Estimating outdoor water use allowing for the possible impacts of climate change by Chikondi ...

130 Pages·2017·6.59 MB·English

Estimating outdoor water use allowing for the possible impacts of climate change
by
Chikondi Makwiza
Dissertation presented for the degree of Doctor of Philosophy in the Faculty of Engineering
at Stellenbosch University
Supervisor: Prof. H. E. Jacobs
March 2018
Stellenbosch University https://scholar.sun.ac.za
Declaration
By submitting this dissertation electronically, I declare that the entirety of the work contained
therein is my own, original work, that I am the sole author thereof (save to the extent explicitly
otherwise stated), that reproduction and publication thereof by Stellenbosch University will not
infringe any third party rights and that I have not previously in its entirety or in part submitted
it for obtaining any qualification.
This dissertation includes 4 original papers published in peer-reviewed journals or books and
1 unpublished publication. The development and writing of the papers (published and
unpublished) were the principal responsibility of myself and, for each of the cases where this
is not the case, a declaration is included in the dissertation indicating the nature and extent of
the contributions of co-authors.
Date: March 2018
Copyright © 2018 Stellenbosch University
All rights reserved
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Plagiarism declaration

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Abstract
Climate change may stress water supply systems due to both diminishing water resources
and rising climate driven water use. Reducing the sensitivity of residential outdoor water use
to climatic factors is desirable for climate change adaptation. Outdoor water use is also
attractive for achieving water savings, because outdoor use is more elastic than indoor use.
This study was aimed at estimating residential outdoor water use for the purpose of estimating
how it would be impacted by climate change.
A conceptual model was formulated to derive irrigation water use for vegetated areas around
the home from climate variables. The model was based on the modification and adaptation of
an existing residential end-use model for outdoor water demand to include climate change
parameters. The resulting irrigation water end-use model is suitable for assessing water use
for specific vegetation types maintained around the home. Application of the model to the case
of leafy vegetables grown in the backyard garden was demonstrated in this study. The growth
of vegetables in backyard gardens is often linked to nutritional food security in developing
countries, stressing the importance of research to better understand the impacts of climate
change on water use for garden irrigation.
In this research study, outdoor water use events were studied using sound recorded at outdoor
taps. The automatic detection algorithm applied to the recorded sound signals performed
reasonably well with precision and recall rates of at least 80%. Diurnal water use patterns
derived at the outdoor tap revealed time periods of peak water use.
An exploratory analysis of water billing records for the city of Lilongwe showed that water use
increased with plot size, similar to previously reported research in southern Africa. Summer
peaking factors also increased with plot size. In a follow-up study, panel linear regression
analysis was used to create an empirical relationship between household water use and the
independent variables: plot size and theoretical irrigation requirements. Predictions for
ensemble averages of temperature and rainfall projections for 2050 showed an increase of
1.5% in annual water use under the low emissions scenario and 2.3% under the high
emissions scenario.
Finally, the performance of temperature and rainfall as independent variables in water use
regression models was compared to the use of theoretical irrigation requirements. Empirical
analysis of a residential water use dataset for 12 North American cities showed that the
transformation of temperature and rainfall to irrigation requirements, using a suitable set of
parameter values, improved the performance of the water use regression models.
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The results of this study show that garden irrigation will increase due to climate change, but
the increase is relatively small compared to the expected population growth and urbanisation
in many parts of Africa. The impact of climate on expected water use was examined using
simple and effective techniques that were employed at relatively low cost. Water utilities and
planners could employ the methods and tools reported on here to better plan for the additional
expected increase in outdoor water use resulting from climate change.

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Opsomming

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Acknowledgements
I am grateful to God for providing me with strength throughout the four-year study at
Stellenbosch University.
I would like to thank Prof. H. E. Jacobs for providing valuable direction and inspiration that led
to the successful completion of this work.
The Capacity Building for Modelling Climate Change in Malawi (CABMACC) programme of
the Lilongwe University of Agriculture and natural Resources provided financial support for
which I am truly grateful.
Finally, I appreciate my family for accompanying me during my stay in South Africa.

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Table of contents
Declaration ............................................................................................................................. ii
Plagiarism declaration ........................................................................................................... iii
Abstract ................................................................................................................................ iv
Opsomming .......................................................................................................................... vi
Acknowledgements ............................................................................................................. viii
List of figures ....................................................................................................................... xi
List of tables ........................................................................................................................ xiii
List of symbols .................................................................................................................... xiv
Abbreviations and acronyms .............................................................................................. xvii
Chapter 1. Introduction .......................................................................................................... 1
Chapter 2. Makwiza, C., Fuamba, M., Houssa, F. & Jacobs, H. E. 2015. A conceptual
theoretical framework to integrally assess the possible impacts of climate change
on domestic irrigation water use. Water SA 41(5), 586–593. ............................... 7
Chapter 3. Makwiza, C. & Jacobs, H. E. 2017. Sound recording to characterize outdoor tap
water use events. Journal of Water Supply: Research and Technology-Aqua 66(6),
392–402. ........................................................................................................... 30
Chapter 4. Domestic irrigation water end-use modelling of leafy vegetables ....................... 47
Chapter 5. Makwiza, C. & Jacobs, H. E. 2016. Assessing the impact of property size on
residential water use for selected neighbourhoods in Lilongwe, Malawi. Journal of
Water Sanitation and Hygiene for Development 6(2), 242–251.......................... 54
Chapter 6. Makwiza, C., Fuamba, M., Houssa, F. & Jacobs, H. E. In Press. Estimating the
impact of climate change on residential water use using panel data analysis: a case
study of Lilongwe, Malawi. Journal of Water Sanitation and Hygiene for
Development 7(3). ............................................................................................. 71
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Chapter 7. Makwiza, C. & Jacobs, H. E. Unpublished. Improving performance of water use
regression models through the determination of optimal parameters for the
transformation of weather inputs. . ..................................................................... 89
Chapter 8. General discussion .......................................................................................... 100
Chapter 9. Conclusion ....................................................................................................... 103
References ....................................................................................................................... 106
Appendix A: Declarations of candidate and co-authors ..................................................... 108
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