Abstract
The flood-wave method is implemented within the framework of time-series analysis to estimate aquifer parameters for use in a groundwater model. The resulting extended flood-wave method is applicable to situations where groundwater fluctuations are affected significantly by time-varying precipitation and evaporation. Response functions for time-series analysis are generated with an analytic groundwater model describing stream–aquifer interaction. Analytical response functions play the same role as the well function in a pumping test, which is to translate observed head variations into groundwater model parameters by means of a parsimonious model equation. An important difference as compared to the traditional flood-wave method and pumping tests is that aquifer parameters are inferred from the combined effects of precipitation, evaporation, and stream stage fluctuations. Naturally occurring fluctuations are separated in contributions from different stresses. The proposed method is illustrated with data collected near a lowland river in the Netherlands. Special emphasis is put on the interpretation of the streambed resistance. The resistance of the streambed is the result of stream-line contraction instead of a semi-pervious streambed, which is concluded through comparison with the head loss calculated with an analytical two-dimensional cross-section model.
Highlights
The development of methods to estimate aquifer parameters from stream–aquifer interaction dates back to the 1960s and the early application of computers in hydrology (Cooper and Rorabaugh 1963; Pinder et al 1969; Venetis 1970)
The approach proposed at that time, referred to as the flood-wave method, is similar to a pumping test, as the groundwater head in an aquifer is perturbed by a single stress, in this case a flood wave in a stream adjacent to the aquifer
Groundwater heads are calculated with MicroFEM as suggested by Olsthoorn (2008) by first evaluating the step responses at the place of the piezometers, after which head fluctuations are obtained by convolution of the block response functions with their corresponding stress time series
Summary
The development of methods to estimate aquifer parameters from stream–aquifer interaction dates back to the 1960s and the early application of computers in hydrology (Cooper and Rorabaugh 1963; Pinder et al 1969; Venetis 1970). The approach proposed at that time, referred to as the flood-wave method, is similar to a pumping test, as the groundwater head in an aquifer is perturbed by a single stress, in this case a flood wave in a stream adjacent to the aquifer. The aquifer diffusivity is obtained by fitting a simple equation for stream–aquifer interaction to the observed heads. This equation fulfills the same function as the well functions of pumping tests. Hall and Moench (1972) refined the method by using convolution integrals to relate stream stage fluctuations and head fluctuations. Moench and Barlow (2000) extended the method by adding equations for a set of different stream–aquifer configurations. Groundwater head response to a time series of stream stage fluctuations can be obtained analytically by replacing the time series of observed stream stage by a series of basis splines (Knight and Rassam 2007; Rassam et al 2008)
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