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Shoreline variation and river deltas are among the most dynamic systems in marine environments. The related different variations in spatial and temporal scales play significant roles in land planning and different management applications. Modeling the dynamics of seashore of Boujagh National Park (BNP) which is located on the southern coast of the Caspian Sea in the Sefidrud Delta (SD), considering natural and anthropogenic factors, was the main objective of the current study. To achieve this goal, a combination of remote sensing data, historical data, and numerical simulations was utilized. The BNP covers an area of 3270 ha and includes two international wetlands, Boujagh and Kiashahr. In earlier periods, this area faced severe morphologic
Pollutant distribution is one of the most important challenges in the world. The governing equation of this phenomenon is the Advection-Dispersion-Reaction (ADRE) equation. It has wide applications in water and atmosphere, heat transfer and engineering sciences. This equation is a parabolic partial differential equation that is based on the first Fick’s law and continuity equation. The application of pollution transport mathematical models in rivers is very vital. Analytical solutions are useful in understanding the contaminant distribution, transport parameter estimation, and numerical model verification. One of the powerful methods in solving nonhomogeneous partial differential equations analytically in one or multi-dimensional domains
Using constant coefficients is an inefficient way to explain the details of the problem of pollutant transport. This is due to factors such as nonuniform geometry, discharge changes, flow velocity and dispersion coefficient variations. Previous studies indicate that the ratio of studies on pollutant transport in rivers is lower than those on the porous media. However, the relative complexity of the solution of the pollutant transport equation in rivers (especially in the case of variable coefficients) in comparison with porous media highlights the importance of focusing on the solutions for rivers environment. In this study, the one-dimensional equation of pollutant transport in the river with location-dependent variables (velocity, dispers
For many environmental projects and plans, it is necessary to model pollutant transport in rivers. Pollutant transport modeling is a complex phenomenon with multiple factors affecting it. The basic governing equation describing pollutant transport is advection–dispersion equation. There are two main parameters in this equation, namely, dispersion coefficient and flow velocity. In non-uniform flow regimes, these parameters are both spatially variable, therefore, solution of the advection–dispersion equation usually accomplished using numerical methods. Spatial variability of these parameters makes it hard to determine them, particularly for dispersion coefficient in which determining it for non-uniform flows using the corresponding formu
بحث شناسایی و بازیابی تابع شدت منابع آلاینده ناشناخته، یکی از مهمترین مسائل و چالشهای زیستمحیطی در رودخانهها است. ازاینرو لزوم بهرهگیری از روشهای مطمئن و دقیق جهت بازیابی اطلاعات مربوط به شدت زمانی و زمان رهاسازی آلودگی از منابع آلاینده در رودخانه اجتنابناپذیر است. در هرکدام از روشهای حل معکوس معادله جابهجایی-پراکندگی در رودخانه، محدودیتها و نقاط ضعفی وجود دارد، بنابراین روشی مورد نیاز است که علاوه بر دقت و ک
ConclusionsIn this study, in order to compare two common time integration methods, including RK-3 and Strang method, two models were implemented and used to simulate 1D and 2D flow problems. In the 1D dam break problem, which is an actual experimental test case, both models provide satisfactory results. However, at the beginning of the simulation when flow is completely fluctuating, the RK-3 method has a higher accuracy. But over time, by decreasing fluctuating, both models have identical results which are close to experimental data. In the 2D oscillation problem with an analytical solution, water boundary remains circular in different frequencies, which refers to the capability of both models to simulate 2D problems and indicates an approp
The paper presents a new approach to identify the unknown characteristics (release history and location) of contaminant sources in groundwater, starting from a few concentration observations at monitoring points. An inverse method that combines the forward model and an optimization algorithm is presented. To speed up the computation, the transfer function theory is applied to create a surrogate transport forward model. The performance of the developed approach is evaluated on two case studies (literature and a new one) under different scenarios and measurement error conditions. The literature case study regards a heterogeneous confined aquifer, while the proposed case study was never investigated before, it involves an aquifer-river integra
Pollutants are usually drained off imperceptibly and suddenly in the rivers, which can be of human or natural origin, thus finding information from contaminant source as quickly as possible is important to reduce damage. The pollutant is released by the Advection-Dispersion processes in the river. Therefore, information on contaminant release site and release time can be obtained using inverse solution of the Advection-Dispersion equation. The purpose of this study is to solve Advection-Dispersion Equation (ADE) reversely and to obtain information on the release time and time series data of pollutant concentration discharged into the studied rivers. In this research, the quasi-reversibility method is used to reverse the ADE. In this method,
The inverse transport problem is very difficult and challenging to solve due to some special characteristics, including the lack of solution, non-uniqueness and instability. Regarding to these complexities, usually some simplifications are made in solution process, which ultimately leads to identification methods that cannot be extended for real-world applications. This study aims to develop a practical method for pollution source identification in rivers under realistic conditions, which considers irregular cross-sections, unsteady flow and both physical and chemical transport processes. The stochastic framework of proposed method provides the possibility of estimation of source characteristics in greater time instances than available obse
In the present study, an inverse model was used to identify the location and functions of the intensity of unknown point sources in the river. In this research, the inverse solution of the advection-dispersion equation is carried out using a mathematical approach. The main objectives of this model are to identify the location of the pollutant in the presence of several sources in the river without any prior information from the sources in the entire mathematical framework. The strength point of the inverse model is that, by measuring the concentration-time curve from a few points, the source location can be obtained with the highest accuracy. Also, after finding the source location in the river, the functions of the intensity of the polluta