The application of modified fuzzy least-squares regression for estimation of hydrodynamic coefficients by the Cooper-Jacob method (Case study: Sohan plain)

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.