Water Supply


Households in general

General disaster preparedness for households should include the storage of at least three days' supply of clean drinking water.

Roof catchment water supplies

For roof catchment rainwater systems, we advise disconnecting the downpipe from the roof to the tank prior to the ashfall. Tank water contaminated with ash is unlikely to be a health hazard, but will probably have an unpleasant metallic taste, so it may be necessary to empty, clean and refill the tank.

Water Treatment Plants

How to Prepare

Operational plans should be developed well in advance for infrastructure at risk from volcanic ashfall.
  • Coordinate plans with emergency management groups, scientists, and infrastructure providers.
  • For plants at risk from ashfall, strategies to reduce vulnerability to ashfall include: installing automatic shutdown of intakes based on a turbidity threshold; covering open-air sand filters; and increasing treated water storage volume.
  • Anticipate increased maintenance schedule; review stocks of essential items.
  • Ensure access to back-up power generation.

How to Respond

Take precautions to exclude ash from treatment plants:
  • Close intake before turbidity levels become excessive.
  • If necessary, adjust coagulant dosage to attempt to achieve satisfactory turbidity reduction.
  • Consider installing temporary covers such as tarpaulins over open-air sand filters.
  • Protect other exposed equipment such as electrical control panels and pumps.
  • Ensure that staff working outdoors are supplied with adequate personal protective equipment (longsleeved clothing, heavy footwear, fitted goggles and properly-fitted P2, N95 or FFP2 dust masks). Masks should be changed when clogged.
  • If industry-certified masks are not available, other masks may provide partial protection. For more information: https://www.ivhhn.org/index.php/ash-protection
  • In addition to the routine monitoring undertaken for compliance purposes, carry out more frequent checks on turbidity, pH and chlorine residuals in the distribution network. If necessary adjust chlorine dosing.
  • Anticipate increased water demand following an ashfall. Where possible, use alternative non-potable sources of water for clean-up and firefighting. Do not use recycled wastewater (e.g. treated effluent) for these purposes. Encourage clean-up using brooms and shovels (with appropriate PPE) rather than hoses. Advise the public to practice water conservation.
    • Be aware of the possibility of pH depression in low alkalinity surface water sources and adjust any pH-sensitive treatment steps as required. Remind consumers of the need to flush their taps briefly before drawing water.
  • Public anxiety about contamination of water supplies is common after a volcanic eruption. Refer concerns to the public health agency.