Why does water in areas where Igneous rocks makeup the catchment have lower values for Total Dissolved Solids?
Total dissolved solids means stuff like salt and things that have dissolved in rivers and streams. Sedimentary rocks are like limestone and sandstone and during erosion they let go of alot of stuff like calcium carbonate which winds up dissolved in the river. Igneous rocks like granite or basalt dissolve very slowly even when eroded and therfore are not dissolved in the stream, but settle to the bottom and form new sedimentary rocks.
