Water Discharge and Total Suspended Sediment Data
We generated daily water discharges at the three sites using rating
curves and water level data provided by the Cambodian Ministry of Water
Resources and Meteorology (MOWRAM) for the period 1993 to 2018. We
obtained sediment data from MOWRAM under the Mekong River Commission
framework: Water Quality Monitoring Network (WQMN). Total suspended
sediment (TSS) concentration was obtained from the water quality
sampling conducted on a monthly basis by MOWRAM from 1995 to 2018 at
Kratie station and 1993 to 2017 at Chroy Changvar station. For Tonle Sap
River, the monthly basis water sampling (once every month) also carried
out from 1995 to 2018. Table 1 summarizes the data (TSS and
water discharge) coverage period and number of sampling used in this
study. In WQMN database, the TSS samples were collected at 0.3 m below
the water surface in the middle of the mainstem cross-section at each
station. The samples were at the designated laboratories by MRC and
recommended analytical method for TSS analysis (2540-D-TSS-SM) (Kongmeng
& Larsen, 2016). The reader should bear in mind that these were not
depth-integrated samples, but single, near-surface samples from the
approximate mid-point of the river. To the extent that the suspended
sediments in the river are well-mixed, the samples may be representative
of true loads, but if concentrations are heterogeneous in the vertical
columns or across the channel, the measured TSS may not be
representative of the average sediment concentration channel-wide, and
may under-represent suspended sand especially, as sand concentrations
would tend to greater near the bed. Note that since we analyzed flow and
sediment records based on the hydrological year, our period of record
analysed (by hydrological year) is one year shorter than period of
available data expressed in calendar years (i.e. if the calendar year is
1995-2018, thus the study expressed as hydrological year 1995-2017).
Table 1 : Data coverage period and the number of Total suspended
sediment (TSS) sampling and water discharge data used in the study.