Abstract The exact solutions of nonlinear partial differential equations are significant to analyze the soliton nature of physical phenomena. Therefore, the Lie symmetry method is introduced to obtain exact solutions of the Broer-Kaup-Kupershmidt system. It represents two-dimensional propagation of nonlinear and dispersive long gravity waves in shallow water with uniform depth. The present work is devoted to derive symmetry reductions, soliton solutions, and conserved vectors under one-parameter Lie group transformations. Meanwhile, the invariance property of Lie groups validates the reducibility of the system. Therefore, a continual process of reductions transmutes the test system into a system of ordinary differential equations. Thus, this integrability property leads to generalized exact solutions with parametric constraints. These solutions entail all three arbitrary functions, f 1(y), f 2(t), f 3(t) existing in infinitesimals and various free parameters. On account of existing functions and free parameters, the obtained solutions are more admirable than those of preceding works (Kassem and Rasheed 2019 Chinese J. Phys. 57 90–104, Kumar et al 2022 Math. Comput. Simulat. 196 319–35, Tanwar and Kumar 2024 J. Ocean Eng. Sci. 9 199–206) and helpful to describe significant physical nature under wide parametric ranges. The deductions of previous results on imposing the particular values to arbitrary functions and constants ensure the generalness and novelty of derived results. Moreover, adjoint equations and conserved quantities associated with Lagrangian formulation have been evolved via Lie symmetries. We numerically simulate these solutions to analyze their physical nature. Consequently, soliton fusion and fission, line solitons, doubly solitons, multisolitons, and bright and dark soliton nature are discussed, which validate the physical relevance of the solutions.
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