The Squamish River is a short but very large river that has a drainage basin of 3,328 square kilometres in size. The total length of the Squamish River is approximately 80 kilometres.
About 21.8 km southwest of the source, the Squamish meets the Elaho River. The Elaho River, which is the largest tributary of the Squamish, actually has more volume than the Squamish where they join. After its confluence with the Elaho, the river moves southeast for another 24.8 km until its confluence with the Ashlu River, its second largest tributary. Another 16.4 km from there, it is met by the Cheakamus River, and 4.7 km further south, by the Mamquam River. From there, the river flows another 6 km to its mouth at the head of the Howe Sound.
The Squamish water levels can drastically rise and drop over a short period of time and is subject to flooding. The average flow is between 100 and 500 m³/s depending on season. The large flood of 2003 the river peaked at 3140 m³/s and was the largest recorded flood in over 100 years. In comparison the 1991 flood peaked at 2460 and in 1984 it was 2610. Average high water events range from 1200-1600 m³/s and this translates to about 6-7 meters for water level. For more historical or current water level data please visit Environment Canada's Water Survey of Canada.The graphs below use Environment Canada's real time hydrometric data for the Squamish River (3 hour lag time).