1.   Purpose and objectives

     The HBV Model is a computerized catchment model that converts precipitation, potential evaporation, and snowmelt, if applicable, into stream flow/reservoir inflow by simulating of the natural hydrological processes.

     It is part of a computerized system for hydrological forecasting, discharge simulation, design flood computations and climate change studies, the HBV/IHMS (Integrated Hydrological Modelling System). Special versions of the model (HBV-N and PULSE) can be used for simulation of water quality, 
e.g. nitrogen, pH, and alkalinity.

2.   Description

     The model includes a snow accumulation and snow melt routine, a soil moisture accounting routine, a groundwater routine, and a routing procedure.

     Standard HBV model routes generated runoff by combining e.g. Muskingum with an additional Lag-function. Routing through lakes is done by level- pole routing, in case of regulations, reservoir operation strategies in very complex systems of reservoirs can be taken into account.

     The most important parameters are estimated through a calibration procedure, which generally requires 3 to 5 years of simultaneous streamflow and meteorological records.

     If there are no stream flow records available, the parameters can, in some cases, be estimated from known basin characteristics.

3.   Input

     Precipitation totals - and in case of snowfall also mean air temperature for the time-step used - and potential evapotranspiration.

     The HBV/IHMS software can handle any of the following time steps: 24, 12, 6, 4, 3, 2, and 1 hours.

4.   Output

     The modelling system has extensive graphical presentation facilities. Various methods of checking data before calibration, simulation or forecasting can be applied. Printed or plotted output includes 
precipitation, recorded and computed streamflow, accumulated differences between recorded and computed streamflow, computed soil moisture, snow accumulation, snow melt, and evaporation as well as statistical analyses of results.

5.   Operational requirements and restrictions

     The core program of the simulation model is written in FORTRAN, whereas a graphical user interface  (GUI) under Windows 95/NT is used on PC platforms.

     Installation and modification of the program needs professional personnel with specialized training.

6.   Form of presentation

     Users' manual in English plus diskette or CD with software programs.

7.   Operational experience

     The HBV Model has been in real-time operation for streamflow forecasting since 1977. It is now the standard forecasting tool in Sweden, where some 50 catchments are calibrated for the national warning services, mainly in small and unregulated rivers. Forecasting for the hydropower companies are made in an additional 70 catchments. In addition operational or scientific applications of the HBV-model are known from more than 40 countries around the world.

     Participation in the two WMO projects, Intercomparison of models of snowmelt runoff (1977-83) (ref: O.H. Report No. 23 Intercomparison of models of snowmelt runoff, WMO No. 646), and Simulated realtime  intercomparison of hydrological models (1986-89) (WMO O H Report No. 38, 1992), has given additional experience of runoff modelling in a number of hydrological basins in Europe, United States, and Canada (areas 8.4 Km2 to 2300 Km2). The model has been applied to catchment areas ranging from less than 1 Km2 to over 30000 Km2. The use of the model is well documented.

8.   Originator and technical support

     The HBV Model and the HBV/IHMS software has been developed at the Swedish Meteorological and Hydrological Institute (SMHI).

     Technical support is provided by the SMHI.

9.   Availability

     Swedish Meteorological and Hydrological Institute (SMHI) SE-601 76 Norrköping, SWEDEN

10.  Conditions on use

     To be negotiated in each case.