HyPix: 1D physically based hydrological model with novel adaptive time-stepping management and smoothing dynamic criterion for controlling Newton–Raphson step

The newly developed open-source Hydrological Pixel model, HyPix, written in the fast and flexible Julia language, efficiently solves mixed form of Richardson–Richards’ equation (RRE). HyPix uses a cell-centred, finite-volume scheme for spatial discretization, with an implicit Euler temporal by using weighted average inter-cell hydraulic conductivity. includes following modules: (a) rainfall interception, (b) root water uptake compensation algorithm growth, (c) soil evaporation, (d) ponding novel method computing sorptivity, (e) runoff. wide range top boundary conditions (flux, pressure, free drainage). To control Newton–Raphson iterations, incorporates dynamic physical smoothing criterion, which improves not only model performance but also its accuracy compared traditional absolute convergence criterion. time-step, time-step management based on changes content was specifically designed to solve RRE content. This work adapts such that it is pressure without introducing further parameters. requires one parameter found be more efficient than management. implements option derivatives numerically, enabling modified tested (e.g., conductivity) changing few lines code. Numerically calculating as accurate deriving analytically, 10–25% slower. well-established hydrological HYDRUS used validate sink term. results show good agreement HYDRUS, validating algorithms implemented HyPix. Even challenging conditions, can provide reliable recommended standard options. Moreover, particularly coarse texture soils. options were running term field data.