Effects of variations of river stage and hydraulic conductivity on temporal scaling of groundwater levels: numerical simulations |
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| Authors: | You-Kuan Zhang Xiaoying Yang |
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| Institution: | (1) Department of Geoscience, University of Iowa, Iowa City, IA 52242, USA;(2) Center for Hydroscience Research, Nanjing University, Nanjing, 210093, Jiangsu, China |
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| Abstract: | It was found in previous studies that groundwater levels may fluctuate as a temporal fractal. In this study numerical simulations
of groundwater level fluctuations in an unconfined aquifer near a river were conducted to investigate the effects of aquifer
heterogeneity and river stage variations on the fractal behavior of the water levels, h(t). Groundwater recharge was taken to be a white-noise process. The aquifer heterogeneity was simulated with a second-order
stationary field of hydraulic conductivity (K) with an exponential variogram model. The results showed that groundwater levels fluctuate as a temporal fractal in both
homogeneous and heterogeneous aquifers as long as K is less than 10 m/d. Most aquifers may indeed act as a fractal filter which takes a random non-fractal recharge inputs and
produces a fractal responses of groundwater level fluctuations. A crossover in temporal scaling of h(t) may appear in more permeable aquifers. Fluctuations of the groundwater level in a homogeneous aquifer are dominated by the
recharge process when the river stage is constant or by the river stage variations when the river stage varies in highly permeable
aquifers. Heterogeneity plays an important role in the temporal scaling of h(t) in more permeable aquifers: the stronger the heterogeneity, the stronger the temporal scaling of h(t). |
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