SUFFICIENT CONDITIONS FOR IDENTIFYING TRANSMISSIVITY IN A CONFINED AQUIFER

It has been known for some time that the transmissivity T in a confined, steady-state aquifer Ω can be uniquely determined in the neighbourhood of sources and sinks even if Cauchy data on the characteristics are lacking. Recently Chicone and Gerlach extended this result to those regions of the aquifer that are not completely crossed by a characteristic line. In this letter we present an alternative characterisation of such regions that may be of more practical use. In particular we use a relatively straightforward technique to establish that for steady-state aquifers T is identifiable on a subdomain Λ of Ω provided that either (1) the head is constant on the boundary Λ or (2) the normal gradient /n does not change along Λ. Extension of those results to time-varying aquifers is provided.