Coupled hydrology, weathering geochemistry and surface-process evolution in a parallel global landscape evolution model

Abstract. goSPL (Global Scalable Paleo Landscape Evolution) is an open-source, parallel, finite-volume landscape evolution model designed to simulate the co-evolution of topography, drainage and sedimentary basins from catchment to planetary scale over geological time. Here, I present the new capabilities which extend the model from a fluvial–hillslope–marine sediment-routing engine into a coupled surface-process, near-surface-hydrology and weathering-geochemistry framework. The principal additions are (i) an implicit Dupuit–Boussinesq water table and a generic capillary-fringe duricrust that armours erodibility (forming either in situ or, with a groundwater-discharge gate, by lateral accumulation confined to valley discharge zones) and is archived in the stratigraphic record; (ii) a mass-conservative solute geochemistry module in which one or more lumped weathering tracers are dissolved, transported along the groundwater flux, precipitated as crust and routed down the river network to the ocean, with per-species typing, source provenance, spatially variable (lithology-controlled) weatherability and optional in-transit and marine coupling; (iii) a soil/regolith model; (iv) a mesh-native orographic-rain solver; (v) a diagnostic glacial-erosion model; and (vi) a parallel finite-volume flexural isostasy solver for planar meshes. All components are opt-in and are formulated as implicit or steady solves on a distributed PETSc DMPlex mesh, with solver choices (Krylov method, preconditioner, iteration scheme) driven by the conditioning of each operator. I describe the governing equations and the numerical and design choices behind each component, the YAML-based experiment configuration, the analytical-benchmark and regression test suite, and strong-scaling measurements on global production meshes of up to 23.7 million nodes. Finally I summarise the online documentation, the conda/PyPI/Docker distributions, the application interface and post-processing tools, and a suite of fifteen generic examples spanning regional and global scales. goSPL is distributed under the GNU GPL v3 licence.