The Upper Gulf,
where this work was performed, has an inverted Ushape
and is the catchment basin of four large rivers
on the northern side (Maeklong, Thachin, Chao
Phraya and Bangpakong Rivers) and two on the
western coast. Among them, the Chao Phraya River
has the greatest discharge (55-year average
¼ 482m3/s) into the Upper Gulf while the Mekong
River (average flow ¼ 15 000m3/s) has the largest
flow in the region, discharging into the South China
Sea with some influence on the lower Gulf