Contents of Unaccounted-For Water

Unaccounted-for water is defined as the ``Water loss calculated as the difference between the quantity of water fed into a distribution system (drinking water production) and the quantity of water put to legitimate use, which has been metered or can be estimated. Quantities of water put to legitimate yet unmetered public use, e.g. for fire fighting, or distribution system rinsing, have to be estimated.

Quantities of water that are wasted by the consumers or lost through leaking fittings, as well as losses occurring between raw water extraction and input into the distribution system are not considered as unaccounted-for water. Unaccounted-for water includes both physical losses and nonphysical losses''[15] .

The term 'non-revenue water' is frequently used. It describes the quantity of water which is lost or withdrawn from the water network without being paid for.

**Figure 5:** Water Loss
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An international standardized definition of the term ``water loss'' does not exist yet. In [15] it is suggested that ``water loss and waste can be defined as the total quantity of water that is lost or put to illegitimate use during the period of its human utilization from the point of its extraction from a natural body of water [...] to the point of its intended consumption.'' In Germany water loss is fixed in the national standard DIN 4046: ``Water loss is that percentage of input that cannot be accounted for by volume and is partially lost. It comprises both physical and nonphysical losses.''

**Figure 6:** Unaccounted-For Water
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In Germany physical water loss are defined as ``that amount of water which is lost without being used due to failures and deficiencies in the distribution facilities.'' [1]. Nonphysical water loss is defined as ``that amount of water which is not registered, due to incorrect reading of the measuring instruments installed (measurement errors) and/or absent or inaccurate estimates in the absence of measuring instruments (estimation errors)'' [1].

In particular, in developing countries the rate of UFW is extremely high. The analysis of UFW rates shows the efficiency of the economic system and technical part of the water distribution network and its management.

In the following physical losses are called technical- and nonphysical losses are administrative losses. The thesis concentrates mainly on technical losses, even if the administrative part promises a more efficient loss reduction. In section 4 the current situation of the Al Koura water distribution network is described in detail.