Water Balance is defined as  a method for the control of technical and financial records and documentation, which goal is to check their accuracy.   Water Balance is used in order to perform control and analysis of water supply and distribution system from the source, through pumping stations, filter stations, all pipeline types and profiles, to the customer.   

International Water Association (IWA) and the American Water Works Association (AWWA) have jointly developed a methodology for the elaboration and definition of the audit.

IWA / AWWA's Water Audit methodology is effective because it defines a series of main types of consumption and losses faced by water utilities.  It also includes a set of rational indicators used for the definition of specific attributes for the evaluation of the system, such as average pressure in the system, total length of pipelines and alike.   

All data is entered for a predefined time interval.  Water balance components based on the recommendations of IWA/AWWA are presented in the following table.

Methodology described represents a basic Water Balance and every following analysis shall be based on it. 

 There are generally two approaches to Water Balance calculation:

•  "Top - Down" and
• "Bottom - Up"

 "Top-down„ approach is a faster, cheaper and simpler, but less accurate, unlike the approach of "bottom-up" which is based on hydraulic measurement, which is more expensive, more complex and more precise.