Two-parametric families of Riemann surfaces and their degenerations

In this talk we consider semi-Hamiltonian hydrodynamic type systems and corresponding Riemann surfaces. We illustrate our construction by the generalised chromatography system, whose Riemann surface depends on two parameters. In the special limit this hydrodynamic type system can be written explicitly via Riemann invariants, which are nothing but branch points of the corresponding Riemann surface. We discuss the limit and generalisation of hyperelliptic algebraic curves.