Updated IDF Curves for Mashhad

Estimation of rainfall intensity at specified duration and return period is an essential parameter in all water projects. Drainage, watershed management, dam construction, surface run-off disposal are some examples of such projects. Airport station is the oldest station in Mashhad and is supervised by Iran Meteorological Organization. This station, as synoptic, has recording rain-gauge device since 1969. Based on 1969-1993 data, intensity-durationfrequency (IDF) of this station has been done by 2-parameter Gamma. Theother charts of this station are to 2006, were digitized and up-to-dated IDF is prepared. Gumble distribution best fitted the data. However, the results showed that, despite of decreasing trend of rainfalls, there are negligible differences between this IDF and the previous one.