ISO/DTS 24593

ISO TS /DTS 24593:2025-05(E)
ISO/TC 244/WG 6 224
Secretariat: AFNOR
Date: 2025-05-0111-21
Establishment of a master plan for water supply – — Evaluation of
water demand
DTS stage
Warning for WDs and CDs
This document is not an ISO International Standard. It is distributed for review and comment. It is subject to change
without notice and may not be referred to as an International Standard.
Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which
they are aware and to provide supporting documentation.

Élaboration d'un plan directeur pour l'alimentation en eau — Évaluation de la demande en eau
ISO #####-#:####(X/DTS 24593:(en)
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication
may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying,
or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO
at the address below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: + 41 22 749 01 11
EmailE-mail: copyright@iso.org
Website: www.iso.orgwww.iso.org
Published in Switzerland
© ISO #### 2025 – All rights reserved
ii
ISO TS /DTS 24593:2025-05(E:(en)
Contents
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 . 5
6.3 Water supply resources . 8
6.4 Results of water balance . 10
7 Emergency supply . 12
8 Digitalisation of infrastructure . 13
9 Recommendations for optimization . 14
Bibliography . 16

iii
ISO #####-#:####(X/DTS 24593:(en)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types of
ISO documents should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent rights
in respect thereof. As of the date of publication of this document, ISO [had/had not] received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that this
may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO'sISO’s adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 224, Drinking water, wastewater and
stormwater systems and services.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
© ISO #### 2025 – All rights reserved
iv
ISO TS /DTS 24593:2025-05(E:(en)
Introduction
The purpose of this document is the definition ofto define a methodology to evaluate water demand in the
context of influencing factors likesuch 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
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, likesuch 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 optimisationoptimization.
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 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 3.2
water supply
(estimated) quantity of water available or provided per time unit
3.3 3.3
water loss
difference between water supplied and authorized use, consisting of real water loss and apparent water loss
3.4 3.4
future peak factor
f
peak
ratio between peak demand and average demand in the same period of time
3.5 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 optimisation. optimization.
© ISO #### 2025 – All rights reserved
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 1Figure 1 for the city “Bad Wimpfen”.
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 (source [3])
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 losses, which occur in the technical facilities of
extraction, treatment, storage, or supply system.
The different calculation scenarios are:
— mean and peak scenario, ;
— current and future scenario.
Storage capacities can be considered or not when calculating water balance.
© ISO #### 2025 – All rights reserved
6.2 Water demand
6.2.1 General
To define the current and future water demand, the historical water consumption should be analysed.
Therefore, data ofon water consumption and on population, agricultural and industrial development are
useful. The total demand can also result from additional estimations, based on established targets for domestic
[e.g literslitres per capita and day (lpcd)] and non-domestic (e.g. numbers of beds within hospitals) users or
benchmarks of other systems.
For both scenarios current and future, a scenarios, mean and peak demand should be defined.
6.2.2 Current demand
To calculate the current demand, the water demand of the last years is analysed.
The current demand (Q ) is defined as a mean demand of the last years, including the sold amount of
dm,current
water (Q ) and water losses (Q ) as well as technical demand for water treatment and other processes
sold loss
within the system. The time horizon should be at least the last 5 years.
Formula (1)Formula (1) shows an example from a master plan to calculate current mean consumption:
𝑄𝑄 =𝑄𝑄 +𝑄𝑄 𝑄𝑄 =𝑄𝑄 +𝑄𝑄 (1)
dm,current sold loss dm,current sold
...