The Precipitation-Runoff Modeling System is a deterministic, distributed-parameter, physical process based modeling system used to evaluate the response of various combinations of climate and land use on streamflow and general watershed hydrology.  Response to normal and extreme rainfall and snowmelt can be simulated to evaluate changes in water-balance relations, streamflow regimes, soil-moisture relations, and groundwater recharge. Each hydrologic process is represented within PRMS by an algorithm that is based on a physical law or an empirical relation with measured or estimated characteristics.
Distributed-parameter capabilities are provided by partitioning a watershed into hydrologic response units (HRUs) that are based on the physical attributes of the watershed such as land-surface elevation, slope and aspect, vegetation type, soil type, and spatio-temporal climate patterns. The physical attributes and hydrologic response of each HRU are assumed to be homogeneous. A water balance and an energy balance are computed daily for each HRU. The sum of the responses of all HRUs, weighted on a unit-area basis, produces the daily watershed response in the most basic configuration. In addition, PRMS can provide more sophisticated methods of internal routing that are available for more complex modeling applications.

Website:  https://wwwbrr.cr.usgs.gov/projects/SW_MoWS/PRMS.html

GSFLOW was developed to simulate coupled groundwater/surface-water flow in one or more watersheds by simultaneously simulating flow across the land surface, within subsurface saturated and unsaturated materials, and within streams and lakes. Climate data consisting of measured or estimated precipitation, air temperature, and solar radiation, as well as groundwater stresses (such as withdrawals) and boundary conditions are the driving factors for a GSFLOW simulation. GSFLOW can be used to evaluate the effects of such factors as land-use change, climate variability, and groundwater withdrawals on surface and subsurface flow for watersheds that range from a few square kilometers to several thousand square kilometers, and for time periods that range from months to several decades.

Website: https://water.usgs.gov/ogw/gsflow/

WISTOO is an Integral distributed mathematical model used for (1)  runoff hydrograph simulation at arbitrary valley cross-section, (2) spatial visualization of hydrological processes and (3) determination of influence of water reservoirs on runoff hydrograph from watershed.  It is an Integral distributed model based on hydrodynamic equations describing processes: infiltration,
surface runoff, subsurface runoff and water transformation in river network. Interception and groundwater runoff are described by simplified formulas. Evapotranspiration process is solved
depending on meteorological input data, as Penman-Moteith equation, empirical function or tabular values.  The optimal spatial scale varies between 10m x 10m and 25m x 25m for one cell (calculation element) whereas the basic calculation time step is 1 hour. For small watersheds 10 minute time step can be applied

Description:  WISTOO.pdf         Contact:  Dr Wieslaw Gadek (wieslaw.gadek@iigw.pl)                                                                                                                                                                                                          _____________________________________________________________________________________________________________________________________

CASC2D is a square-grid (raster) hydrologic model that solves the equations of transport of mass, energy, and momentum between model grid cells using a finite difference formulation. The model can be used in the simulation of spatially-varied Hortonian watershed hydrology and erosion/sediment transport. CASC2D can be run in a single-event mode, or in continuous mode. Continuous simulations can be run for an indefinite period of time. Model computational time-steps for numerical stability range from 1 second to 20 seconds, depending upon the grid size and rainfall intensity.

Description:  CASC2D.pdf.    Website: https://www.engr.colostate.edu/CASC2D

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BWBM is a spatially distributed continuous soil moisture accounting and precipitation/snow-melt runoff simulation model. The model is intended for mesoscale (approx. 100-10000 sqkm) watersheds. The model continuously simulates stream flow and all components of the water balance on a spatially distributed basis at a daily time step.

Model Description: BOCHUM.pdf   Contact:  dgaren@wcc.nrcs.usda.gov or Andreas.Schumann@ruhr-uni-bochum.de

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ArcGMO is a deterministic 3D-catchment, multilayer model used to predict components of the water budget in small and large watersheds . The model uses digital maps for describing the spatial characteristics of the research area (elevation, aspect, slope, soil, land use/land cover, groundwater depth) and time series of precipitation, air temperature, air humidity, global radiation or sun duration and wind velocity as inputs and generates time series of stream flow, other budget components, carbon and nitrogen budget components, vegetation variables, results of the climate regionalization among others that can be imported easily into GIS (e.g. ArcView, ArcGIS) or into table calculation programs (EXCEL, ACCESS etc.)

Model Description: ArcEGMO.pdf.   Website:  http://www.arcegmo.de/

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