Hourly Disaggregation of Daily Rainfall in Texas Using Measured Hourly Precipitation at Other Locations

Abstract

A method to disaggregate daily rainfall into hourly precipitation is evaluated across Texas. Based on measured precipitation data, the method generates disaggregated hourly hyetographs that match measured daily totals by selecting storm intensity patterns from measured hourly databases using a one parameter selection method. The model is applied across Texas using historic data measured at hourly precipitation gauges; performance is evaluated by the model’s ability to reproduce the measured hourly rainfall statistics at each gauge. Initially, each hourly precipitation gauge is evaluated in its performance as a disaggregation database. Based on a cluster analysis of the results to determine which precipitation databases should be used for general disaggregation, no preferences in space or among gauge characteristics (e.g., period of record, precipitation statistics) were identified. As a result, a Texas state database that contains all of the measured hourly data in Texas is proposed for use by the disaggregation algorithm. The state database is verified for a selection of gauges across Texas and performed as well at a given station as using that station’s measured rainfall for the disaggregation. The method is further applied to estimate intensity-duration curves, which show that the disaggregation algorithm captures the majority of the storm intensities well and diverges by less than 17% from the measured intensities for the extreme runoff-generating events.