Aquifers earmarked for drinking water between Geraldton and Busselton could be compromised if companies are allowed to drill for gas through them, the Water Corporation has warned.
The State-owned utility also raised questions about why hydraulic fracturing, or fracking, would be permitted in protected water areas when providing drinking supplies was of "paramount importance".
The comments came at an Upper House parliamentary inquiry investigating the implications of fracking in WA.
The corporation said the economic upsides of fracking, which unlocks unconventional gas resources such as tight and shale gas, could be "significant".
But it warned the chemicals used could contaminate ground and surface water supplies if handled incorrectly.
It suggested fracking should be banned in protected water catchments, which were less than one per cent of the land that could be developed for fracking.
The corporation and the Department of Water also want a 1.5km buffer from fracking around water catchments as an added protection.
Asked by inquiry member and Labor MP Stephen Dawson which drinking water sources were particularly at risk, the corporation identified several areas in the Kimberley and Gascoyne.
The corporation's general manager of planning and capability Ashley Vincent suggested aquifers under the coastal strip between the South West and Geraldton could also be susceptible.
"The actual areas of overlap (where there are protected water catchments and potential unconventional gas developments) are very small," Mr Vincent said.
"But recognising that they are significant sources that supply the metropolitan scheme, it is important that they are recognised and protected is our view."
The oil and gas industry has acknowledged the importance of drinking water supplies but has argued that source protection and fracking are not necessarily incompatible.