جستجوی مقالات مرتبط با کلیدواژه « hydrodynamic coefficients » در نشریات گروه « زمین شناسی »

Groundwater is one of the main sources of water supply for agriculture, drinking and industry in Iran, especially in areas with arid and semi-arid climates. Therefore, due to the high importance of groundwater resources, it is necessary to know the hydrodynamic parameters in order to determine the natural flow of water and manage the optimal utilization of groundwater resources. Considering the role of the Daloon-Meydavood aquifer in providing part of the water needed in the study area, especially for agricultural purposes, the hydrodynamic parameters of this aquifer were estimated using the methods of grain size analysis, geophysics and pumping test. The parameters were calculated by all three methods and validated using the flow rate of the exploitation wells. In all three methods, the hydrodynamic parameters (Hydraulic conductivity, Specific yeild, transmissivity coefficient) are the highest in the north and northeast and the lowest in the south and northwest. The results showed that 2 methods including  grain size analysisand pumping test had the most similarity with the discharge map of the exploitationwells.

One of the most important concerns in aquifers adjacent to oil facilities is pollution caused by LNAPL leaks. Because these compounds have less weight than water, they float on the surface of the water as a layer and move along with the water flow. Recovery of LNAPLs is always difficult and expensive. This study aims to manage the recovering costs by determining the hydrodynamic coefficients of LNAPL. The hydrodynamic coefficients include transmissivity and specific yield. In this study, for the first time, instead of the term specific yield, the term oil specific yield has been used according to the type of fluid in the aquifer. The Rockwork model was used to calculate the oil specific yield and LDRM (LNAPL Distribution and Recovery Model) model was used to calculate LNAPL transmissivity coefficient. The inputs of the LDRM model include soil and LNAPL parameters, porosity, hydraulic conductivity of water saturation, van Genuchten parameters, mass densities of water and LNAPL, surface tensions of water-LNAPL, LNAPL-air and water-air, viscosities of water and LNAPL. From the inputs, LNAPL transmissivities and recoverable and total LNAPL specific volumes were extracted as output results. With the help of the obtained results, maps of LNAPL transmissivities, thickness and recoverable volume of LNAPL were prepared and the best recovery locations were introduced.

Hydraulic conductivity and Specific storage are known as the most important hydraulic characteristics of aquifers. Recently, due to software advances, the use of numerical models in the operation of groundwater aquifers has expanded. Modeling is one of the best tools for studying and simulating the state of water resources. One of the advantages of modeling is the simultaneous determination of several parameters such as hydraulic head, flow path and etc. Likewise, via modeling, it is possible to simulate the reaction of the basin against changes such as natural or artificial recharge and the amount of pumping, and by applying appropriate solutions, determine the best performance of the system then use it to manage the basin. In the present study, MODFLOW numerical model and GMS user interface were utilized to simulate and calibrate the model. Accordingly, the hydrodynamic properties of the Shabestar plain aquifer were evaluated regionally. As a result, the RMSE values of hydraulic head for the steady-state and non-steady-state models were 0.59 (m) and 0.95 (m), respectively. The obtained results demonstrated that the more heterogeneous the aquifer, the more diverse the hydrodynamic coefficients will be, and this variation does not follow a specific trend due to the existence of geological formations, the density and the porosity of the formations.

Estimation of aquifer hydrodynamical parameters is one of the important issues in groundwater resource management. It is essential to determine the aquifer's hydraulic properties in order to understand and recognize the natural flow pattern of an aquifer and groundwater measurement. As aquifer characteristics, transmissivity and the storage coefficient may vary spatially due to the existence of different subsurface materials, resulting in geological heterogeneity. Assessment of transmissivity and the storage coefficient, as the most significant hydrodynamical parameters, allows for a quantitative prediction of aquifer response to recharge and discharge rate. There are many different methods for hydrodynamical parameter estimation, which include a variety of methods such as: empirical formulas, laboratory methods, geophysical methods, tracking experiments and pumping tests. However, among all these techniques, the application of pumping test data is the most useful and common method, with the ability to reflect a wide range of aquifer. Using drawdown-time pumping test data can calculate the aquifer parameters which is able to employ different methods. The Cooper Jacob equation is used to determine the transmissivity and the storage coefficient for a confined aquifer using pump test results. In this research, a modified fuzzy least-squares regression (MFLSR) method uses imprecise pump test data to obtain fuzzy intercept and slope values which are then used in the Cooper Jacob method. Fuzzy membership functions for the transmissivity and the storage coefficient is then calculated using the extension principle. The modified fuzzy least-squares regression that is coupled with the Cooper Jacob method allows the analyst to ascertain the uncertainty that is inherent in the estimated parameters in an aquifer.