Discussions on the special conditions satisfying “the Specific Well Yield is the Transmissivity”

To interpret the meaning of the specific capacity of a pumping well capturing lateral groundwater flow, Lan (2007) proposed an equation where the specific capacity is equal to the transmissivity(q=T) and shown evidences from hydraulic tests in sand boxes. However, the derivation of this equation was not on the robust basis of groundwater hydraulics. The boundary conditions of the sand-box tests were equivalent to a rectangular confined aquifer with one or two constant head boundaries. The steady state flow driven by a pumping well in these conditions could be solved with the superposition method on imaging wells. It reveals that the specific capacity is proportional to the transmissivity and the coefficient is subject to the aquifer shape and the radius of the pumping well. In some conditions, q=T could be caused by the special geometric characteristics of the aquifer-well system. The hydraulic tests in sand boxes presented in Lan (2007) just satisfied such special conditions but did not indicate that q=T is generally applicable. New tests in sand boxes without these special geometric characteristics have shown significant different results from the q=T equation.