Dumai City is the result of the expansion of Bengkalis Regency which was inaugurated as Dumai City on April 20 1999, with Law no. 16 of 1999 dated April 20 1999 after previously being an administrative city (kotif) within Bengkalis Regency. Dumai City experiences extreme seasonal variations in monthly rainfall. In the field of water resources analysis, rainfall data is one of the important data…