Average rainfall entering the dam in the period 1912 to 2000 was 28.8 gigalitres (1.02 billion cubic feet) per year, however, reduced rainfall has resulted in a 35% decrease since 1975 to 18.7 gigalitres (0.66 billion cubic feet) per year.

[4][5][6] The dam forms part of the Archaean Yilgarn block, consisting of mainly granitoid rock with dolerite dykes and is capped with laterite.

According to a Water Corporation study shown in the table below, the dam contains low levels of metals and inorganics, and the only pesticide present is simazine, present in only one sample in levels well below Australian Drinking Water Guidelines.

A 2005 protection plan also by the Department of Environment showed there are risks of pathogen contamination, turbidity, pesticides and nutrient contamination, with pathogens being the most severe possibility, but turbidity being the one with the highest possibility of occurring.

[7] There was controversy in mid-2015 after a group of local farmers backed by former-cop Liberal MP Murray Cowper claimed the North Dandalup River was being "killed" by the Western Australian Department of Water by not releasing water from dams, including the North Dandalup dam into the river to increase flow.