Temporal variability in suspended-sediment dynamics within three distributaries of the Ayeyarwady Delta, Myanmar
Abstract
The Ayeyarwady River is one of the largest sources of sediment to the global ocean, discharging >108 tons annually. However, little is known about the timing, character, or routing of that sediment within the large Ayeyarwady Delta, which is building into the northern Andaman Sea. Within its delta, the Ayeyarwady River divides into numerous distributary channels. We present data collected in three distributary channels: the western Pathein River, the central Bogale River, and the eastern Yangon River. This study examines how the suspended loads of these distributaries vary spatially (along and between distributaries) and temporally (decennially, seasonally, fortnightly) using in-situ and remote-sensing approaches. During the high-discharge period (July-Oct), these distributaries are largely freshwater tidal rivers, with estuarine conditions displaced seaward near the river mouths. However, during low-discharge conditions (Dec-May), salinity extends many tens of kilometers upstream of the river mouths, creating estuarine conditions within the river channels. In addition to seasonal variability across all distributaries, there is significant spatial variability between distributaries associated with increased tidal range toward the east, from mesotidal conditions at the mouths of the Pathein and Bogale Rivers, to macrotidal conditions at the mouth of the Yangon River. During high-discharge conditions, suspended-sediment concentrations (SSC) and sediment dynamics are similar across all three distributary channels. However, with the onset of estuarine conditions during the low-discharge period, SSC values are observed to decrease in the Pathein River (10s mg/L), while in the Yangon River, SSC increases to values exceeding 5 g/L. In addition to in-situ data collected during the two seasonal conditions, we present estimates of surface SSC derived from calibrated multispectral remote-sensing products. These data provide a synoptic view of turbidity across the delta, capture the transitions between high- and low-discharge conditions, and resolve long-term trends in surface SSC for the distributaries of the Ayeyarwady River. These new observations help constrain the sediment-discharge behavior of one of the world's largest and least-understood rivers.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMEP13C2113F
- Keywords:
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- 1051 Sedimentary geochemistry;
- GEOCHEMISTRYDE: 1165 Sedimentary geochronology;
- GEOCHRONOLOGYDE: 9320 Asia;
- GEOGRAPHIC LOCATIONDE: 3022 Marine sediments: processes and transport;
- MARINE GEOLOGY AND GEOPHYSICS