Regional low flow frequency distribution in Jiroft area by L-moments

Annual low flows are defined as the lowest average flows for consecutive days such as 7, 15,30 and 60 days (or d-days) period; in which d-days low flows are the minimum d-day movingaverage for a year. L-moment method was used for obtaining regional low flow frequencyanalysis in Halilrud, Jiroft. The stations in the area were found to be homogeneous by using two different homogeneity tests of Hosking and Wallis methods. Using goodness-of-fit-test, the best on site flow frequency distribution was found. Then for 3-parameter distributions was calculated from ZDIST period using a FORTRAN program. Pearson type III distribution was found to be the best regional low flow distribution. Finally, it was shown that catchments area is the best parameter for estimating low flows at different return periods for ungauged watersheds.