Derivation of Depth- Area- Duration Curves for Estimating Areal Probable Maximum Precipitation in Fars Province

Probable Maximum Precipitation is the greatest depth of precipitation for certain duration. This study aimed derivation of Depth-Area-Duration (DAD) curves in Fars province for estimating 24-h Probable Maximum Precipitation (PMP24) using two Hershfield statistical approaches and estimating the suitable frequency factor (km). For these purposes the maximum 24-hour precipitation data ((P24)max) with a period of 12-61 years were obtained for 52 stations with long-term data. The km values in the first and second approaches were estimated between 15.3 to 18.4 and 1.6 to 6.8, respectively. Also the corresponding PMP24 were between 280 to 850 and 112 to 380 mm respectively for the two approaches. The PMP24 values were estimated of 50 and 100 year return periods 714 and 771 mm, respectively. Results showed that the km values for the second approach are 75% lower than the km for the first approach. The ratios of PMP24 to (P24)max were obtained in the range of 2.6 to 7.4 and 1.4 to 2.7 respectively for the first and second approaches. Therefore, the second approach is more reliable. Also, the isohyet maps were drawn for PMP for the two approaches over the study area using DEM in GIS. DAD and area reduction curves were determined for each approach. Using these curves it is possible to convert point PMP24 values to areal values in the Fars province.