ParFlow is a numerical model that simulates the hydrologic cycle from the bedrock to the top of the plant canopy. It integrates three-dimensional groundwater flow with overland flow and plant processes using physically-based equations to rigorously simulate fluxes of water and energy in complex real-world systems. ParFlow is a computationally advanced model that can run on laptops and supercomputers and has been used in hundreds of studies evaluating hydrologic processes from the hillslope to the continental scale. Our code is open source and we promote a community of active users and developers interested in advancing computational hydrology and improving hydrologic understanding. Details about the model, example applications and links for downloading and getting started with the code are provided below.

ParFlow is used extensively for water cycle research in idealized and real domains as part of process studies, forecasting analysis, data assimilation frameworks, hind-casting tools and climate change projections. The model has been extensively benchmarked and has more than 90 publications describing its development and application to diverse systems around the world. ParFlow applications have been built for the continental US (CONUS) and Continental Europe in addition to more than a dozen watersheds around the world including the Big Thompson, CO; Klamath, OR; Little Washita, OK; San Joaquin, CA; Sante Fe, FL; Chesapeake, MD; Rur as well as several headwater catchments, Germany.

ParFlow is a parallel, integrated hydrology model that simulates spatially distributed surface and subsurface flow, as well as land surface processes including evapotranspiration and snow. It solves saturated and variably saturated flow in three dimensions using either an orthogonal or terrain-following, semi-structured mesh that enables fine vertical resolution near the land surface and deep (~1 km) confined and unconfined aquifers. ParFlow models dynamic surface and subsurface flow solving the simplified shallow water equations implicitly coupled to Richards’ equation; this allows for dynamic two-way groundwater surface water interactions and intermittency in streamflow. The model uses robust linear and nonlinear solution techniques and exhibits efficient parallel scaling to large processor counts, more than 100K cores, enabling very large extent simulations with fine spatial resolution. ParFlow has been coupled to various land surface and atmospheric models such as CLM, WRF, and TerrSysMP.