Hydrological Drought across Peninsular Malaysia: Implication of Drought Index

Abstract

Abstract. Drought is considered a damaging natural disaster causing significant economic, social, and environmental impacts. The challenge of drought is to determine the characteristics of drought, its frequency, duration, and severity, which are critical for controlling the effects of drought and mitigation strategies. The objective of this study is to identify the drought characteristics and temporal assessment of drought using Streamflow Drought Index (SDI) and theory of runs (ToR). It also highlights the need and methods for selecting the most appropriate time scale for drought assessment, especially in tropical countries. Malaysia experiences tropical weather and monsoon seasons throughout the year with typically humid temperatures ranging from 20 °C to 30 °C. The different spatial patterns of SDI for three-, six-, nine-, and 12-month were adopted throughout Peninsular Malaysia, using 40 years of daily streamflow data from 42 gauging stations. The area under drought stress at different time scales during the study period is stable and accounts for about 24 % of the total area. The years 1997–1999, 2002 and 2016–2018 mark the most critical drought years, when more than 48 % of the total area of the basin was affected by hydrological drought. Spatial evaluation of drought characteristics shows that short-term droughts are common in most regions, with relatively high severity and frequency in the northeast and southeast of Peninsular Malaysia, where the maximum frequency reached 35.7 % and 42.8 %, respectively. The shortest scale (3-month) recorded more mild and moderate events. Since the most extensive time scale (12-month) includes more dry and wet periods, its high value may lead to misleading information for the early warning system. Using the results of this multi-scale SDI analysis, hydrologists, water managers, and policy makers can better understand the time scale selected for hydrological drought analysis. Short-term drought conditions show high interannual variability with the predominant pattern. It was shown that among the SDI time scales, the SDI for 3-month is the most suitable for effectively tracking hydrological droughts in tropical regions.