Rainfall data, an essential element of storm water management analyses, is recorded at and collected from rain gauges. Therefore, the location of the rain gauge is important. The closer the rain gauge is to the flow meter the better. However, this may not always be possible. Also, rainfall data obtained and used for modeling from adjacent/closest rain gauge does not, in most cases, best represent the sub-catchments. Often modellers must use rain gauge data that are not truly representative of the area where the flow is being recorded. The best rainfall data are recorded at the center of each sub-catchment, as they capture the true influence of rain on that particular sub-catchment. In order to overcome this, the Distributed Rain Modeling Technique or DRMT was introduced. DRMT uses math interpolation on each actual live rain gauge and interpolate the values of intensity at each time step to create a virtual rain gauge. The DRMT takes data from multiple rain gauges, surrounding a site of interest or focus, and interpolates to create rainfall ‘surfaces’ for each modeling time step at the centroid of each catchment’s tributary area. This approach is helpful to account for temporal and spatial variability of storm events over a relatively large drainage area and to interpret the observed flow and level data. The interpolation technique currently used is has two options: IDW and Spline Interpolation based on TatukGIS method.

The DRMT tool is useful to calibrate models covering large areas with multiple rain gauges. The simulated hydrographs are more reasonable compared to the one without using DRMT.