Hfam II is based on the Stanford, HSP, HSPF, SRFM and Seafm family of models. It is a continuous simulation model that does historical or forecast analysis and it includes probabilistic or ensemble forecasts of streamflows, reservoir levels and releases or power production.
Hfam II uses and or simulates physical ‘elements’ in time. These elements are;
Meteorological Station Data – precipitation, actual evapotranspiration, wind, solar radiation, air temperature, and (optional) lapse rates
Streamflows, aquifer levels, snow course measurements, reservoir levels
Diversion demands, instream flows, minimum or maximum reservoir content, reservoir or reach seepage, irrigation applications, pumping from aquifer elements, hydro power demand, minimum and maximum streamflows below reservoirs, atmospheric loading
Low Level Outlets
The number of physical elements in a watershed is unlimited. Simulation runs hourly.
Figure 1 Hfam II Operations, Main Screen
Hfam II does four types of ‘runs’;
Forecast runs are made with deterministic weather forecasts, and are often used for flood forecasts and flood operations.
Analysis runs are made using historic and real-time data for model parameter calibration and for period of record studies of reservoir operations or water yields.
Probabilistic runs (also called Ensemble runs) give exceedance probability for watershed and reservoir conditions in the future based on the current watershed state and future weather.
Optimization runs solve for the current optimal release from a reservoir given current and future values of releases and exceedance probabilities for reservoir inflows.
Meteorological time series inputs for Hfam II are stored in three data bases; forecast, historic and real-time. These data bases can be seamlessly connected in any model run.
Output from Hfam II includes flows and storage in physical elements, heat exchange, and mass and concentration for sediment and nutrients. Statistical summaries of both inputs and outputs are available. Model input and output are in XML, and all model inputs can be verified with Schemas before they are used by the model.
Model outputs are available for all time series. Any XML conversant program, like EXCEL or WORD can use these outputs directly.
Examples of model screens follow:
Figure 3 Snowpack Conditions at Alpine Meadows Snotel
Figure 4 Heat Exchange at Alpine Meadows Snotel
Figure 5 Vegetation, Soil and Groundwater Storages
Figure 6 Precipitation and Soil Moisture Flux
Figure 7 Simulated and Observed Streamflows
Figure 8 Simulated and Observed Streamflow Summary Data
Figure 9 Watershed Summary Data, Cumulative above Reaches or Reservoirs
Figure 10 Exceedance Probability for Cumulative Conditions above a Reach or Reservoir
Figure 11 Flood Frequency
Figure 12 Historical Snowpack Water Equivalent, Period of Record ( selected weather year in red)
Figure 13 Watershed Soil Moisture Probability
Figure 14 Watershed Snow Water Equivalent Probability
Figure 15 Aquifer Segment Storage, Inflow and Outflow
Figure 16 Aquifer Segment Storage Probability
Figure 17 Reservoir Levels and Frequency Data
Figure 18 Reservoir Operations
Figure 19 Reservoir Operations, Demands and Release
Figure 20 Powerhouse Demand and Generation
Figure 21 Reservoir Elevation, Period of Record (selected weather year in red)
Figure 22 Optimization Detail at a Reservoir
Figure 23 Interactive Parameters and Files, Reservoir
Figure 24 Meteorological Time Series Linkages
Figure 25 Input Time Series, Air Temperature
Figure 26 Data Availability Summary (maintained by Hfam II)
Figure 27 Instream Flow Specification
Snow Water Equivalent,
Snow Water Equivalent Detail,
Hfam II is a comprehensive modeling system that simulates hydrologic processes (runoff from rainfall and snowmelt, channel flow) and the operation of existing or planned water resource facilities (reservoirs, hydro plants, irrigation systems).
Hfam II is use for both design and operation of projects. For design, proposed facilities are added to a watershed and the operation of the facilities is explored. This allows comparison of project alternatives, and economic analysis of reservoir characteristics, hydroplant capacities, diversions, and other facilities. Output from Hfam II can be loaded directly into Excel, Word, and other programs. 
Hfam II does historic analysis, forecasts, probabilistic and optimization runs. When used for operation of projects, Hfam II shows future reservoir outflows, irrigation diversions, conditional flood frequency, and reservoir elevation probability.
History and Applications
Many concepts in the system were first explored in research
Model applications in
Middle Fork Nooksack,
Saco, Androscoggin, and
Model applications in
Rio Paranaiba, Brazil, Embocacao Hydroelectric project, spillway design
 Hfam II uses XML input and output. Historic, real-time, and forecast data bases are maintained.
 Predecessor models are the Stanford Watershed Model IV (1966), HSP (1972), HSPF (1980), SRFM (1987), SEAFM (1990), and HFAM 1.1 (1997). These models have been applied in thousands of watershed worldwide.