ISO/TS 24593:2026

Technical
Specification
ISO/TS 24593
First edition
Establishment of a master plan for
2026-04
water supply — Evaluation of water
demand
Élaboration d'un plan directeur pour l'alimentation en eau —
Évaluation de la demande en eau
Reference number
© ISO 2026
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Steps of the master plan for water supply . 2
5 Water system diagram. 3
6 Water balance . 4
6.1 General .4
6.2 Water demand .4
6.2.1 General .4
6.2.2 Current demand .4
6.2.3 Demand forecast . .4
6.2.4 Water loss situation .6
6.3 Water supply resources .6
6.3.1 Current resources .6
6.3.2 Future resources .7
6.3.3 Quality impact of resources .7
6.4 Results of water balance .8
7 Emergency supply . 9
8 Digitalisation of infrastructure . 10
9 Recommendations for optimization .11
Bibliography .13

iii
Foreword
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iv
Introduction
The purpose of this document is to define a methodology to evaluate water demand in the context of
influencing factors such as climate change and other structural alterations. The water demand is a key input
to develop a masterplan for water supply, consisting in a long-term planning document providing overall
guidance for future growth and development.
Changing conditions due to climate change, such as warmer temperatures, drought periods or the decrease
of groundwater, are important factors for water supply and demand. On the one hand these changes lead
to a scarcity in water resources, on the other hand more water demand is expected. The rise in demand
in households is accompanied by rising demands in agriculture for irrigation or industries for process and
cooling water.
v
Technical Specification ISO/TS 24593:2026(en)
Establishment of a master plan for water supply — Evaluation
of water demand
1 Scope
This document provides a methodology to evaluate the water demand to develop a master plan for water
supply. This document establishes general principles to consider relevant data of existing and future
systems in the context of climate change and other structural factors, such as social behaviour and urban or
industrial developments. It reviews the following:
— description of the water supply system;
— water balance regarding resources and demand;
— change of resource and demand in future (e.g. impact of climate change);
— water loss situation;
— maximum peak factors in present and future;
— emergency supply;
— conditions of infrastructure;
— digitalisation of infrastructure;
— recommendation for optimization.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 24513, Service activities relating to drinking water supply, wastewater and stormwater systems —
Vocabulary
ISO 24528, Service activities relating to drinking water supply, wastewater and stormwater systems — Guideline
for a water loss investigation of drinking water distribution networks
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 24528, ISO 24513 and the following
apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/

3.1
water demand
Q
dm
(estimated) quantity of water required per time unit
Note 1 to entry: This document uses the terms for water demand (Q ) for current (Q ) and future (Q )
dm dm,current dm,future
situations as an average amount per day to determine surpluses or deficits for water supply systems, as well as the
demand of certain groups such as industrial or agricultural consumers.
3.2
water supply
(estimated) quantity of water available or provided per time unit
3.3
water loss
difference between water supplied and authorized use, consisting of real water loss and apparent water loss
3.4
future peak factor
f
peak
ratio between peak demand and average demand in the same period of time
3.5
impact factor for climate change
f
climate
fixed factor used to consider the impact of climate change on water demand in the future
4 Steps of the master plan for water supply
The working methods and technologies applied for creating a master plan for water supply are:
— description of the water supply system;
— creating a water system diagram;
— examining current demand;
— analysing current resource capacity of groundwater, springs, surface water and water supply contracts;
— changing resource and demand in future (e.g. impact of climate change, population);
— calculating maximum peak factors in present and future;
— calculating water balance regarding resources and demand (mean and peak situation);
— considering water loss situation;
— analysing emergency supply;
— conditions of infrastructure;
— digitalisation of infrastructure;
— recommendation for optimization.

5 Water system diagram
In a first step, a schematic description of the drinking water system shall be used for visualization. For the
main issues water balance, emergency supply, and further recommendations, the following aspects should
be described:
a) System input and resources are:
— delivery point (external system);
— wells (well fields);
— springs;
— waterworks (as sum of water resources or water treatment capacity).
For description of system input and resources choose a logical position, name, and uniform symbol for type
and space for quantity of resource (see 6.3).
b) For supply areas:
— choose a logical supply area, which is supplied in one hydraulically connected water system.
For description of supply areas choose a logical position, name, and uniform symbol for type and space for
quantity of demand (see 6.3).
c) For connection pipes:
— describe all pipes between system input and supply areas (maximum capacity);
— describe relevant connection pipes for emergency supply.
An example of a water system diagram is shown in Figure 1 for an exemplary city.
Key
municipality long-distance water supply
wells pipe
springs border country/city
SOURCE: Reference [3], reproduced with permission of the authors.
Figure 1 — Example for water system diagram and legend declaration

6 Water balance
6.1 General
To analyse the deficit or surplus of water resources, the calculation of water balance is implemented. For this,
the total amount of water supply is balanced by the total amount of demand in different scenarios. Thereby
the total demand includes sold demand as well as water los
...