1.   Purpose and objectives

     PC-IHACRES v1.02 is a software package that allows simulation of continuous streamflow using only time series of rainfall, streamflow and air temperature. Except for the area of the catchment, no other landscape descriptive information is required. Unit hydrographs (UHs)for total streamflow and, in many cases, its dominant quick and slow response components, can be identified. In such cases, the
modelled continuous hydrograph is the sum of dominant quick and slow response hydrographs, and a Slow Flow Index (SFI) is calculated. The package can assist with (a) projects/research at tertiary- and post- graduate levels, (b) operational hydrology (e.g. infilling missing flow data, data quality assurance), and (c) advanced research related to environmental change impacts on hydrological regimes,
regionalization, etc.

2.   Description

     PC-IHACRES v1.02 is a Windows compatible software application with Windows-style menus and dialogue boxes. A comprehensive User Guide, with tutorials, is supplied to help the user learn how to
apply the methodology. The only data needed for input are good quality time series of basin rainfall and streamflow and, for modelling over long periods, an index variable for evapotranspiration (usually air temperature, but pan evaporation can also be used).

     The model has two modules: a non-linear conversion of rainfall to effective rainfall; and a linear conversion of effective rainfall to streamflow (the UH module). The UH module structure is flexible,
allowing the operator to select either a single linear storage, or two storages in series, or two storages in parallel. The complete model with two linear storages in parallel in the UH module, which often proves to be optimal, has just 6 parameters.

3.   Input

     When using an index variable for evapotranspiration there are two ASCII data files: a file containing columns of observed rainfall and streamflow at regular time intervals; and a file containing index data such as air temperature. Other information required for modelling, such as catchment area, rainfall and streamflow measuring units, data time step, period of record for analysis etc., are input via menus and dialogue boxes and can then be stored for future use.

4.   Output

     A summary file of model results appears on the screen automatically after each run (calibration or simulation).There is a range of operator-selected graphical displays (which can be hardcopied), and a main output file of results. The observed and modelled time series, and the UH ordinates, can be exported to files.

5.   Operational requirements and restrictions

     An IBM PC compatible computer with MicroSoft Windows 3.1 or higher and MS-DOS 5.0. The minimum requirements are an 80386 processor (with maths coprocessor), 4MB of RAM and VGA
graphics. However, a 80486DX50 with at least 8Mb and SVGA and with a minimum of 1Mb of video RAM is recommended. Any printer which supports Windows can be used.

6.   Form of presentation

     Downloadable software with a comprehensive user manual, demonstration data sets and tutorials.

7.   Operational experience

     The IHACRES methodology has been successfully applied to catchments with basin areas ranging from 90 m2 (6-minute interval data) to nearly 10,000 km2 (monthly data). There are many published
accounts of the methodology and demonstrations/discussions of its applications, including: characterization of the quick and slow flow dynamics of hydrological regimes; hydrograph separation; assessing the impacts of land-use change; regionalization. While PC-IHACRES v1.02 is applicable over a wide range of catchment types it is not suitable for all hydroclimatic situations. Training courses for
PC-IHACRES v1.02, and advanced application of the IHACRES modelling approach, may be arranged.

8.   Originator and technical support

     PC-IHACRES v1.02 was developed jointly by the Centre for Ecology and Hydrology, Wallingford, UK and the Centre for Resource and Environmental Studies at the Australian National University,Canberra. There is no formal technical support. It may be possible, however, to respond to queries in some cases (though there is no guarantee that a given query will receive a response).

9.   Availability

     The software, its 94-page User Guide and other documentation are downloadable, free of charge, clicking here or from the CEH website.

10.  Conditions on use

     Please read all of the information downloaded with the package. Neither CEH nor ANU accept any liability for how results obtained using the package are applied.