  The aim of this work is to design implicit and semi-implicit high-order
well-balanced finite-volume numerical methods for 1D systems of balance laws.
The strategy introduced by two of the authors in a previous paper for explicit
schemes based on the application of a well-balanced reconstruction operator has
been applied. The well-balanced property is preserved when quadrature formulas
are used to approximate the averages and the integral of the source term in the
cells. Concerning the time evolution, this technique is combined with a time
discretization method of type RK-IMEX or RK-implicit. The methodology will be
applied to several systems of balance laws.
