The turquoise colour of the lake's water is due to glacial flour suspended in the meltwater from its two primary inflows, the large Sphinx Glacier to the east and the Sentinel Glacier to the south on the flanks of Mount Garibaldi. Throughout most of the year, outflow from Garibaldi Lake occurs only via seepage through cracks in the lava dam, with Rubble Creek appearing from springs at the base of The Barrier. During spring snowmelt, outflow is sufficient for surface drainage to occur via a shallow channel across the lava flow, into Lesser Garibaldi Lake and Barrier Lake about 1.6 km (1 mi) west of the main lake's shore.