  In this work we develop an a posteriori error estimator for mixed finite
element methods of Darcy flow problems with Robin-type jump interface
conditions. We construct an energy-norm type a posteriori error estimator using
the Stenberg post-processing. The reliability of the estimator is proved using
an interface-adapted Helmholtz-type decomposition and an interface-adapted
Scott--Zhang type interpolation operator. A local efficiency and the
reliability of post-processed pressure are also proved. Numerical results
illustrating adaptivity algorithms using our estimator are included.
