Browsing by Author "KORKMAZ, SERDAR"

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A numerical groundwater flow model of Bursa Başköy aquifer
(Crc Press-balkema, 2016-01-01) Korkmaz, Serdar; Türkkan, Gökçen Eryılmaz; Erpicum, S; Dewals, B; Archambeau, P; Pirotton, M; KORKMAZ, SERDAR; Türkkan, Gökçen Eryılmaz; Uludağ Üniversitesi/Mühendislik Fakültesi/İnşaat Mühendisliği Bölümü; Erpicum, S; Dewals, B; Archambeau, P; Pirotton, M; 0000-0002-3393-1632; AAG-8542-2021; JHM-2140-2023
In this study, the aim is to determine the groundwater storage and distribution in the Baskoy aquifer inside the city of Bursa, Turkey. Preliminary studies were conducted in the GIS environment, and afterwards, groundwater flow simulations were performed in MODFLOW which uses finite differences method to solve groundwater flow equations. From point elevation data, a digital elevation model (DEM) was constructed. The subbasins and drainage network were delineated through hydrological analysis of the DEM. The data were transferred to MODFLOW interface and a grid with a cell size of 15 m x 15 m was generated. Hourly groundwater level measurements at 7 observation wells were obtained from State Hydraulic Works. The observation data were used for calibration of unknown parameters such as hydraulic conductivity and storage coefficient. Calibration process was expedited by using the Parameter Estimation (PEST) model. Transient simulations were performed in daily timesteps and according to the results, model output was dependent on the initial condition, hydraulic conductivity and storage coefficient. In most of the wells the general dynamics of groundwater were successfully predicted.
Determination of hydraulic conductivity using analytical and numerical methods applied to well and aquifer tests
(Türk İnşaat Mühendisleri Odası, 2015-01-01) Türkkan Eryılmaz, Gökçen; Korkmaz, Serdar; Türkkan Eryılmaz, Gökçen; KORKMAZ, SERDAR; Uludağ Üniversitesi/Mühendislik Fakültesi/İnşaat Mühendisliği Bölümü.; 0000-0002-3393-1632; AAG-8542-2021; ETJ-9151-2022
This study aims to determine the hydraulic conductivity of aquifers by analytical and numerical methods applied to water level data obtained from well and aquifer tests. Two wells 33 meters apart were drilled in an unconfined aquifer in Bursa Kucuk Sanayi region by Neojen Muhendislik. In one of the wells, a total of 18 slug tests were performed using different volumes before and after well development. Bouwer-Rice and Dagan methods were used as analytical methods and MODFLOW software, which solves groundwater flow problems using method of finite differences, was used for numerical modeling. In the other well, pumping tests were performed. Hantush-Bierschenk and Rorabaugh methods were applied to the data from step-drawdown tests and discharge-drawdown curves were obtained. In addition to these, recovery test and multirate test were performed to determine the hydraulic conductivity. In MODFLOW, simulations were made for various cases related to grid resolution and specific yield. It was observed that well development significantly contributes to well performance and the volume used in slug tests does not affect the results. In addition, different pumping tests modeled in MODFLOW yielded similar values of hydraulic conductivity.
Evaluation of pumping test data using analytical and numerical methods
(IAHR-int Assoc Hydro-environment Engineering Research, 2015-01-01) Korkmaz, Serdar; Eryılmaz, Gökçen Türkkan; Mynett, A; KORKMAZ, SERDAR; Eryılmaz, Gökçen Türkkan; Uludağ Üniversitesi/Mühendislik Fakültesi/İnşaat Mühendisliği Bölümü; Mynett, A; 0000-0002-3393-1632; AAG-8542-2021; ETJ-9151-2022
In this study, the well performance and near-well hydraulic conductivity are determined through analytical and numerical methods applied to water level data obtained from pumping tests. For this purpose, a well was drilled in an unconfined aquifer in Bursa Kucuk Sanayi region. In the well, several pumping tests, namely, step-drawdown test, recovery test and multirate pumping test were performed. Hantush-Bierschenk and Rorabaugh methods were applied to the data from step-drawdown tests and discharge-drawdown curves were obtained. On the other hand, recovery test and multirate test were performed to determine the hydraulic conductivity. MODFLOW software, which solves groundwater flow problems using method of finite differences, was used for numerical modeling. In MODFLOW, simulations of the pumping tests were made for various cases related to grid resolution and specific yield. The discharge-drawdown curve of MODFLOW was compared to those obtained from analytical solutions and a good correspondance was observed. In addition to this, multirate pumping test modeled in MODFLOW yielded a similar hydraulic conductivity as the analytical solution.
Steady-state analytical and numerical solutions of confined and unconfined flows in aquifers with discontinuous aquiclude
(Springer, 2019-03-01) Korkmaz, Serdar; KORKMAZ, SERDAR; Bursa Uludağ Üniversitesi/Mühendislik Fakültesi/İnşaat Mühendisliği Bölümü.; 0000-0002-3393-1632; AAG-8542-2021
Solution to combined confined and unconfined flows in multiple aquifer systems has been a challenging issue for groundwater flow modelers. In this study, steady-state solutions to four different problems are presented using analytical and numerical methods. For analytical solution, the concept of discharge potential is used. In this method, the governing equation becomes the same for both confined and unconfined flows. Moreover, discharge potential satisfies Laplace's Equation and hence the potential theory becomes applicable which makes easier to reach solutions to complex problems. The problem consisting of an aquifer with a discontinuous aquiclude was solved by using comprehensive potential which gives the solution in an entirely unconfined aquifer with equivalent boundary conditions. This facilitates the solutions to confined and unconfined regions above and below the aquiclude. For the numerical solutions, two different versions of MODFLOW, namely, MODFLOW-2005 and MODFLOW-NWT were used. Initially, two different resolution schemes were tested. One of the schemes yielded good predictions of heads for different types of input in which the flow direction and aquifer type varied.