The analysis of pulse interference tests conducted in a fractured rock aquifer bounded by a moving free surface

An analytical model is presented for the analysis of pulse interference tests conducted in a fractured porous medium with connection to a free surface boundary at the water table. The solution is applicable to open borehole pulse interference tests due to the accommodation of multiple horizontal fractures intersecting each wellbore and a connection from the uppermost horizontal fracture via a network of vertical fractures to a free surface boundary. The solution is derived using the Laplace transform method and evaluation of the solution is performed by numerical inversion. Based on an informal analysis, the model is sensitive to transmissivity, storativity, specific storage, vertical hydraulic conductivity and particularly specific yield over a range of realistic values for these parameters. A field example is presented to illustrate the application of the model in the estimation of specific yield in fractured rock settings with relatively low vertical permeability. Although a reasonable model fit was obtained, application to an additional field example having only one fracture was unsatisfactory, and further study on uniqueness is warranted.