A note on the analysis of groundwater travel times for injection–abstraction doublets

The solutions of Lippmann and Tsang (1980, Ground Water , 18, 452–458) for the temperature changes in an injection-abstraction doublet have been revisited as benchmarks for numerical simulations developed to assess the feasibility of open-loop geothermal systems. The Lippmann–Tsang solution for the evolution of the temperature at the abstraction well was developed for the case of no ambient groundwater flow in an aquifer that is sealed across its top and bottom. The results of testing confirm some puzzling aspects of the solution. In this note, it is shown that while some elements of the Lippmann–Tsang solution are correct, results for the temperature history at an abstraction well deviate substantially from solutions presented elsewhere in the literature.