Fractal Fluctuations of Groundwater Levels: Numerical Simulations

Numerical simulations were carried out to study temporal variations and scaling of the water table fluctuations in one- and two-dimensional unconfined heterogeneous aquifers under spatially and temporally varied groundwater recharge. The recharge process was taken to be either a white noise or temporally and spatially correlated process and field with an exponential covariance function. The results were compared with the observed water levels in monitoring wells as well as the theoretical results derived using non-stationary spectral methods and the detrended fluctuation analyses. The simulation results further verify the findings in our previous studies that scaling of groundwater levels does exist in many aquifers and that the hydraulic head in an aquifer may fluctuate as a temporal fractal in response to a white-noise or stationary or a fractal recharge process, depending on how quickly the hydraulic head responds to recharge events and the physical parameters of the aquifer (i.e., transmissivity and specific yield). The recharge process at the Walnut Creek watershed was shown to have a white-noise spectrum based on the observed head spectrum. The effect of aquifer heterogeneity on the water level fluctuations and scaling was also investigated and will be presented in the meeting.