A Generalized Multistep Dynamic (GMD) TOPMODEL

There is a lack of Ordinary Differential Equation (ODE) formulations in numerical hydrology, contributing to the application canned adaptive timestep solvers; hence continued dominance fixed (e.g., Euler) techniques despite their fundamental problems. In this paper, we reformulate Dynamic-TOPMODEL into constraint-handling ODE form and use MATLAB's advanced ODE-solvers solve resulting system equations. For wider applicability, but based on existing research and/or first principles, developed Generalized Multistep Dynamic TOPMODEL which includes: iso-basin spatial discretization, diffusion wave routing, depth-dependent overland flow velocity, relaxing assumption water-table parallelism ground surface, power-law hydraulic conductivity profile, new unsaturated zone flux, reference frame adjustment. To demonstrate model calibrate it peat catchment case study, for also test sensitivity discretization. Our results suggest that (a) five-fold improvement runtime can result from timestepping; (b) additional discretization layer, as way further constrain information where needed, improves performance; (c) common-practice arbitrary Topographic Index (TI) substantially alters calibrated parameters. More objective physically constrained top-down) approaches TI classification may be needed.