Civil Engineering / İnşaat Mühendisliği

Permanent URI for this collectionhttps://hdl.handle.net/11147/13

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1995 - 199912000 - 20102

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Author: search.filters.author.Tanji, Kenneth K.Department: search.filters.department.İzmir Institute of Technology. Civil Engineering

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Now showing 1 - 3 of 3
  • Article
    Citation - WoS: 4
    Citation - Scopus: 4
    Two-Dimensional Finite Elements Model for Boron Management in Agroforestry Sites
    (Springer Verlag, 2010) Tayfur, Gökmen; Tanji, Kenneth K.; Baba, Alper
    Agroforesty systems, which are recommended as a management option to lower the shallow groundwater level and to reuse saline subsurface drainage waters from the tile-drained croplands in the drainage-impacted areas of Jan Joaquin Valley of California, have resulted in excessive boron buildup in the soil root zone. To assess the efficacy of the long-term impacts of soil boron buildup in agroforesty systems, a mathematical model was developed to simulate non-conservative boron transport. The developed dynamic two-dimensional finite element model simulates water flow and boron transport in saturated-unsaturated soil system, including boron sorption and boron uptake by root-water extraction processes. The simulation of two different observed field data sets by the developed model is satisfactory, with mean absolute error of 1.5 mg/L and relative error of 6.5%. Application of the model to three different soils shows that boron adsorption is higher in silt loam soil than that in sandy loam and clay loam soils. This result agrees with the laboratory experimental observations. The results of the sensitivity analysis indicate that boron uptake by root-water extraction process influences the boron concentration distribution along the root zone. Also, absorption coefficient and maximum adsorptive capacity of a soil for boron are found to be sensitive parameters. © 2009 Springer Science+Business Media B.V.
  • Article
    Citation - WoS: 14
    Citation - Scopus: 14
    Two-Dimensional Finite Elements Model for Selenium Transport in Saturated and Unsaturated Zones
    (Springer Verlag, 2010) Tayfur, Gökmen; Tanji, Kenneth K.; Baba, Alper
    A two-dimensional finite element model was developed to simulate species of selenium transport in two dimensions in both saturated and unsaturated soil zones. The model considers water, selenate, selenite, and selenomethionine uptake by plants. It also considers adsorption and desorption, oxidation and reduction, volatilization, and chemical and biological transformations of selenate, selenite, and selenomethionine. In addition to simulating water flow, selenate, selenite, and selenomethionine transport, the model also simulates organic and gaseous selenium transport. The developed model was applied to simulate two different observed field data. The simulation of the observed data was satisfactory, with mean absolute error of 48.5 μg/l and mean relative error of 8.9%. © 2009 Springer
  • Article
    Citation - WoS: 12
    Citation - Scopus: 13
    Modeling Deficit Irrigation in Alfalfa Production
    (American Society of Civil Engineers (ASCE), 1995) Tayfur, Gökmen; Tanji, Kenneth K.; House, Brett; Robinson, Frank; Teuber, Larry; Kruse, Gordon
    A conceptual agronomic model EPIC was extended to consider the effects of salinity in alfalfa production under optimal and water stress irrigation conditions. The extended model was calibrated and validated with observed lysimeter data. The model parameters that affected alfalfa yield and soil salinity the most were wilting point, field capacity, hydraulic conductivity, nitrate concentration, biomass energy ratio, seeding rate, average soil salinity EC e at which crop yield is reduced by 50% ( EC50 ), and initial soil gypsum concentration. The calibrated and validated model was then applied to an alfalfa deficit irrigation study. The four irrigation treatments included optimum check, minimum stress, short stress, and long stress, each of which produced differential alfalfa yields. The purpose of summer deficit irrigation was to ascertain how much agricultural water at what cost could be made available for urban water uses during water shortfalls. The results of model simulation were found to be satisfactory under all irrigation treatments though the model slightly overestimated the yields and underestimated the soil EC e at the end of short and long stress treatments. An economic component is included to determine the appropriate compensation for farmers undergoing a range of deficit irrigations.