Monday, November 13, 2006

Estimating the Hydraulic Properties in Hanford Based on Water Table Variation.

Fred Zhang and Andy Ward. Pacific NW National Lab, Pacific NW National Lab, P.O. Box 999, Richland, WA 99352

Field-scale hydraulic properties are needed for simulation and prediction of the movement of flow and contaminant transport in the Hanford Site. The Hanford site is located by the Columbia River and generally the groundwater flow moves towards the river. The river water level shows both seasonal and diurnal variations and hence the groundwater also shows similar variation with a delay of the peak occurrence time and a reduction of variation amplitude in the inland. The response of inland water table to river level fluctuation is related to the hydraulic properties of the aquifer. After assuming the aquifer being homogeneous between adjacent wells, an analytical method was used to estimate the hydraulic conductivities. The hydraulic conductivities of geological units were also estimated using an inverse method. Consistent results were obtained from the two methods. The advantage of the analytical method is its ease of use and its requirement of less information; the disadvantage is that the system must be homogeneous. The advantage of the inverse method is its capability to provide filed-scale hydraulic properties for a heterogeneous system; disadvantage is that the process is more complex and generally needs more data. The Pacific Northwest National Laboratory is operated for the U.S. Department of Energy by Battelle under Contract DE-AC05-76RL01830.