Open AccessRainfall trend and variability over Opak River basin, Yogyakarta, Indonesia
Author(s) -
Wakhidatik Nurfaida,
Hendra Ramdhani,
Takenori Shimozono,
Indri Triawati,
Muhammad Sulaiman
Publication year - 2020
Publication title -
journal of the civil engineering forum
Language(s) - English
Resource type - Journals
eISSN - 2581-1037
pISSN - 2549-5925
DOI - 10.22146/jcef.60628
Subject(s) - trend analysis , environmental science , flooding (psychology) , climate change , drainage basin , water resources , precipitation , climatology , hydrology (agriculture) , physical geography , geography , meteorology , geology , statistics , psychology , ecology , oceanography , mathematics , cartography , geotechnical engineering , psychotherapist , biology
Rainfall intensity seems to be increasing nowadays due to climate change as presented in many studies of both global and regional scale. Consequently, cities worldwide are now more vulnerable to flooding. In Indonesia, increasing frequency of floods was reported for the past decades by The National Agency for Disaster Countermeasure (BNPB). To understand the rainfall changes, long-term trend evaluation over a specific area is then crucial due to the large variability of spatial and temporal rainfall distribution. This study investigates the homogeneity and trend of rainfall data from 20 stations over the Opak River basin, Yogyakarta, Indonesia. A long-term ground observation rainfall data whose period varies from 1979 to 2019 were analyzed. Non-parametric Mann – Kendall test was applied to assess the trend, while the magnitude was calculated using the Sen’s slope estimator. An increasing annual maximum of daily rainfall intensity was observed at four stations on a 0.95 confidence level based on the Mann – Kendall test, while the Sen’s slope estimator shows a positive trend at almost all stations. The trend of heavy rainfall frequency was also found to be significantly increased, with only one station showed a decreasing trend. Furthermore, this paper also described the spatial and temporal rainfall variability. Positive trend was mostly found during the rainy season, while the negative trend occurred during the dry season. This could pose a challenge for water resource management engineering and design, such as water supply systems or reservoir management. Understanding this phenomena will benefit hydrologists in preparing future water resource engineering and management.