SPECTRAL HYDROLOGY FOR REGIONAL MODELING EFFORTS

Regional groundwater models are most commonly tuned under what are assumed “steady state” conditions, as transient modeling and parameter estimation still incur both significant numerical cost and data management efforts. However, many regions are influenced by periodic boundary conditions, forcings, or sources, including (in order of increasing frequency): annual precipitation variability, annual temperatures, tidal signals, earth tides, atmospheric fluctuations, daily pumping signals, and evapotranspiration. These signals suggest the utility of a numerical modeling framework that takes advantage of repeated forcings and simulates the propagation of signals’ amplitude and phase delay throughout a modeled aquifer. In this presentation, we demonstrate such a modeling approach using a fast, steady-periodic modeling framework, or “spectral hydrology”. This modeling framework simulates periodic forcings of realistic, heterogeneous regional aquifers using a MODFLOW-style framework. We discuss conditions under which these models are appropriate as well as how these models can influence understanding of dynamic processes such as capture zone variation, transient mixing, and surface water-groundwater exchanges.