Development of regional synthetic unit hydrograph for Texas watersheds

This study is to develop a regional synthetic unit hydrograph (UH) for watersheds in the central Texas. A method to develop regional UH has been proposed after a comprehensive literature review and observed UHs analysis with FORTRAN programs. Optimal unit hydrographs were estimated by linear programming and least-square methods for 1635 (eventually 1812 after event separation) storm events from 90 different watersheds in the central Texas. The UHs developed were fitted with Gamma mathematical function and the Gamma parameters were computed. The individual Gamma UHs and basin average Gamma UHs were applied to other storm events in the watershed to quantify the predictability of the computed unit hydrograph. Seventeen error parameters were incorporated in the analysis and Gamma UH parameters were selected from results with optimum errors. Five different parameters defining the Gamma UH characteristics and five watershed/rainfall parameters were considered in the study for regression analysis but only two parameters were identified to correlate with the watershed parameters. Regression equations have been developed to estimate Gamma UH parameters and classified for different watershed sizes. Finally, a procedure to develop the UH using regional unit hydrograph method for central Texas watersheds has been presented.