Author(s): Sasin Jirasirirak; Aksara Putthividhya; Somkiat Prajamwong; Wimolpat Bumbudsanpharoke Kamkanya

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Keywords: Drought index; Drought early warning; EEC Thailand

Abstract: Thailand is facing increasing water risks as a growing population, economic growth and the looming threats posed by climate change are expected to make sustainable water management and water security significantly more difficult. The government thus needs to move from a crisis response to a risk-management approach by maintaining acceptable levels of risk in 4 main areas including (1) drought risk; (2) flood risk; (3) the risk of inadequate water quality (water pollution); and (4) the risks of undermining the resilience of freshwater systems (water use and water allocation). This paper aims to enhance and facilitate the move to a risk-based approach to water security by making better use of drought analysis instruments using appropriate indices/indicators to reduce water shortages in drought-stricken areas especially under prolonged weather events hopefully to formulate water policies for justified spatio-temporal water allocation and access in the Eastern Economic Corridor (EEC) region. Long-term analysis of meteorological and hydrological drought indices is conducted to characterize and monitor drought trends in EEC using the Standardized Precipitation Index (SPI), the Standardized Precipitation Evapotranspiration Index (SPEI), and the Streamflow Drought Index (SDI). Computed time series of the 3 selected indices are compared with observed drought events by assimilating the weekly rainfall and monthly streamflow and evapotranspiration (PET) data from ground observations and remotely-sensed Earth observing satellites (i. e., MODIS, Aqua MODIS, TRMM, and GPM) data and climate drought indices are calculated. The performances of 3 climatic indices seem to be able to capture the main characteristics of drought conditions in EEC region and the indices also designate extreme drought frequency and severity since early 2000s. The 2 indices obviously can also detect notable drought episodes during year 1997-98,2003-04, and 2015-16 consistent with El Nino years. The overstating the frequency of droughts at the 1-month timescale by SPEI and SDI still exists just like the case of SPI. SPEI indicated substantial higher severity and longer duration of drought events compared to those of SPI especially for the year 1991-92 drought episode, while SPI under-quantified the magnitude and missed to represent extreme droughts during that period. SPI climatic indices shows diverse effects on drought conditions under the prolonged records with certain restrictions, while multivariate index (i. e., SPEI) illustrates the obvious advantage of temporal variation of drought frequency, magnitude, and severity characteristics detection. The better performance of SPEI indices compared to SPI emphasizes that PET plays an important role in hydrologic cycle in Thailand with tropical monsoon weather system and its variation is primarily affected by precipitation as well as land use and land coverage change. Development of multiple drought indices demonstrated in this study can be beneficial for drought assessment, early warning, and future projections for planning and support the implementation of preventive measures or mitigation of drought impacts.

DOI: https://doi.org/10.3850/978-90-833476-1-5_iahr40wc-p0600-cd

Year: 2023