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

IMPETUS: Modeling Water Demand in Droughts Contents § The problem § Model Framework § Concepts & Implementation § Preliminary Results § Next Steps 2

IMPETUS: Modeling Water Demand in Droughts The problem: Water Stress 3 2050 § With no ‘behaviour’ change and no flow controls: Source: DEFRA, 2011

IMPETUS: Modeling Water Demand in Droughts The problem: Water Stress 4 § 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

IMPETUS: Modeling Water Demand in Droughts The problem: current practice 5 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!

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 6

IMPETUS: Modeling Water Demand in Droughts Contents § The problem § Model Framework § Concepts & Implementation § Preliminary Results § Next Steps 7

IMPETUS: Modeling Water Demand in Droughts IMPETUS: joined-up modelling… 8 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

IMPETUS: Modeling Water Demand in Droughts The Water Demand Model 9 • ‘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…

IMPETUS: Modeling Water Demand in Droughts Climate data matched against CEH drought histories 10

IMPETUS: Modeling Water Demand in Droughts The Water Demand Model 11 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…

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

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. 13 Data source: “At home water needs” EST (2013, p13) So what’s the point of an external use ban??

IMPETUS: Modeling Water Demand in Droughts Intervention ‘impact’ model Impact of temporary use bans, UKWIR 2013 report 14 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 househo ld % Water-use saving Compliance High flow user 14% for Drought 28% for Severe 10-18% 44% (6% of total)

IMPETUS: Modeling Water Demand in Droughts R Model version_1 flow diagram 15

IMPETUS: Modeling Water Demand in Droughts Contents § The problem § Model Framework § Concepts & Implementation § Preliminary Results § Next Steps 16

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

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

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

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

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

IMPETUS: Modeling Water Demand in Droughts Contents § The problem § Model Framework § Concepts & Implementation § Preliminary Results § Next Steps 22

IMPETUS: Modeling Water Demand in Droughts Next Steps 23 § Model V_2 Adding: – Practices – Weather – Interactions § Linking to – drought forecasts (2016-2021)

IMPETUS: Modeling Water Demand in Droughts Thank you! § [email protected] § [email protected] (@dataknut) 24