Sharif Digital Repository

In many countries of the world, especially dry and semi-arid areas, coastal aquifers are used to provide fresh water. Many of these areas have also become urbanaized, which has made the need for freshwater more important. Seawater Intrusion (SWI) is the greatest limitation that influences the exploitation of groundwater in coastal aquifers, where with SWI, the amount of freshwater supply and other existing pumping wells are not used. The present study attempts to model SWI in karst and fractured coastal aquifers. For this purpose, two models with Discrete Fracture/Conduit Network approach in Fortran and also in COMSOL Multiphysics software have been developed to study the density-variable... 

The goal of this study is to explore the density-driven flow and study the effect of fracture as well as chemical processes and reactions on convective transport. Convective flow is used in connection with the density-driven flow where the flow is driven by density differences in the fluid, which can be affected by the ambient rocks. Several studies of density-driven flow in porous media have focused on the effect of heterogeneity on the mixing convection; however, they neglect the key processes of geochemical reactions in fractured porous media. This study aims to address this gap by investigating the combined effect of heterogeneity (as fractures) and the existing geochemical reactions on... 

Lake Urmia water level fell dramatically from 2006 to 2014. Since then the declining trend of water level has stopped but the lake has remained in a critical situation. Moreover, Lake Urmia became supersaturated with total salinity averaging more than 350 g/l. Salt precipitation and dissolved materials brought by inflowing rivers have formed a layer of sediment with low hydraulic conductivity on the lakebed. We conducted a series of numerical simulation scenarios to study the groundwater flow pattern in the vicinity of the hypersaline Lake Urmia using COMSOL Multiphysics®. In the first step, we performed the simulations in steady-state conditions. Secondly, we simulated the lake level fall... 

The goal of this research is to investigate the phenomenon of saltwater up-coning into pumping wells in fractured porous media. For this aim, two series of regular orthogonal fracture networks and different vertical and horizontal fracture apertures are simulated using an axisymmetric (2D vertical cross-section) model with a sharp interface approach. The effect of changing the pumping rate and the hydraulic conductivity has been examined to recognize other effective characteristics of the aquifer and pumping well on the saltwater up-coning. These simulations have been performed in COMSOL Multiphysics. The results indicate that the saltwater extent under the pumping well can be affected... 

Considering current problems in performance evaluation of the Cloud and its management policies and strategies, this thesis presents different approaches for simultaneous evaluation of the performance, dependability, and power consumption of Infrastructure-as-a-Service (IaaS) clouds. The proposed approaches use Stochastic Reward Nets (SRNs) and Stochastic Activity Networks (SANs) to model and evaluate performability and power consumption of cloud systems. In all of the proposed approaches, the cloud resource management system is power-aware. It means that idle Physical Machines (PMs), network equipment, and supporting subsystems are kept in powered-off or standby modes, as much as possible,... 

Quantitative estimation of baseflow is necessary for hydrological modeling of a watershed, ground-surface water interaction, water supply reliability, and vulnerability, especially during a dry period, and answering questions pertaining to the responses of human-based activities on natural ecosystems. Extensive research effort spanning more than 50 years provided collections of field, manual, and computer-based methods for baseflow separation study. In this study, a comprehensive review is carried out on the nine digital filters, six graphical methods, four tracer-mass-balance methods, fourteen recession analysis methods, and two frequency analysis methods. Sensitivity analyses of baseflow... 

Digital Elevation Models (DEM) is a crucial element of hydraulic models, including floods. Due to the lack of high-precision topographic data, including ground-based mapping hydraulic modeling is challenging. In recent years, remote sensing data, extensively used by many researchers in hydraulic modeling due to global coverage and free access. One of the most critical questions in hydraulic modeling is the efficiency of these DEMs in flood simulation. This research focused on using remote-sensing-based DEMs, such as SRTM-30m and 90m, ASTER-30m, and ALOS-12.5m DEMs, on the performance of the HEC-RAS-2D model in the Gorganrood river.The results showed that ALOS and SRTM-30m DEMs' accuracy and... 

Lake Urmia located in the NW of Iran, has lost 96 percent of its volume in 20 years and become a national crisis. During this shrinkage, the lake level has fallen by 8 m, and its concentration has increased up to 380 g/l. Regarding the vast area Lake Urmia basin is covered, the hydrological characteristics of the basin varies a lot, which affects the aquifers response to the seawater intrusion. In order to study the seawater intrusion in the lake’s aquifer, 18 cases with different hydraulic gradients, hydraulic conductivities and bathymetries were defined. All of these cases were run under three different scenarios in sequence. First, steady state scenario is preformed, then the lake level... 

Having information about the amount of water storage is essential to estimate the amount of water available for use in agriculture, industrial, etc. The purpose of this study is to propose a method for estimating the water budget in large-scale basins using remote sensing data. Using ground-based measurements to obtain water budget components is a challenging issue. This may be due to the limited access to in-site data in temporal and spatial resolution, especially in large scale basins. In recent years, with the increasing growth of satellite data, the application of remotely sensed data to estimate changes in water storage is increasing. In this study, due to the limitation of access to... 

Dense non-aqueous phase liquid accounts for a large share of groundwater pollution. In oil-rich countries, including Iran, the emission of this type of pollutant is mainly through leakage from concrete and steel tanks belonging to refineries and gas stations. The dissolution of these pollutants in groundwater and the vapor intrusion into residential homes increased the importance of developing efficient treatment methods. To choose the best method, it is necessary to gain sufficient knowledge of how these types of contaminants are distributed in the subsurface and how contaminants change and move over time. Heterogeneity, especially in the form of fracture, is one of the challenges to... 

Within the past few years, soil and groundwater resources contamination by petroleum-based products has become of great concern in the environmental engineering literature as a serious environmental problem throughout the world. Amongst petroleum hydrocarbons, groundwater contamination by Non-Aqueous Phase Liquids (NAPLs) is one of the most important environmental problems. In order to effectively remediate contaminated sites, knowledge of the distribution of the NAPLs is essential. The success of the remedial design will be dependent on the ability to predict the subsurface distribution of the NAPLs. Release of these compounds from spills and leaky underground storage tanks into subsurface...