HYDRAULIC PARAMETERS AND GROUNDWATER FLOW PATTERNS IN THE OREGON CASCADES, DETERMINED USING NUMERICAL MODELS THAT ARE CONSTRAINED BY DIVERSE DATA SETS

Determination of hydraulic properties as well as rates and patterns of groundwater flow in geologically complex volcanic aquifer systems often requires utilization of multiple complementing data sets, such as standard hydrogeologic data, subsurface temperatures, and noble gas abundances that provide constraints for numerical models. To enable simulations to utilize these diverse data sets, the numerical models must be capable of simulating the relevant coupled processes such as coupled groundwater, heat, and noble gas transport. Furthermore, the temporal and spatial scales over which these processes act are likely different which can allow investigation of variations in hydraulic properties and groundwater flow patterns and rates over a range of scales.

Permeability fields and groundwater flow patterns in the Oregon Cascades are presented that were obtained from analytical and numerical models constrained by hydrologic, thermal, seismic, magmatic, and noble gas data. Also discussed is the scale dependency of these results and the way in which permeability may change as a function of depth in the Cascades (and possibly in continental crust in general), and how groundwater flow, heat transfer, and noble gas patterns may differ between the western and the eastern slopes of the Oregon Cascades.