The snow melt derived rivers in the Snowy Mountains typically have the lowest average stream flow in the months from November to June, with October having the largest monthly flows of the year, e.g., mean monthly flow for October at Dalgety was prior to the Snowy Scheme. The large flows in September and October are derived from snowmelt and hydrologically it is one of the key aspects that defines these mountain waterways. Typically, Australian rivers can be defined as having highly variable river flows, with frequent zero flows even in humid areas due to the extreme age of soils and consequent extremely high water absorption to absorb minimal phosphorus via proteoid and similar root types. The mixed snow melt-rainfall rivers of the Snowy Mountains can be defined by strong seasonal patterns and remain permanent throughout the year, with no record of zero flow ever observed in the Lower Snowy. Prolonged base flows over the summer months are another feature of these types of rivers, driven by snowmelt derived groundwater.