Ha D. T., Ouillon Sylvain, Vinh G. V. (2018). Water and suspended sediment budgets in the Lower Mekong from high-frequency measurements (2009-2016). Water, 10 (7), art. 846 [24 p.]. ISSN 2073-4441.
Titre du document
Water and suspended sediment budgets in the Lower Mekong from high-frequency measurements (2009-2016)
Based on a new dataset of high temporal resolution of water discharge (hourly frequency) and suspended sediment concentration (twice daily frequency at ebb and flood tides) at Can Tho and My Thuan stations during the 2009-2016 period, monthly and annual flow and suspended sediment flux of the lower Mekong River were calculated. The present water discharge of the Mekong River to the sea can be estimated to be 400 km(3) yr(-1), +/- 100 km(3) yr(-1) depending on El Nino Southern Oscillation (ENSO), and the present sediment supply to the sea can be estimated to be 40 Mt yr(-1), +/- 20 Mt yr(-1) depending on ENSO. The ENSO influence (proxied by the Southern Oscillation Index-SOI) on Q (water discharge) and Qs (sediment flux) is at maximum at a time lag of 8-9 months. The 2010-2011 La Nina event increased the water supply by almost 30% and the sediment supply by 55% in 2011. The 2015-2016 El Nino event decreased the water supply by 20% and the sediment supply by 50% in 2015-2016. The average net water discharge was 12,550 m(3) s(-1) in neutral years. The Tien River at My Thuan accounted for similar to 52%, and the Hau River at Can Tho for similar to 48% of the total Mekong River discharge, with small variations (of the order 1%) amongst years. In terms of suspended sediment delivery to the sea, the Tien River accounted for a more variable portion of 55% in neutral years, 57.3% in 2015-2016 (El Nino) and 62% in 2011 (La Nina). 80% of water discharge occurred during the flood season (July-December) and 20% occurred in the low flow season (January-June), the proportion being 91% and 9% for the sediment supply. Previous estimates of annual sediment supplies to the sea (145-160 Mt yr(-1)) had been established before 2003. Possible origins of the recent reduction by similar to 75% of sediment supply are presented and discussed.
