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Annual Mekong Hydrology, Flood and Drought Report 2018

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Mekong River Commission
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This is the first Annual Mekong Hydrology, Flood, and Drought Report (AMHR). After 13 years, starting in 2005, the Annual Mekong Flood Report (AMFR) is replaced by this new format.

In 2019, the Joint Committee – the MRC’s governing body – decided to integrate drought monitoring and management functions into the Regional Flood Management and Mitigation Centre (RFMMC) and to rename the RFMMC to the Regional Flood and Drought Management Centre (RFDMC). Taking the vulnerability of the basin to more extreme weather events into account, the need to address flood and drought in an integrated way is logical.

In the wake of the structural change, the new RFDMC introduced new approaches and embarked upon assessing drought conditions by means of drought indices. The scope of information that is now published by the MRC on its website covers not only flood data and forecasts but also drought-relevant information. The AMHR builds on these new assessments.

The high variability of climate and resulting conditions that occur from year to year, but also intra-annually, calls for an integrated approach. 2018 is a good example with extreme rainfall in July and August followed by rather dry conditions with distinct below average soil moisture as of September in the lower half of the Lower Mekong Basin (LMB). Generally marked as a wet year, the last quarter of 2018, however, was the beginning of an exceptionally dry period that fully developed in 2019.

This and subsequent AMHRs will cover and combine different hydrological subjects (i.e. flood, hydrology, drought recognition, monitoring and early warning, remote sensing, modelling, and water management) to provide an annual summary of the previous year and to enhance knowledge and awareness. This first edition introduces these topics in Section 2 and provides a combined analysis of flood and drought in Section 3. Those familiar with the AMFRs will still find the known and well-established evaluations and graphs related to rainfall maps, water level and streamflow hydrographs, flood volumes, etc., as well as the section with the country reports. In addition, as with the previous annual flood reports, the AMHR will include a specific theme. Since the frame of the AMHR is wider in scope, the themes will be more diversified.

In the new format, the LMB is subdivided into six regions in accordance and similar to the segmentation used in the Council Study. The Council Study is the comprehensive state-of-the-art, integrated, cross-sectoral report on sustainable management and development of the Mekong River generated by the MRC (MRC, 2018b). If possible, analyses were performed so as to address these regions separately.

The year 2018, however, brought about a negative headline, too: the dam break of XePian Xe-Namnoy Dam in Lao PDR. This incident is described in the report.

Taking expected impacts of climate change, development in the LMB, and enhancement of advanced hydrological techniques into consideration, the new format is necessary to inform and update on the complex hydrology of the LMB and its socioeconomic implications from year to year.