MODELING SPATIAL VARIABILITY OF RAINFALL OVER A CATCHMENT

Simulation of catchment processes that influence the quantity and quality of storm water runoff are employed in many circumstances where it is proposed to modify the existing catchment management practices and it is infeasible to trial physically the proposed management practice. An essential and necessary component of any catchment simulation is the model whereby the rainfall over the catchment is estimated. Most of these models, such as Thiessen polygons, were developed prior to the development of the digital computer and the subsequent development of hydroinformatic tools. Presented here are the results of a study investigating the accuracy and reliability of hydroinformatic tools for modeling the spatial and temporal distribution of rainfall over a catchment. It was found that using spline surfaces within a geographic information system (GIS) produced robust and accurate estimates of rainfall and enabled real-time estimation of spatially distributed patterns. Furthermore, use of the GIS enabled estimation of alternative hyetographs for different locations within the catchment.