The effects of forecasted precipitation amount on probable maximum precipitation and probable maximum flood parameters

Abstract

This study aims to calculate the probable maximum precipitation (PMP) and probable maximum flood (PMF)parameters. For this purpose, data length adequacy of historical precipitation data and data forecasted were analysed using the Long Ashton Research Station Weather Generator under Representative concentration pathway 8.5 and 4.5 scenarios in 2021-2040. Modified method and the method provided by soil conservation service-curve number were used to estimate (PMP) and (PMF)parameters, respectively. To investigate data adequacy, the Hurst coefficient was examined for Shiraz, Abadeh and Lar according to the length of statistical periods. Shiraz, Abadeh and Lar have the desired data with the coefficients of Hurst 0.61, 0.57 and 0.52, respectively. The results indicate increased precipitation under both Representative concentration pathway 4.5 and 8.5 scenarios in 2021-2040 for all three climate zones compared to historical data. (PMP) parameter has experienced an increasing trend in Abadeh and Lar and a decreasing trend in Shiraz due to a decrease in the value of 24hour (PMP) parameter under both scenarios compared to historical data. Given the (PMP) parameters for Shiraz region, the (PMF)parameter has experienced a downward trend under both scenarios and an upward trend for Lar and Abadeh compared to historical data.