with the differences between maximum and minimum being 7.63 g N kg(-1), 242 kg P ha(-1), and 2,082 kg K ha(-1). For the surface soil, site-specific management-prone areas of Kjeldahl-N, Olsen-P, and exchangeable-K for low and high + very high'' classes were found to be 20.1-17.8%, 24.7-10.0%, and 4.1-39.6%, respectively. Consequently, lands with excessive nutrient elements require preventive-leaching practices, whereas nutrient-poor areas need fertilizer applications in favor of increasing plant production.
PIXEL SIZE EFFECTS ON DAM WATER STORAGE CAPACITY ESTIMATION USING GIS: CASE STUDY OF BUYUK KARACAY DAM, TURKEY
(Parlar Scientific Publications (P S P), 2020) Irvem, Ahmet
There are both, technical and operational. constraints to determine the suitable location and water storage capacity of a dam. as it requires extensive fieldwork by qualified technicians, followed by lengthy data analyses. To overcome these constraints, water storage capacity can be pre-estimated using Digital Elevation Model (DEM) which was generated from a digitized topographic map for any basin. In this study. the Buyuk Karacay Dam. located in Hatay province of Turkey was chosen for the case study. The water storage volume for the Buyuk Karacay Dam was estimated, using the DEM in GIS environment. Storage volume calculation procedures according to crest elevation of created virtual dam and topography were described. Maps of the stream network, stream order, and flooded areas were generated, using DEM in Ilwis 3.6 software. DEM having 10-, 20-, 30-, 40- and 50-meter pixel sizes, were used to calculate storage volume based on dam crest elevation which was 347 meters from sea level. The estimated volumes have been compared to determine pixel size effects on volume prediction, with results of the survey method which have been conducted after construction of Buyuk Karacay dam. Those results showed that 10-meter pixel size results in the best volume estimation. According to ten-meter pixel size. dam reservoir storage capacity was estimated 59.38 hm(3). This estimation is very close to the result of the survey method, which was 57.25 hm(3).
Pixel size effects on dam water storage capacity estimation using GIS: Case study of buyuk karacay dam, Turkey
(Parlar Scientific Publications, 2020) Irvem, Ahmet
There are both, technical and operational, constraints to determine the suitable location and water storage capacity of a dam, as it requires extensive fieldwork by qualified technicians, followed by lengthy data analyses. To overcome these constraints, water storage capacity can be pre-estimated using Digital Elevation Model (DEM) which was generated from a digitized topographic map for any basin. In this study, the Buyuk Karacay Dam, located in Hatay province of Turkey was chosen for the case study. The water storage volume for the Buyuk Karacay Dam was estimated, using the DEM in GIS environment. Storage volume calculation procedures according to crest elevation of created virtual dam and topography were described. Maps of the stream network, stream order, and flooded areas were generated, using DEM in Ilwis 3.6 software. DEM having 10-, 20-, 30-, 40- and 50-meter pixel sizes, were used to calculate storage volume based on dam crest elevation which was 347 meters from sea level. The estimated volumes have been compared to determine pixel size effects on volume prediction, with results of the survey method which have been conducted after construction of Buyuk Karacay dam. Those results showed that 10-meter pixel size results in the best volume estimation. According to ten-meter pixel size, dam reservoir storage capacity was estimated 59.38 hm3. This estimation is very close to the result of the survey method, which was 57.25 hm3. © by PSP.
Potential of kernel and tree-based machine-learning models for estimating missing data of rainfall
(Hong Kong Polytechnic Univ, Dept Civil & Structural Eng, 2020) Sattari, Mohammad Taghi; Falsafian, Kambiz; Irvem, Ahmet; Shahab, S.; Qasem, Sultan Noman
In this study, two kernel-based models were used which include Support Vector Regression (SVR) and Gaussian Process Regression (GPR) and were compared with two tree-based models that are M5 and Random Forest (RF) for estimating missing monthly precipitation data in Antakya, Dortyol, Iskenderun and Samandag stations, which are the important precipitation stations in the Eastern Mediterranean region, Turkey. For this purpose, firstly 10% random precipitation data were assumed as missing data for the period 1980-2019. Secondly, the missing data in each station was estimated with the data of other stations within the framework of four data combinations scenarios. In Kernel-based SVR and GPR methods, the RBF kernel gave suitable results for the selected study area. While SVR and RF methods gave very close estimation results, the SVR method gave relatively better results than the other methods especially in error minimizing aspects. Gaussian function based GPR model generally tries to estimate missing data closer to means. This is the main disadvantage of the GPR model and therefore it is unsuccessful in the estimation process. Finally, the results showed that the algorithms based on machine learning are successful in estimating the missing precipitation data.
Re-evaluation of trends in annual streamflows of Turkish rivers for the period 1968-2007
(2012) Topalo?lu, Fatih; Irvem, Ahmet; Özfidaner, Mete
The Mann-Kendall rank correlation test was performed to detect trends in this study. The research investigated 3 annual stream-flow variables including annual instantaneous minimum, mean and instantaneous maximum streamflows for a network of 57 Turkish streamflow gauging stations in 25 basins of Turkey, during 1968-2007. The application of trend detection technique to 3 stream-flow variables has resulted in the identification of significant decreasing trends at the 0.05 level, appearing mostly in the basins in western and partly in southeastern Turkey, whereas almost no.evidence of significant change was experienced with a general downward direction in the rest of the country. Of the 25 basins, however, only basins with the numbers of 12 and 22 exhibited significant increasing trend for one station each. The number of stations showing a decreasing trend is more than 9-fold that of stations with an upward trend whereas the significant downtrend exceeded the uptrends 49-fold. Besides, almost 2/3 of the decreasing trends (144 times over 159) were found to be statistically significant while approximately 13% of the increasing trends (15 times) exhibited significant trend. © by PSP.
RE-EVALUATION OF TRENDS IN ANNUAL STREAMFLOWS OF TURKISH RIVERS FOR THE PERIOD 1968-2007
(Parlar Scientific Publications (P S P), 2012) Topaloglu, Fatih; Irvem, Ahmet; Ozfidaner, Mete
The Mann-Kendall rank correlation test was performed to detect trends in this study. The research investigated 3 annual stream-flow variables including annual instantaneous minimum, mean and instantaneous maximum streamflows for a network of 57 Turkish streamflow gauging stations in 25 basins of Turkey, during 1968-2007. The application of trend detection technique to 3 stream-flow variables has resulted in the identification of significant decreasing trends at the 0.05 level, appearing mostly in the basins in western and partly in southeastern Turkey, whereas almost no evidence of significant change was experienced with a general downward direction in the rest of the country. Of the 25 basins, however, only basins with the numbers of 12 and 22 exhibited significant increasing trend for one station each. The number of stations showing a decreasing trend is more than 9-fold that of stations with an upward trend whereas the significant downtrend exceeded the uptrends 49-fold. Besides, almost 2/3 of the decreasing trends (144 times over 159) were found to be statistically significant while approximately 13% of the increasing trends (15 times) exhibited significant trend.
REGIONAL DROUGHT ANALYSIS FOR THE EASTERN MEDITERRANEAN REGION OF TURKEY USING RUN AND SPI METHOD
(Parlar Scientific Publications (P S P), 2020) Saglamoglu, Ahmet; Irvem, Ahmet
The identification, monitoring and characterization of droughts are matters of great importance in water resources planning and management. In this study, drought characteristics, using monthly precipitation data from 22 meteorological stations in the years between 1960-2015, are investigated in a regional -scale. The run and SPI methods supporting the ReDIM software, were applied to three- and 12 months' time-scales for the East Mediterranean Region of Turkey. Outputs of some drought characteristics were mapped using ILWIS software. Results of the SPI regional analysis, based on a three-months' time-scale showed that a minimum SPI (-1.60) was seen in February 1991, while a maximum SPI (-2.79) was seen in November 1975. Based on a 12-months' time-scale, a minimum SPI (-1.71) was seen between January and February 1983. A maximum SPI (-2.76) was reached between June 1973 and January 1974. According to the results of the run method, the longest drought durations were found to be 12 years for the Anamur station, nine years for Kilis and eight years for Adana. The maximum drought intensity was 588 mm/year for Antalya station. A maximum water deficit was calculated to be 1744 mm for Anamur. Generally, the longest drought durations, drought intensity and cumulated water deficits decreased throughout the north of the region. Results show that the collected date in relation with regional droughts identified with SPI provide more details of drought durations and magnitudes.
Regional drought analysis for the eastern mediterranean region of Turkey using run and spi method
(Parlar Scientific Publications, 2020) Saglamoglu, Ahmet; Irvem, Ahmet
The identification, monitoring and characterization of droughts are matters of great importance in water resources planning and management. In this study, drought characteristics, using monthly precipitation data from 22 meteorological stations in the years between 1960-2015, are investigated in a regional-scale. The run and SPI methods supporting the ReDIM software, were applied to three- and 12-months' time-scales for the East Mediterranean Region of Turkey. Outputs of some drought characteristics were mapped using ILWIS software. Results of the SPI regional analysis, based on a three-months' time-scale showed that a minimum SPI (-1.60) was seen in February 1991, while a maximum SPI (-2.79) was seen in November 1975. Based on a 12-months` time-scale, a minimum SPI (-1.71) was seen between January and February 1983. A maximum SPI (-2.76) was reached between June 1973 and January 1974. According to the results of the run method, the longest drought durations were found to be 12 years for the Anamur station, nine years for Kilis and eight years for Adana. The maximum drought intensity was 588 mm/year for Antakya station. A maximum water deficit was calculated to be 1744 mm for Anamur. Generally, the longest drought durations, drought intensity and cumulated water deficits decreased throughout the north of the region. Results show that the collected date in relation with regional droughts identified with SPI provide more details of drought durations and magnitudes. © 2020 Parlar Scientific Publications. All rights reserved.
Trends in Turkish monthly mean streamflow
(Wfl Publ, 2012) Irvem, Ahmet; Topaloglu, Fatih; Ozfidaner, Mete
The research explored trends in monthly mean streamflow variables for a network of 57 Turkish streamflow gauging stations in 25 basins of Turkey. The procedure employs the Mann-Kendall rank correlation test to detect trends. The application of Mann-Kendall test resulted in the identification of significant decreasing trends at the 0.05 level appearing mostly in the basins in western Turkey whereas almost no evidence of significant change was experienced with a general downward direction in the rest of the country. Of the 57 stations, however, only 406, 712, 1226, 1402, 1517 and 2233 exhibited significant increasing trend over Turkey. The number of stations showing a decreasing trend is more than sevenfolds the number of stations with an upward trend, whereas the significant downtrend exceeded the uptrends by twentyfolds. Besides, more than half of the decreasing trends were found statistically significant while approximately 21% of the increasing trends exhibited significant trend. Hydrologically, these results indicate that Turkey is generally getting drier.

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