Dr Sarah Ward

Rainwater harvesting –

challenges & opportunities aka

“thinking outside the tank”

Universidad Industrial de Santander, Bucaramanga, Colombia, 12—10-2017

What is rainwater harvesting (RWH)?

Where does the RWH niche fit in the water landscape?

– technological innovation system

You are here

From a slide I presented in London in 2011… (http://slideplayer.com/slide/7323685/)

Challenges

• Conflicting Messages

• Unclear Guidance

• Energy Consumption in Context

• Uncertainty on scale and skill

Opportunities

• Assessing Receptivity/Acceptability

• Perceptions of Health and Safety

• Evidence for Water Saving Efficiency

Moving towards ‘Safe & SuRe’ RWH

Threat

SystemConsequences

Impact

Learn Mitigate

Cope Adapt

What do we mean by ‘Safe & SuRe’?Safe ≈≈≈≈ Reliable - “the degree to

which the system minimises

level of service failure

frequency over its design life

when subject to standard

loading”:

Rel = min (failure: probability)

Sustainable (Su) - “the degree

to which the system maintains levels of service in the long-

term whilst maximising social, economic and environmental

goals”:

Sus = max (capital: social, economic, environmental)

Resilient (Re) - “the degree to which the system minimises

level of service failure magnitude and duration over its

design life when subject to exceptional conditions”:

Res = min (failure: magnitude, duration)

“Individual systems of

provision, such as

water infrastructure

and water resources”

“The degree of non-compliance with

the defined level of service”

“Efforts to increase system

reliability and resilience”

“Better protected or

prepared”

“Any outcomes and effects of the impacts

(i.e. non-compliance with a level of service)

on each pillar of sustainability”

“Any event with the potential to reduce the degree to which the

system delivers a defined level of service”

“Embedding experiences and new

knowledge in best practice”“Reducing the threat”

Interventions

e.g. RWH

Opportunity: making RWH reliable

Verify performance against a required level of service

(India)

Design for it (prevention)

Treat it (cure)

Opportunity: making RWH reliable

Exeter

Inlet (no/ml) Tank (no/ml) Outlet (no/ml)

PCV Range Mean Std.

Dev.

Range Mean Std.

Dev.

Range Mean Std.

Dev.

Coliform 0 0-510 185 203 N/A 0 N/A N/A 0 N/A

E. coli 0 0-210 57 75 N/A 0 N/A N/A 0 N/A

Enterococci 0 0-900 229 309 N/A 0 N/A N/A 0 N/A

P. aeruginosa confirmed

(presumptive)N/A 0-1 (0-1000) N/A

(264)

N/A

(352)

0 (0-

110)

N/A

(18)

N/A

(41)

0 (0-

1000)

N/A

(287)

N/A

(487)

Ward et al (In preparation)

Multi-scale performance of

an off-grid water treatment

device. TBC

Full removal of pathogens

(where source water is selected carefully)

Opportunity: assessing environmental impact

of RWH technologies

Challenge: reducing that environmental impact

Figure 4. Relative LCIA results for 1 m3

of potable water from centralized

supply and the decentralized RHW

RainSafe system under different UK

electricity supply scenarios (the option

with the highest impact in each

category is shown as 100%)

Challenge: tackling the tech – ‘old’ systems

• Mostly German

tech – does it

really fit the UK?

• Designed to

maximise water

saving – what

about other

threats/failure

states/impacts?

Opportunity: new systems & business models

¨Smart¨ RWH

Mitigate

Adapt

“Efforts to increase system

reliability and resilience”

“Reducing the threat”

Threat: population growth

Failure mode: demand increase

Impact: supply deficit

Adapt: RWH to increase potable

water saving efficiency

Threat: climate change (averages)

Mitigate: RWH systems with lower operational

energy to reduce CO2 emissions & lessen CC

Threat: urban creep

Failure mode: increased runoff to sewer

Impact: flooding (pluvial or sewer)

(Mitigate: install permeable paving/enforce planning controls)

Adapt: install RWH (or PP) to reduce stormwater flow

Threat: climate change (extremes)

Failure mode: CSO spill

Impact: point-source pollution

Adapt: RWH to minimise sewer

discharge (frequency & volume)

Opportunity: making RWH resilient, sustainable

Challenge: getting decision makers to adopt these indicators

Driver Target

D1 Capital cost of system T1 Minimize capital cost of RWH system

D2 Water Efficiency T2 Maximize water saving efficiency of system

D3 Reduction in operational energy

consumption for rainwater supply

T3 Minimize energy used to supply water

D4 Reduction in stormwater flow T4 Minimize discharge (rate and volume) of

rainwater during storms

D5 Reduction in combined sewer

overflow

T5 Minimize discharge (frequency and volume)

of sewer network spills downstream of the site

Challenge and opportunity: multi-objective

assessment of new systems

Challenge: getting decision makers to adopt these indicators

http://www.rainwaterharvesting.co.uk/downloads/brochures/rain-activ-brochure.pdf

http://www.waterpoweredtechnologies.com/page.php?id=20

http://www.flushrain.co.uk/

Re-designing assessment

of new systems

Identifying

RWH systems

in this space

Challenge: assessing all systems

Challenge: getting new RWH

configurations into the market

Opportunity: assessing the UK RWH niche/network

Social network analysis

UK RWH niche – what are the strong points?

Influence range closeness centrality (IRCC)

hierarchy for the rainwater harvesting network

• Strong technology:

RWH innovators

• Strong networks &

forums

• Plenty of innovation

without financial

incentive (e.g. from

Government)

• Rise to challenge of

meeting SuRe drivers

(low energy,

maintenance etc)

CWS

UKRMA

RWH niche – what are the weak points?

• Small, dense, disconnected from the “bigger picture”

• Heavy bias of RWH innovators & overlapping networks

• Innovation in isolation – not priority for policy/decision

makers

• Policy makers are poorly represented

• Policy makers focus on evidence of meeting

(undefined) drivers e.g. energy consumption (no target)

• End-users are not represented

• Few social enterprises

Opportunity: niche governance (i.e. not management)

Respond to

regime

sust’y aims

Tech, soc

& service

innovation

Dynamic &

reflexive

learning

Persuasive &

influential

intermediaries

No

protected

spacesNetwork

with/out

converged

expectations

Polycentric

governance –

including end-

users

Rainwater

Users Forum?

Critical analysis & reflection on a

range of data sources/knowledges

led to definition of 7 niche

governance categories:

Opportunity: include end users…look at the tank from both sides

• Co-create evidence (e.g.

performance data, energy

consumption, cost-benefit)

• Critically evaluate all RWH

configurations/enterprises

Grupo de Investigación en Recursos Hídricos y

Saneamiento Ambiental:

End-User Cost-Benefit Prioritization for

Selecting Rainwater Harvesting and Greywater

Reuse in Social Housing

Isabel Domínguez, Sarah Ward, Jose Gabriel

Mendoza, Carlos Iván Rincón & Edgar Ricardo

Oviedo-Ocaña

Financial feasibility of end-user designed

rainwater harvesting and greywater reuse

systems for high water use households

Edgar Ricardo Oviedo-Ocana, Isabel

Dominguez, Sarah Ward, Miryam Lizeth Rivera-

Sanchez & Julian Mauricio Zaraza-Pena

Ongoing work by GPH at

different building scales

Opportunity: community/social enterprise

What happens elsewhere?

Mexico

• Connecting people with too much

runoff with those who need more!

• Including the end-user - making

space for people

• Reconnecting people with water –

giving back ownership

• Helping communities

grow/wash/flush (swapping non-

potable for potable)

• Keeping rainwater out of

sewers/slow its entry to sewers (local

source control)

rainshare.co.uk

Changing the world, one roof at a time……

What’s happening in

the UK?

in action……

rainshare.co.uk

http://waterenergynexus.co.uk/rainshare/

Need more RainSharers!

= distributed communal harvested rainwater storage

Project A – Commercial - Residential

Exploring other potential projects

Project B - Residential/domestic

Project C – Urban Greening

Taxi firm washing 3 cars, 2-3 times/week

Reflecting on where we are with the challengesWe can:

• Size & design tanks using a number of methods

• Verify performance to specified levels of service (e.g.

demand requirements, water quality standards)

• Reduce threats (e.g. energy use/carbon emissions)

• Reduce (negative) consequences (e.g. lower capital cost)

• Increase (positive) consequences (e.g. higher water

saving efficiency; end-user participation)

• Contribute to stormflow reduction (helping adapt the

drainage system to extreme conditions)

• But we must do it across international case

studies & there are many more things to do…

What next?

“We are often water-short when demand is greatest.

And now our climate is changing. What are the

implications and opportunities for rainwater

harvesting as a source of water for potable and non-

potable uses?"Kim Stephens, Partnership Executive Director

(Tracking Adaptation & Measuring Development (TAMD))

• Multi-objective, reliable, resilient,

sustainable RWH for all?

• Combining technical & social innovation

• For non-UK contexts finding out the ‘how’

• Much more research going on in this area

References for work shown in this presentation can be found at:

http://emps.exeter.ac.uk/engineering/staff/sw278/publications

Thank you

¿Preguntas?

¿como es en colombia?