ANALYZING FLOW DIRECTION AS A CALIBRATION TARGET IN GROUNDWATER FLOW MODELS

In groundwater flow models, hydraulic conductivity values are calibrated so that model outputs closely match what is observed in the real world. This calibration process traditionally uses field hydraulic head measurements as the calibration target. Previous research has examined using differences in head between wells as a target and touched briefly upon flow direction. While typically not used, tools exist to allow for flow direction to easily be measured down a well. This research aims to determine if this additional data is useful for the calibration of groundwater flow models using new types of information from existing wells. We constructed synthetic, steady-state groundwater flow models in a 2-dimensional, heterogeneous aquifer using the USGS finite-difference flow model MODFLOW. The result of these synthetic models is hydraulic head and flow direction data. Using the Parameter Estimation Code-PEST, we blindly calibrated these synthetic models three times using hydraulic head, flow direction, and a hybrid of head and flow direction. We then analyzed error and uncertainty in the calibration to determine if flow direction is a useful calibration target alone or when combined with hydraulic.