Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Simulation of Water Resources of Tahtalı-Seferihisar Sub-Basin Based on Weap Model(Izmir Institute of Technology, 2021) Karahan, Sait Mutlu; Elçi, ŞebnemWater is a vital resource for humanity and nature, and the lack of water affects life in all areas. Today, problems such as the inability to protect the status of existing water resources and excessive water withdrawal cause the amount of water to decrease day by day. In addition, conditions such as urbanization and industrialization and the resulting population increase, deterioration of water quality due to chemicals used in agricultural activities, and climate change affect the availability of water resources negatively. In this study, a basin-based water management study was carried out by applying the "Integrated Water Resources Management" approach to the Tahtalı-Seferihisar Sub-Basin located in Turkey, where it is expected to experience water stress in the future. The hydrological (precipitation, flow, evaporation) data of the water resources that are important for the basin and İzmir (Tahtalı, Seferihisar, Ürkmez, and Kavakdere Dams) were used to predict the availability of water resources in the future using the WEAP (Water Evaluation and Planning System) program, and several possible scenarios for water demands/supplies were analyzed. Under these situations, the water budget balances expected to occur 2050 have been estimated. Basically, seven different scenarios were created to transfer possible future possibilities to the program: Reference Scenario, Best Case Scenario, Worst Case Scenario, Report Consumption Scenario, Return Flow Scenario, Population Projection Scenario and Various Forecast Scenario. The water balances that can be obtained under different conditions in each scenario were calculated and compared with each other.Master Thesis Numerical Modeling of the Artificial Destratification of the Thermally Stratified Water Column by Air Diffusers(01. Izmir Institute of Technology, 2021) Bahadıroğlu, Nisa; Elçi, ŞebnemReservoirs have essential roles in water management due to the large areas of use. In a reservoir, the structure of the temperature profile in the vertical water column mainly controls the vertical distribution of heat, dissolved substances, and nutrients. Thermal stratification in the water column can lead to an anoxic and poor quality water source. Artificial destratification has been widely used to improve water quality in thermally stratified water sources. This study focuses on the numerical modeling of artificial destratification of thermally stratified water columns by air diffusers to improve the water quality of reservoirs. Firstly, destratification experiments were performed to verify the numerical models. In the experiments, the effects of air diffuser hole diameter, air flow rate, and the number and configuration of holes on the diffuser on destratification time and efficiency were observed. The second part of the study comprised the numerical modeling of hydrodynamics during the destratification of thermally stratified water columns by air diffusers. ANSYS Fluent software is utilized for the simulation of the hydrodynamic processes. Model options for multiphase flows, boundary conditions, and turbulence; and their comparison with experimental studies are discussed. The Eulerian multiphase model and k-ω turbulence model were found to be suitable for this study. In the final part, the numerical model was verified with the experiments. Based on the error analysis of comparisons of the model and observations, the best configuration of air diffuser is proposed, and the numerical model was found to be successful in simulating the destratification of thermally stratified water columns by air diffuser.Master Thesis Design of Coanda Intakes for Optimum Sediment Release Efficiencies and Water Capture Performances(Izmir Institute of Technology, 2020) Hazar, Oğuz; Tayfur, Gökmen; Elçi, ŞebnemBottom type water intake structures are frequently preferred in the case of flows containing high levels of sediment in case where it is not possible to construct settling pool or if their construction costs are high. Coanda and Tyrolean type water intake structures are the most commonly used bottom type intake structures. It has been observed in a limited number of studies that Coanda type water intakes are superior to the Tyrolean type water intakes both in terms of withdrawing the design amount of flow and excluding the sediment as much as possible. However, the biggest obstacle to the widespread usage of Coanda type water intake is their complex design and difficulties of the analysis. It has been observed that there are no formula or numerical studies that calculate the water Capture Performance (WCP) and Sediment Release Efficiency (SRE) of the Coanda screens. In order to overcome this gap in the literature, six different Coanda screens have been tested for both WCP and SRE using various incoming flows and sediment compositions. The data obtained as a result of the experimental studies were analyzed using statistical analysis method and two different equations were obtained that enable to find the WCP and SRE. In a situation where the incoming flow conditions and screen parameters are known, someone can gain a preliminary knowledge about the screen performance by using these equations. As a result of this study, adding new data to the literature and eliminating the mentioned lack in the literature was aimed.Master Thesis Effects of Oxygenation in Stratified Reservoirs on Concetrations of Manganese and Iron in Bottom Sediments(Izmir Institute of Technology, 2019) Vural Aydın, Buse; Elçi, Şebnem; Ökten, Hatice EserIron and manganese accumulation in drinking water reservoirs is a challenging issue and should be controlled in order to prevent their adverse effects on human health. Accumulation of these elements not only clogs pipeline systems but also causes stains on fixtures and laundry. In addition, high concentrations of iron and manganese may lead to various health problems when ingested. This study focuses on the release mechanism of iron and manganese from sediments to water column and investigates methods to prevent this release. Effects of lack of hypolimnetic aeration, acid-base condition and thermal stratification on iron and manganese concentrations at water column were investigated through laboratory experiments. Experiments showed that total iron (Fe) and ferrous iron (Fe2+) concentrations in the water column decreased gradually following aeration in hypoxia conditions. A similar behavior was also observed for manganese concentrations. However, the concentration of dissolved manganese (Mn) in alkaline water condition is observed to be less than the aerated water case. This is an indication that iron and manganese react differently under different acidity of water in consideration.Master Thesis Modification of a Computational Fluid Dynamics Model (ansys-Fluent) for the Purpose of River Flow and Sediment Transport Modeling(Izmir Institute of Technology, 2015) Ekmekçi, Hüseyin Burak; Elçi, ŞebnemPrecise estimation of the sediment transport and settling velocity of particle in turbulent flows is required for many engineering applications including modeling of the transport of suspended sediments and the transport of particle pollutants. This study presents an approach for modification of an existing CFD Model for sediment transport in turbulent flow based on field measurements. In the first part, synchronized 3-D velocity and temperature time series were monitored at Büyük Menderes River in Turkey where the data were utilized to characterize the turbulence characteristics and model particle – fluid interaction. Sieve and hydrometer analysis were obtained from earlier studies to understand and modify sediment transport under different conditions via ANSYS Fluent programme. The second part of the study involved numerical modeling of hydrodynamics via 3D CFD model in the selected portion of a river body through use of field measurements conducted at the study site. The k-ω turbulence model found to be the best suited when such flow around a structure as piers or flow through a water intake is considered. Effect of particle size, concentration and modeling approach for particle motion are also investigated and Rossin Rammler Logarithmic Distribution and multiphase modeling approach was the most appropriate methods. This study involved development of an approach to modify drag force on sediment particles using turbulence characteristics in the Fluent solver as well.Master Thesis Estimation of Suspendent Sediment Concentration Using Acoustic Methods(Izmir Institute of Technology, 2009) Aydın, Ramazan; Elçi, ŞebnemAcoustic Doppler current meters (ADCP, ADP, and ADV) can provide information about the suspended sediment concentration (SSC) in the water; although, they are designed for flow velocity measurements. Contrary to conventional samplers, those are labor intensive for measuring SSC, when an acoustic instrument is calibrated for a water system; no additional sensor is needed to measure SSC, enabling the researchers to measure velocity and concentration simultaneously which is required for most sediment transport studies. Recently, the acoustic instruments are investigated in different studies where signal to noise ratio (SNR) and SSC were related using different formulations. However, these studies were limited to single study site where neither the effect of particle size nor the effect of temperature was investigated. In the scope of this study, different parameters that affect the ADV.s performance prediction of SSC were investigated. In order to investigate the reliability of ADV in different environments, SSC measurements were made in different streams. Soil samples were collected from all measuring stations and particle size analysis was conducted. The multivariate data analysis was applied to the measurements to derive a relation formula between SNR and SSC. Multivariate analysis indicated that reported SSC values depended on at least three parameters; water temperature, mean diameter of the soil, and shape of the particle size distribution curve. Also, effect of high SSC conditions on ADV performance was investigated during and after rain events. Results indicated that ADV was not capable of measuring SSC when a limit concentration (SSC>400 mg/l) was exceeded.Master Thesis Investigation of Effects of Land Use Changes in Tahtalı River Basin on Water Quality(Izmir Institute of Technology, 2009) Selçuk, Pelin; Elçi, ŞebnemThe rapid increase of population, industrial growth and disorganized urbanization have put considerable stress on the available water sources, which are already scarce, not only by the increased usage but also by deterioration of the quality of available resources. Both statistical and GIS analyses were adopted in this study to examine the changes in water quality parameters associated with the changes in landuse within a major watershed in the city of Izmir, Turkey. In this study, the satellite images containing the periods prior and after filling of the main pool of the Tahtali reservoir, were analyzed and the effects of the land use changes on the water quality were investigated. For this purpose, the aerial photos of the basin taken in 1995 (October) composed of 130 sections having a scale of 1/5000 were obtained and these images were compared with images of the Ikonos satellite taken in 2005 (November) with a resolution of 1 meter. New residential buildings, greenhouses and industrial buildings were presented in separate layers to document changes in basin activities since 1995.Later on, changes in all 130 sections were merged and the thematic maps of the basin were obtained. This analysis utilized several GIS techniques including manual digitizing, remote sensing and use of existing digital base maps for the preparation of input data. The data analysis included transformation between map projections and data formats, editing of attributes and use of query functions, use of spatial overlaying and also both retrieval and classification.In order to investigate the effects of changes on the water quality, the water analysis values obtained from samples taken at 6 different reaches within the basin and at the main lake for the years of 1995-2005 were obtained. Seasonal Kendall and Mann Kendall tests were selected and applied to the water quality data to investigate which parameters increased/decreased and how these changes were related to the effects of urbanization and industrial development. This study also investigated and quantified soil erosion in the basin by the universal soil loss equation (USLE) for two different land use compositions and soil maps from two years: 1995 and 2005.Master Thesis Modeling of Hydrodynamics and Sedimentation in a Stratified Reservoir: Tahtalı Reservoir, Izmir(Izmir Institute of Technology, 2008) Çalışkan, Anıl; Elçi, ŞebnemThe main goal of this study was to investigate the hydrodynamics of a stratified reservoir for different flow and weather conditions through numerical modeling. This study also investigated the effects of selective withdrawal, climate change, and sediment deposition on hydrodynamics. A three-dimensional numerical model, Environmental Fluid Dynamics Code (EFDC) has been selected in the present study to model the hydrodynamics in the lake. The study site was selected as the main pool of Tahtali Reservoir providing 40% of the water used in the city of zmir (Population: 3.4 million by 2000). Applied numerical model was validated by monthly observations of water velocity and temperature profiles. Field measurements were performed from July 2006 to September 2007 in the lake and in two rivers (aal and Tahtali). The water velocity measurements in the lake were made using a 1.5-MHz acoustic Doppler current profiler. For water temperature and quality measurements, a hand-held water quality meter with a depth sensor were used for both lake and river measurements. Furthermore, a weather station was set up by the lake in order to collect accurate data for wind conditions in the study site.The numerical model predicted the observed velocity profiles and temperature time series satisfactorily. Possible reasons for discrepancies were investigated. Numerical model results indicated that water velocities were strongly dominated by the wind data and correct measurement of wind stress on the lake surface is necessary for accurate prediction of velocities in the water column. Withdrawal of the water at the bottom outlet was found to be the most effective choice encouraging the mixing of the water column. Possible climate change impacts modeled numerically indicated that the thermocline depths were lowered in the water column causing the deterioration of water quality. Sedimentation thickness was estimated via numerical modeling and the long term erosion rate was calculated by USLE method. Modeling the sedimentation zones provided valuable information on the capacity of the reservoir. The results of this study can be used to guide the further investigations in the lake including modeling of water quality for better management practices.Master Thesis Assessment of Impact of Reservoir's Contaminated Bottom Sediments on Surfacewater Quality by Sediment-Water Interaction Model(Izmir Institute of Technology, 2011) Şimşek, Sinem Elif; Elçi, ŞebnemIn this study, an approach for the assessment of the life-long impact of submersed contaminated bottom sediments in projected reservoirs on surface water quality is presented. A sediment-water interaction model designed to simulate contaminants in the sediments and in the overlying water column is developed and the impact of contaminated bottom sediments on water quality is investigated under different scenarios. One goal of this study is to investigate the contribution of contaminated soils underlying the reservoir compared to the contaminants transported by surface and groundwater influx. The proposed study predicts the long term impact of the selected site on water quality before the construction of the dam. The sediment-water interaction model developed in this study consists of three main layers: water column which can be specified as well mixed or stratified according to the temperature profile in the vertical column, a mixed sediment layer and a deep sediments layer. In the model, mass balance equations for contaminants are solved for the water column and the mixed sediment layer.This study further presents the projection of possible contamination in a reservoir based on the analysis of the soil samples collected from the reservoir bottom before the filling of the reservoir. Reverse modeling approach for the prediction of contaminant concentration in the water column originating from the bottom sediments is applied. Transfer of five heavy metals; Copper, Zinc, Chromium, Nickel, and Lead existing in bottom sediments of Çamlı Basin to the reservoir water is modeled.