IHACRES requires three sets of time series data. These are:

• observed rainfall (resolution defines the resolution of the model run)
• temperature (maximum preferred) or potential evapotranspiration (PET)
• observed streamflow.

Three timesteps are supported - minutes, hours and days. A typical calibration period is about 3 years, though it may need to be longer for ephemeral streams. These data must be in ASCII text format (comma, tab or space delimited).

Depending on the measurement units used for the datasets, catchment area (in sq kms) may be required.

• Visualisation of imported time series

• Visualisation of pre and post cross correlations for the linear module
• Table of post grid search summary statistics
• CSV output file of grid search summary statistics
• 3D visualisation of grid search parameters - contours and surfaces

• Charts and tables of simulation and summary statistics
• CSV output files of simulation summary and statistics summary
• 3D visualisation of grid search parameters - contours and surfaces

It is important to make the effort to understand the dynamics of your catchment, and to analyse the accuracy of your gauged data, prior to building your model. Otherwise you may develop a model with a good mathematical fit which does not capture the real hydrological processes. The accuracy of the data supplied to a rainfall-runoff model is arguably the biggest determining factor in the accuracy of the predicted streamflow. The most important of these inputs is the rainfall. The uncertainty in the rainfall timeseries depends on the errors in the point rainfall data available for gauges in the area, as well as the spatial and temporal variability in the rainfall distribution. Another key factor to be considered is the range of stage height for which rating data is available. Generally, high peaks are estimated through extrapolation of the rating curve, and as a result there is considerable uncertainty in the estimated flow volume.

In calibrating a rainfall-runoff model, attention should be paid to:

• selection of calibration period (should cover a sufficient range in climate variability)
• a coarse grid search should be employed initially to explore model behaviour - this can be refined later to potentially improve the fit
• the objective function should reflect the purpose of the application. A range of functions have been included in the software.

This version of IHACRES has been tested and scrutinised over the past six months by a team of beta testers who have extensive experience with the original version of IHACRES. These testers are identified and acknowledged in the User Guide.