WATER BALANCE

International Water Association Water Balance

The following are definitions of principal components of IWA water balance.
• System Input Volume is the annual volume put into the part of a water supply system that relates to
water balance calculation.
• Authorized Consumption is the annual volume of metered and/or non-metered water taken by
registered customers, water suppliers, and others who are implicitly or explicitly authorized to do so
for residential, commercial, and industrial purposes. It includes water that is exported.
• Water Losses can be identified by calculating the difference between system input volume and
authorized consumption. They consist of apparent losses and real losses.
• Apparent Losses result from unauthorized consumption and all types of inaccuracies associated
with metering.
• Real Losses result from losses at mains, service reservoirs, and service connections (up to the
point of customer metering). The annual volume lost through all types of leaks, bursts, and overflows
depends on their individual frequencies, flow rates, and duration.
• Non-Revenue Water is the difference between system input volume and billed authorized
consumption, and it consists of the following:
• Unbilled Authorized Consumption (usually a minor component of water balance),
• Apparent Losses, and
• Real Losses.