Submitted paper presents risk assessment using risk analysis of the rainwater harvesting system. The aim of this article is to present selected approach in risk factors identification within proposed RWH system evaluation for an experimental family house. In our case, we were able to collect helpful information from questionnaires that later facilitated the risk identification as well as risk assessment phase along with the aid of brainstorming activities within a team of experts. The results from the risk analysis were verified by the AHP and empirical multilevel comprehensive evaluation, which was also found to be useful

Kaposztasova, Daniela

Purcz, Pavol

Vranayová, Zuzana

Portal Czasopism Naukowych (E-Journals)

* Ph.D. Eng. Daniela Kaposztasova, Assoc. Prof. Ph.D. ZuzanaVranayova, RNDr. Ph.D. Pavol Purcz, 
Department of Building Services, Faculty of Civil Engineering, Technical University of Košice.
DANIELA KAPOSZTASOVA*, ZUZANA VRANAYOVA*, PAVOL PURCZ*
RAINWATER HARVESTING SYSTEM  
AND RISK MANAGEMENT APPLICATION
ZASTOSOWANIE SYSTEMU ZARZĄDZANIA RYZYKIEM 
PRZY WYKORZYSTANIU WODY OPADOWEJ
A b s t r a c t
Submitted paper presents risk assessment using risk analysis of the rainwater harvesting system. 
The aim of this article is to present selected approach in risk factors identification within 
proposed RWH system evaluation for an experimental family house. In our case, we were able 
to collect helpful information from questionnaires that later facilitated the risk identification 
as well as risk assessment phase along with the aid of brainstorming activities within a team 
of  experts. The results from the risk analysis were verified by the AHP and empirical multilevel 
comprehensive evaluation, which was also found to be useful.
Keywords: rainwater harvesting, risk analysis, risk assessment, questionnaire
S t r e s z c z e n i e
W artykule przedstawiono zastosowanie metody oceny ryzyka w odniesieniu do sytemu groma-
dzenia wody opadowej. Celem artykułu jest identyfikacja czynników ryzyka w proponowanym 
dla eksperymentalnego domu systemie RWH.  W naszym przypadku udało się zebrać przydatne 
informacje z ankiet, które później ułatwiły identyfikację oraz ocenę ryzyka. Równolegle korzy-
stano też z burzy mózgów. Rezultaty analizy ryzyka były weryfikowane przez AHP i doświad-
czalną wielopoziomową ewaluację, która okazała się także użyteczna.
Słowa kluczowe: wykorzystanie wody opadowej, analiza ryzyka, ocena ryzyka, ankieta
TECHNICAL TRANSACTIONS
CIVIL ENGINEERING
3-B/2014
CZASOPISMO TECHNICZNE
BUDOWNICTWO
180
1. Introduction
Rainwater harvesting system, although well-known all around the world, is still not well 
established in our conditions of Slovak Republic. In the past, there had been no need to look 
for new alternative water sources for domestic or commercial use because of the availability 
of good water sources in Slovak Republic. Furthermore, there are still voices that support 
the claim that it still is unnecessary in our conditions. However, overloaded sewerage 
systems and water treatment plants, cases of urban floods or water scarcity make us consider 
the sustainable usage of water sources all around the world and about proper water quality 
usage for different purposes [1]. That is the reason why we are interested in this topic and 
why we would like to increase awareness of this topic in our conditions as well. Relevant 
information on the developments in the field were obtained for the purpose of this article 
from the following reading materials listed in the reference section of this paper: [10‒15]. 
As with all human activities this system could potentially be risky in some cases, as well. 
Risk management has its place in science and our everyday life [8]. Water management 
in general comprises a wide range of problems ‒ especially in recent years when we started 
seeing an increasing need to manager ain water in a decentralized way. This entails the use 
of different infiltration or percolation systems or yet other ways of reusing this water. 
Generally, it is called rainwater harvesting, or RWH.
Indisputably, rainwater harvesting systems bring many benefits but, as with other areas, 
some events can be categorized as risky according to risk management.
Risk management programs generally cover five main components:
Context – What is at risk and why?
Risk identification – What and where are the risks?
Risk analysis – What is known about them?
Risk evaluation – How important are they?
Risk treatment – What should be done about them? [2].
Effective risk management requires identification of potential risks or hazards as described 
in methodology below. This methodology has been designed step-by-step in accordance with 
Water Safety Plan and WSP Manual and comprises the following stages:
1. Formation of a team of experts.
2. Description of an RWH system.
3. Risk identification.
4. Risk assessment.
5. Determination and evaluation of control measures [2].
RWH systems and other sustainable urban drainage systems undeniably offer many 
benefits, but as in others areas, some events can be categorized as risky from the perspective 
of risk management. The objective of risk analysis is to detect these potential risks, summarize 
them, determine their importance and find out the solution for how to prevent or eliminate 
them.
1.1. Questionnaire as a tool for risk analysis
The questionnaire was completed by designers and construction companies in Slovakia 
and it should provide many ideas, opinions and experiences related to the design process as 
181
well as to the construction and operation of such systems. Hopefully the questionnaire will 
help identify and assess risks.
The questionnaire was completed by 63 respondents. Not all of the respondents, however, 
felt knowledgeable enough to answer all of the questions.  The last part of the questionnaire 
focused on the risks in RWH, as described below, and was assessed by 20 respondents. 
At the beginning of the questionnaire there were a few basic questions about the respondents 
pertaining to their experience, position and opinion about RWH. The second group 
of questions focused on practical experiences, such as for example: when did you produce 
your first design?, what problems did you face during the design process?, have you seen 
an increased demand for RWH in recent years?, what standards or manuals do you use for 
your designs?, etc. Finally, the target of the last group of questions was to obtain information 
about the risks involved in RWH.
This part is strongly subjective as it is based on a respondent’s experiences and opinions. 
In this section we will introduce a few results obtained through the last group of questions 
in the questionnaire where respondents were asked to assign values ranging from 1 to 10 
(1 referring to the lowest risk, 10 having the highest risk) to the main parts of the system 
(as shown in Fig. 2) contingent on the significance of the risk. The results show that the riskiest 
parts of the system according to questionnaire responses are: the pump, the filter, and the tank. 
Accordingly, we can say that the greatest attention should be paid to the design, installation 
and maintenance of these three parts of the system. Approximately half of the respondents 
think that there is a lack of information about system maintenance and water usage by users 
which pins our attention also to this kind of risk. We can say that the questionnaire is a good 
example of how to obtain relevant practical information about the design process, experiences 
and opinions on the risk analysis steps such as risk identification and risk assessment.
Fig. 1. Sample of results obtained from the questionnaire – according to [7]
182
2. Risk analysis –aims and methods
The aim was to prepare a general risk analysis methodology for rainwater harvesting 
systems. This methodology can especially be applied to small scale projects such as family 
houses. In our case, it was applied to a newly constructed family house with a RWH system 
(see Fig. 1). The installed system is brand new and supplied with a 4 m3 underground water 
tank. Rainwater is used for flushing toilets, irrigation, property maintenance, and potentially 
for washing machine usage as well.
One of the aims of this risk analysis is to prepare a check-list for this type of user. 
The check list should serve as a tool for standard system checks which can eliminate various 
types of  events and also inform the user about the system. The methodology was designed 
in accordance with Water Safety protocols mentioned in section 1.
Quantitative or qualitative methods can be used for the risk evaluation. A semi- 
-quantitative methodology was selected for the RWH evaluation of our experimental 
system. The semi-quantitative risk assessment is a method for differentiating risks, focusing 
on the big issues, and managing the entire risk portfolio better. The scoring system is 
inherently imperfect, but so is any other risk evaluation system [3].
By using the semi-quantitative risk assessment method, the team of experts who 
is performing the evaluation can calculate a priority score for each identified hazard. 
The objective of the prioritisation matrix is to rank hazardous events to provide a focus on 
the most significant hazards. The likelihood and severity of these events can be derived from 
the team’s technical knowledge and expertise, historical data and relevant guidelines [2].
For the purposes of risk identification and assessment, the RWH system was divided into 
4 parts according to Fig. 3. These four parts have thus subdivided our system into 4 main 
evaluation folders. Each part was then divided into sub-systems. A sub-system en compasses 
Fig. 2. Experimental family house and RWH system (1a ‒ gutters, 1c, 1b ‒ filters 1d water 
level sensors, 2 ‒ tank, 3 ‒ pumps, 4 ‒ floating suction assembly, 5 ‒ safety overflow, 
6 ‒ label –non-potable water)
183
main system components where all sorts of potential hazards – ranging from minor ones 
to those most important – can be identified. These potential hazards constitute a list which 
constitutes the last level of our evaluation hierarchy. This final list is not presented in this 
article.
The objective of our work was to prepare risk analysis methodology for small scale RWH 
projects in particular. The methodology was applied on an experimental family house with 
an RWH system where rainwater will be used for flushing toilets, irrigation and potentially 
for washing machine usage as well.
The risk score consistent with semi-quantitative methodology is determined in accordance 
with this formula [4]:
Risk = likelihood of occurrence x severity of consequence
The risk is determined by multiplying these two values. This approach allows us to 
distinguish serious risks from minor ones and to determine priorities both for their prevention 
and their elimination.
T a b l e  1
Table of risk scores resulting from the semi-quantitative risk matrix
risk score 1‒3 4‒6 8‒10 12‒16 20‒25
risk rating very low low medium high very high
All potential hazards with a risk score of 9 or higher were taken into further consideration. 
The risk score value of 9 constitutes our point of division. This value was chosen by the team 
of experts based on their knowledge; it is a noticeably subjective value.
Fig. 3. Flow diagram: A ‒ catchment, B ‒ storage, C ‒ distribution, D ‒ user-each part was 
divided into subsections (A1, A2, A3, B1, etc.) and the last level of our system contains 
potential hazards (A11, A12, A13, A21, A31)
184
The team can choose whatever point of division or can consider all of the potential 
hazards. However, we have chosen this value and have taken into further consideration and 
evaluation only those potential hazards with the risk score of 9 or higher. These potential 
hazards can be found in Table 2.
T a b l e  2
Identified potential hazards with the risk score of 9 or higher
sub-system potential hazards
location
microbiological contamination
dustiness
drought
guttering modificationand maintenance
filters upgrade and maintenance
tank
under sizing
over sizing
microbiological contamination
upgradeand maintenance
pump clogging
WC flushing
toilet lid closing
joint bathroom and toilet
inhalation of dangerous microbes
We have observed that the risk level of the system is not high at all. What is the most 
important aspect of this RWH system evaluation are thorough and regular system upgrades 
and maintenance and good knowledge of the system function by its users.
The results of this semi-quantitative risk analysis were verified by other mathematical 
methods and a questionnaire. The questionnaire facilitated the identification and assessment 
of risks. According to the respondents (who included construction companies’ staff and 
other professionals) the parts of the RWH system most risk-prone include the pump, filters 
and the tank. We can find these parts mentioned in the results section of our risk analysis 
as well.
The mathematical method was also useful in this process. The most objective and 
appropriate method amidst mathematical methods is the AHP (which stands for Analytic 
Hierarchy Process). The highest significance as indicated by this method was attributed to 
location, pump, filter and tank. These verification methods show that the results obtained 
through the semi-quantitative method can be considered valid. Based on that, easy-to-use 
control measures for the RWH systems can be designed in order to reduce potential hazards 
to minimum or eliminate them even if the system is considered non-risky.
185
3. Discussion and conclusion
What must be indicated is that even if we focus our attention only on some parts 
of  the system, its other component parts are equally essential due to the interconnectedness 
of the system. Failure to maintain one part the system can lead to potential risks in its other 
parts. Good knowledge of the system being used is equally imperative [5].
It must also be mentioned that even if we work with numbers and methods which are 
considered objective, the interpretation of given evaluations and evaluation input is subjective 
and based on the knowledge of a team of experts. In this kind of evaluation it is impossible 
to exclude a level of subjectivity [6].
The risk assessment provides a checklist for users of RWH systems, enabling them to 
use this list of questions to perform regular system checks, to be informed about their system 
and serving also as a prevention tool [7].
3.1. Conclusion
Systems using rainwater are well-known, although they are not widespread enough in our 
country yet. The use of this alternative water resource, as well as other resources, definitely 
offers many benefits, however, the risks should not be ignored. The risks are associated with 
any activity we do in our everyday life. Early risk identification allows us to prevent potential 
hazardous events, which is crucial for proper system functioning and user satisfaction. 
In conclusion, it can be stated that most risk event-prone parts of RWH include the pump, 
filter, tank and the location itself. The goal is to design an easy-to-use risk management 
approach in order to prevent potential hazardous events, especially for small-scale RWH 
projects consistent with this experimental one.
This work was supported by the VEGA 1/0450/12 Energy balance research on rainwater management 
in the cities of the future.
The APVV ‒ SK-CZ-2013-0188 LetsTalk about the Water – An Essential Dimension of Sustainable 
Society of the 21stCentury.
R e f e r e n c e s
[1] Słyś, D., Stec A., Zeleňáková M., A LCC analysis of rainwater management variants, [In:] 
Ecological Chemistry and Engineering, S 19(3), 2012, 359-372 (retrieved from: www.scopus.
com).
[2] Water Safety Plan Manual, Step-by-step risk management for drinking-water suppliers, WHO, 
Geneva 2009.
[3] Water Safety Plans, Managing drinking-water quality from catchment to consumer, WHO, 
Geneva 2005 (http://www.who.int/water_sanitation_health/dwq/wsp170805.pdf).
[4] Očipová D., Teoretická a experimentálna analýza distribučných systémov teplej vody z hľadiska 
mikrobiologického znečistenia, Dizertačná práca, TUKE, 2009.
[5] Karelová Z., System of RWH evaluation, Young Scientist 2013, The 5th PhD, Student Conference 
of Civil Engineering and Architecture, TUKE, 2013.
186
[6] Karelová at col, Risk analysis for RWH system and its verification by mathematical methods.
[7] Vranayová Z., Karelová Z., Káposztásová D., Riziková analýza a využívanie zrážkovej vody z po-
vrchového odtoku, [In:] Sanhyga 2012, 17, vedecko ‒ odborná medzinárodná konferencia, SSTP 
Bratislava 2012.
[8] Peračková J., Markovič G., Využitie zrážkovej vody z povrchového odtoku v budovách, [In:] TZB 
Haustechnik, Roč. 18, č. 5, 2010, s. 34-37.
[9] N.F. Gray Phd.Sc.D., Water Technology (Third edition), An Introduction for Environmental 
Scientists and Engineers, Chapter 23, IWA Publishing, 2010.
[10] The Water Framework Directive, Directive 2000/60/EC of the European Parliament and 
of  the Council.
[11] Kinkade-Levario H., Design for Water: Rainwater Harvesting, Stormwater Catchment, and 
Alternate Water Reuse, New Society Publishers, 1 edition (1 June 2007).
[12] Lancaster B., Rainwater Harvesting for Drylands and Beyond, Volume 1, 2nd Edition: Guiding 
Principles to Welcome Rain into Your Life and Landscape, Rainsource Press, Revised second 
edition edition (1 July 2013).
[13] Minnesota Stormwater Manual (2008), Version 2, Minnesota Pollution Control Agency, online: 
http://www.pca.state.mn.us/index.php/view-document.html?gid=8937 ‒ 24.08.2010.
[14] Semadeni-Davies A., Bengtsson L., Theoretical Background, Chapter 1 [in:] Urban Drainage 
in Specific Climates, Vol II, Urban Drainage in Cold Climate, IHP-V Technical Documents 
in Hydrology, No. 40, UNESCO, Paris 2000.
[15] Scholes L. (2007), Stormwater reuse: why, how and where?, SWITCH ‒ presentation, 
online: http://switchurbanwater.lboro.ac.uk/outputs/pdfs/WP2-1_PRS_Stormwater_reuse.pdf ‒ 
21.09.2010.
[16] Water cycle safety plan framework, proposal, PREPARED 7th FP, 2010.


Rainwater harvesting system and risk management application

http://www.ejournals.eu/sj/index.php/Cz/article/download/1472/1507

Rainwater harvesting system and risk management application

Abstract

Similar works

Full text

Available Versions

Portal Czasopism Naukowych (E-Journals)