Drought index analysis on the Nusantara Capital City of Indonesia (IKN)

The Indonesian Government have decided to relocate the capital city of Indonesia from DKI Jakarta to East Kalimantan Province in 2024. This new capital city of Indonesia called Nusantara Capital City (IKN) presents strategic issues regarding the lack of water availability and hydrometeorological disasters. Continuing the previous study about statistical comparison of rainfall extremes between Jakarta and IKN, this study on drought in IKN aims to investigate the water availability's condition by using drought index associated with rainfall intensity and number of no rain days. We analyze the trend of consecutive dry days (CDD), The highest one-day rainfall (RX1day), and Simple Precipitation Intensity (SDII) indices yearly and seasonally. The ground-based daily rainfall data at Sepinggan, Samarinda, Penajam Paser Utara, Balikpapan, and Sepaku during 1979-2022 (42 years) are used in this study. The Mann-Kendall method is carried out to detect the trend of each index. The preliminary results show that in general CDD shows no trend tendency over all stations. However, we found a tendency of a decrease CDD in Dec-Feb (DJF) and Sep-Oct (SON) indicating these periods have generally have no rainy days overall resulting in decreasing CDD relative to other seasons. However, the CDD tends to show a slight increase trend between 1980 and 2009. In 1997, the CDD index was exceptionally high coincided with El Nino event. In contrast, the SDII and RX1day tend to increase in Jun-Aug (JJA). This study has found that the yearly decreasing trend of CDD does not simply conclude that there is no contribution of CDD to drought events. Instead, the drought might be more related to high occurrence of CDD influenced by large scale events depending on season and topography. This research has provided basis knowledge about CDD associated with drought and should be beneficial to develop strategic plan for water availability and its impact on the forest fire mitigation management as well as reducing the hydrometeorological disasters which commonly occur over IKN and its surrounding areas.