Abstract:
Drought problem becomes a routine thing that occurred in Indonesia, but the prevention and control of this case is very slow, so it becomes unresolved issues. The problem occurs is the lack of data indicating the level of drought in the region. Therefor, by using the rainfall data in Indragiri watershed, we can obtain an index of drought. Drought index can be used to indicate the drought in the rainfall data series such as drought duration and amount of drought by using the Run Theory. The data used are 25-years rainfall data of Air Molek, Pangkalan Kasai, Sentajo, and Talang Jerinjing Station and 15-years rainfall data of Air Molek, Pangkalan Kasai, Sentajo, Talang Jerinjing, Lirik, Sijunjung, Tembilahan, and Usul Station. The time period used are monthly, 15 daily, 10 daily, and weekly. Rainfall station experienced the highest drought duration and amount of drought for 25 years rainfall data was Air Molek Station, while the lowest was Talang Jerinjing Station. For 15 years rainfall data, the highest and the lowest drought duration for each period of time were in different stations, while the highest amount of drought was in Pangkalan Kasai Station and the lowest amount of drought was in Talang Jerinjing Station. The description of drought duration value and the amount of drought could be found with Golden Surfer 8.0 software. The description of isohyet method between using four rainfall stations and eight rainfall stations shows that the differences in contour value are not very significant.
