Paper presented at the International Water Association (IWA) Efficient Conference 2017, Bath, UK 18-20 July

1. Modeling Water Demand in Droughts
(in England & Wales)
(IMPETUS Project: Estimating Scenarios for Domestic Water Demand Under
Drought Conditions in the UK: Application of a Microsimulation Model)
Dr. Despina Manouseli, Dr. Ben Anderson & Dr.
Magesh Nagarajan
Sustainable Energy Research Group
Energy & Climate Change Division, Faculty of Engineering & Environment

2. IMPETUS: Modeling Water Demand in Droughts
Contents
 The problem
 Model Framework
 Concepts & Implementation
 Preliminary Results
 Next Steps
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3. IMPETUS: Modeling Water Demand in Droughts
The problem:
Water Stress
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2050
 With no ‘behaviour’ change and no flow controls:
Source: DEFRA, 2011

4. IMPETUS: Modeling Water Demand in Droughts
The problem: Water Stress
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 Supply:
 Locally/regionally scarce
 Climate change effects?
-Prolonged lack of rainfall
-Lack of ground water recharge
 Demand:
 >50% used by households
 Drivers not well understood
 Climate change effects?
-No rain-More water needed to water
gardens
 Demographic:
 Population growth
 Increasing single person households

5. IMPETUS: Modeling Water Demand in Droughts
The problem: current practice
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Sources: Water UK (2016) Water resources long term planning framework (2015-2065), Essex & Suffolk Water,
Daily Mail
Water Resources Long Term Planning Framework
Water UK
Figure 3-4 Illustration of typical sequence of drought interventions (taken from the Affinity Water
Drought Plan)
Example diagram of a drought trigger-response system. The purple and blue lines represent theoretical
monitored groundwater levels during a two or three year event respectively. The green, yellow, orange and
red bands represent ‘thresholds’ that are based on an analysis of historic records, and are used to help
inform the company when it is making decisions on the level of demand restrictions and supply side
interventions to take.
The y-axis in this indicative diagram, presents the groundwater level (in metres above ordnance datum,
mAOD).
Severity Levels
Drought & Severe
Drought: hosepipe
bans for households
Severe Drought:
- Increased abstraction for
Public Water Supply outside
that permitted by an
abstraction license
- Restrict abstraction for
agriculture
- Rota-cuts and standpipes
MAYBE ONCE IN 200 YRS
Most Companies plan
based on the worst
drought over 100 yrs of
records. But.. the climate
is changing and the
population growing!

6. IMPETUS: Modeling Water Demand in Droughts
How can we mitigate a potential supply-demand deficit-at
the household level?
 Water Efficiency
 Metering-still less than 50% in the UK
 Leakage Reduction
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7. IMPETUS: Modeling Water Demand in Droughts
Contents
 The problem
 Model Framework
 Concepts & Implementation
 Preliminary Results
 Next Steps
7

8. IMPETUS: Modeling Water Demand in Droughts
IMPETUS: joined-up modelling…
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RCUK Funded under the UK Droughts & Water Scarcity Programme 2014-2017
IMPETUS: Improving Predictions of Drought for User Decision-Making
Meteorological
Models
Hydrological
models
Demand
models

9. IMPETUS: Modeling Water Demand in Droughts
The Water Demand Model
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• ‘Normal’ demand of a synthetic sample of
households
• Drought histories
Inputs
• Impact of ‘drought’ (Drought histories
provided by CEH)
• Impact of ‘interventions’
Microsimulation Model
• Estimated demand under drought-
Retrospectively
Outputs
For a given catchment…

10. IMPETUS: Modeling Water Demand in Droughts
Climate data matched against CEH
drought histories
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11. IMPETUS: Modeling Water Demand in Droughts
The Water Demand Model
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Q1 1995
•Drought phase X -> Estimated demand
Q2 1995
•Drought phase X -> Estimated demand
Q3 1995
•Drought phase X -> Estimated demand
Q4 1995
•Drought phase X -> Estimated demand
…
•…
Q4 2014
•Drought phase X -> Estimated demand
For a given catchment…

12. IMPETUS: Modeling Water Demand in Droughts
Contents
 The problem
 Model Framework
 Concepts & Implementation
 Preliminary Results
 Next Steps
12

13. IMPETUS: Modeling Water Demand in Droughts
‘Normal’ demand model-Baseline
 A sample of 1800 h/hs. h/h sizes
representative of the 2011 UK
Census
 Appliance (micro-component) use,
litres/day (Parker, 2014) and
coefficients relating them
– With household attributes
– With weather
– By season
 Water efficiency measures (EST,
2013)
– 41% of HH have dual-flush toilet in
2011.
– 25% of HH have efficient
shower heads in 2011.
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Data source: “At home water needs” EST (2013, p13)
So what’s the point of an external use ban??

14. IMPETUS: Modeling Water Demand in Droughts
Intervention ‘impact’ model
Impact of temporary use bans, UKWIR 2013 report
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Water-use
appliance
Usage Water-
use
saving
% switch
per year
Dual-flush toilet 5 l/flush 47% 2%
Other-flush
toilet
13 l/flush
Eco-shower 5 l/min 61% 1%
Power-shower
(Others)
13 l/min
Initial values: (EST, 2013)
• Key assumptions:
• No change in practices (the user experience
is unchanged)
• Efficiency does not degrade over time
• Water efficiency uptake can be varied
• Key parameters:
• External use ~= 11% households
• TUB compliance can be varied
Type of
househol
d
% Water-use
saving
Compliance
High flow
user
14% for
Drought
28% for
Severe
10-18% 44% (6% of
total)

15. IMPETUS: Modeling Water Demand in Droughts
R
Model version_1 flow diagram
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16. IMPETUS: Modeling Water Demand in Droughts
Contents
 The problem
 Model Framework
 Concepts & Implementation
 Preliminary Results
 Next Steps
16

17. IMPETUS: Modeling Water Demand in Droughts
Model v1: Retrospective
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Census
2011
N households
Household
size
Age distribution
Work
status
Synthetic survey

18. IMPETUS: Modeling Water Demand in Droughts
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WITHOUT DROUGHT
BASELINE WATER
EFFICIENCY UPTAKE

19. IMPETUS: Modeling Water Demand in Droughts
WITH DROUGHT
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1996 Severe Drought
WITHOUT
DROUGHT
INCLUDES MORE EFFICIENCY
MEASURES

20. IMPETUS: Modeling Water Demand in Droughts
Comparison to the Baseline model
1996 Severe Drought
BASELINE
No drought measures
Baseline water
efficiency
DROUGHT MODEL
Increased water
efficiency + TUBs in
relevant drought
phases

21. IMPETUS: Modeling Water Demand in Droughts
Comparison to the Baseline model
1996 Severe Drought-Large TUB Effect
BASELINE
No drought measures
Baseline water
efficiency
DROUGHT MODEL
Increased water
efficiency + TUBs in
relevant drought
phases

22. IMPETUS: Modeling Water Demand in Droughts
Contents
 The problem
 Model Framework
 Concepts & Implementation
 Preliminary Results
 Next Steps
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23. IMPETUS: Modeling Water Demand in Droughts
Next Steps
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 Model V_2 Adding:
– Practices
– Weather
– Interactions
 Linking to
– drought forecasts (2016-2021)

24. IMPETUS: Modeling Water Demand in Droughts
Thank you!
 d.manouseli@soton.ac.uk
 b.anderson@soton.ac.uk (@dataknut)
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