River-water

In such a process the dammed up river-water passes over cascades (for aeration) into gravel pre-filters, is collected at the end of said filters and, after repeated aeration, brought onto sand filters.

Source: wiktionary

The presence of widespread lateritic formations has been thought to indicate very high rates of silica removal in tropical environments, G.V. Bogomolov et al. (1966) asserting that the silica content of tropical river-waters is greater than that of open streams in higher latitudes, and N.M. Strakhov (1967) noting that the migrational capacity of SiO₂ is particularly high in the humid tropics.

Source: wiktionary

She spit out a mouthful of sand that tasted like Grape Nuts soaked in river-water.

Source: wiktionary