This chapter considers the gene expression programming (GEP), different types, and developments of GEP-based techniques in hydroinformatics. The genetic programming (GP), linear genetic programming (LGP), GEP, multigene genetic programming, tree-GEP, and pareto-optimal multigene genetic programming are introduced, and their applicability in various fields of hydraulic and hydroinformatics is discussed. The results of the case studies of GEP-based models confirmed the accuracy and suitability of these techniques in various aspects of hydraulic and hydrology models. Several function findings using GEP-based methods in hydraulic and river engineering are performed, and their explicit equations are derived as a strength model induction engine. The results of the case studies confirmed the general aspects and accuracy of GEP in function findings.