Principal Investigator: Lynn J. Torak (Hydrologist -U.S. Geological Survey)
Principal Investigator: Shahrokh Rouhani Ph.D (Newfields Inc)
Sponsor: GWRI
Start Date: 1991-06-01; Completion Date: 1991-06-01;
Keywords: Ground-water, Hydrogeology, Statistical Methods, Regional Analysis
Description:
The parameter estimation is a crucial phase of any ground water flow investigation, which determines the success or failure of the prediction process. The commonly used parameter-estimation approaches are based on various inverse procedures that in many instances prove to be inadequate. This report presents an advanced alternative approach which is based on the geostatistical co-estimation technique, known as co-kriging. The investigated parameters are: aqulfer transmissivity, piezometric head, and residual, which is defined as the computed minus the measured water level at a specified location. Values of computed head were obtained by using the MODular linite ~lement model (MODFE) of two-dimensional ground water flow. The data set was derived from a regional study of the Upper Floridan aquifer in southern Georgia. The initial results indicate that the log-transformed transmissivity and the uncalibrated residual are suitable for co-estimation. Direct kriging provides estimated maps for these variables, which are unbiased linear estimates with minimum variance of estimation. The co-kriging goes one step further by permitting the incorporation of measured values of both parameters in the estimation processes of each one. The results indicate that the co-kriged maps represent more spatial details with higher accuracy than their ordinary kriged counterparts. Considering the high cost of field tests in ground water investigations, the above more efficient co-estimation process offers an attractive alternative for parameter evaluation than previously used inverse procedures.