Most of the forest within reasonable distance of Perth city, and suitably accessible for bushwalking, also lies within drinking water catchments. Bushwalkers recognise the need to protect drinking water quality. Restrictive regulations surrounding traditional bushwalking activity in water catchments in Western Australia however appear to be based upon reducing the risk faced by managers of the catchments, rather than on any real risk of adverse effects on drinking water quality. 

The Department of Water issued "Operational Policy 13: Recreation within public drinking water source areas on Crown land"  in 2012. The Policy largely maintains DoW's previous position that bushwalking is not permitted within 'reservoir protection zones' (RPZ’s). Certain restrictions also apply to recreation activities, including bushwalking, within the outer catchments.

Lake CYOConnor

Previous DoW recommendations published in 2007 if not eventually reversed in line with the newer Policy 13 would in effect bar walking (as an “unacceptable activity”) within most traditional bushwalking areas within the Perth region other than along the Bibbulmun Track. Meanwhile widespread State forestry and bauxite mining operations continue across those same catchments that were considered by DoW and some conservation groups to be inappropriate for low impact, off-track bushwalking.

Catchment operations managers informally recognise that the risk to water quality posed by traditional bushwalking activity is negligible. Also, Perth's dependence upon the Hills catchments and reservoirs to source drinking water has substantially declined over recent years. Despite this, policy managers have adopted an attitude that although the risk is negligible, it is still a risk and any activity that may be a risk is to be avoided as a 'precautionary' measure.

Internationally-respected applications of the “precautionary principle” recognise that a zero risk objective is unrealistic and unsustainable. Desired levels of water catchment protection should be rational, not disproportionate to actual or perceived risks to water quality.