6. Conclusions
The Ming Yong glacier catchment in the upper Mekong basin is
characterized by distinct wet and dry seasons, with discharge and
suspended sediment concentrations (SSC) increasing from February to July
and decreasing from August to January. The yearly variations in sediment
load for Ming Yong glacier are large (44 kt in 2013 to 91 kt in 2015,
and 73 kt in 2016), despite small variations in water discharge. More
than 65% of the annual sediment load is contributed between June and
August. These observed seasonal variations in the sediment load indicate
the complex competing influences of the supply and storage of suspended
sediment load. Specifically, the clockwise hysteresis relationship
suggest that sediment is stored during the low flow season and
transported when flow increased from February to July, with the
exhaustion of sediment supply after July. Even though discharge and SSC
are generally positively correlated, seasonal variations result in
different sediment rating relationships due to the influence of glacial
meltwater. Based on the in-situ observations over three hydrological
years, the sediment yields are estimated to be 1104
t/km2/year in 2013, 2283 t/km2/year
in 2015, and 1833 t/km2/year in 2016.
This study provides baseline measurements for potential future
monitoring of the glacial catchment in response to climate change.
Concurrently, the data fills the knowledge gap in sediment data for the
headwaters of the Mekong River. As this study was conducted in-situ,
data was collected manually. For instance, the collection of water
samples for filtration or the measurements of water depth could
introduce random errors. Thus, the use of specific hydrology equipment
in subsequent studies such as data loggers or turbidity meters can
increase the sampling frequency and accuracies of future sediment load
estimates. Furthermore, installation of a nearby weather monitoring
station can give more insight into the diurnal and seasonal ablation
patterns of the Ming Yong Glacier, allowing better attribution of the
variation in its discharge or transport capacity to climatic or other
environmental factors.