Changes in Urbanisation and its

Effects on Water Quantity and

Quality from Local to Regional Scale

Lead PI: Dr Mike Hutchins (CEH Wallingford)

• POLLCURB investigates

how water pollution

relates to change in urban

areas, in particular that

brought about by

population growth.

• UK population will

increase by 16% in next

20 years.

• Results will provide

predictions of future water

resources to help inform

decision-making.

• Focus on Thames basin

Compare 2050 Thames water quality to present day?

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DO BOD Temp chl-a

Incr

ease

in d

ays p

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ear

Wallingford

• An increase in number of days per year having undesirable water quality by 2050 (due to drier, sunnier, warmer summers)

• Moreover, this assumes no change in population. Urban growth will put greater stress on water resources…

• The projections will be refined in POLLCURB

1. Climate model (Had-RM3)

2. Rainfall-runoff model

(Future Flows) 3. Water quality model

(QUESTOR)

Models linked together in sequence to evaluate

effects of climate change

Incr

ease

in n

um

ber

of

day

s p

er y

ear

hav

ing

un

des

irab

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on

dit

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s

1. Has long-term urbanisation significantly altered the flow regime? 2. Can urban river pollution be determined by land cover data,

together with measures of infiltration capacity and rainfall regime readily available from national-level datasets?

3. How do water temperature, residence time and channel hydraulics influence the fate of pollutants downstream of urban areas?

• Simplified meta-model for upscaling to whole Thames basin. • At basin scale future scenarios will be defined by projections of

population growth, urban development, water demand management, water treatment and climate inputs.

• Future scenarios assessed using the meta-model and QUESTOR.

Research questions and model development

• To be achieved with the help of two local-scale case-

studies in The Cut (Bracknell) and River Ray (Swindon)

catchments which have undergone rapid recent

urbanisation.

1. Identify historical change in urbanisation using temporally-

consistent datasets of landcover produced from satellite

data combined with OS data sources.

2. Develop an integrated model of urban water quality and

quantity at the local-scale.

Objectives for first half of project

Case studies: towns of Swindon and Bracknell

S S

S

S Treated sewage effluent

d) 2011 c) 2007 b) 1990 a) 1975*

• Remote sensing imagery captures land-use change at 5 time points since early-1970s.

• EA water flows (since 1960s) and quality (since 1980s) • 2 years monitoring: (i) logged 15-min hydroclimatology:

rainfall at 5 sites and discharge at 8 sites (plus 6 existing sites) and (ii) telemetric hourly water quality (multi-parameter sonde: pH, turbidity, temperature, conductivity, ammonium, DO) at 3 sites via EA NWQIS.

• Also, additional multi-parameter sonde used for monthly water quality surveys at 16 sites.

Environmental data acquisition d) 2011 c) 2007 b) 1990 d) 2011 c) 2007 a) 1975* b) 1990 d) 2011 c) 2007

Land-cover change

Topographic mapping (OS)

Aerial photography

Satellite imagery

Derivation of indices of the percentage of impervious surface cover.

Calculated at basin and local scale. The 3 different sources of information

are compared where possible, making for robust estimates

Stream water monitoring

• Sites for hydrological monitoring selected,

authorised and installed in summer 2013

• Flow and water quality monitoring

commenced autumn 2013

• Suspended sediment analysis to

corroborate optical turbidity measurements

• Data quality issues include unreliable

velocity readings at low flows, in addition to

expected uncertainties at high flows

• Requires many spot gaugings to confirm

velocity measurements and calibrate rating

curves (depth-flow) at each site (ongoing

process)

• QC data from previously ungauged sites

will be available to modellers this summer.

• Data from continuous water quality sites

available in real-time.

• Satellite land-cover data and Ordnance Survey maps will train cellular automata land-use change models.

• Water flow and water quality data will train bio-physical models (rainfall-runoff, urban water management, suspended sediments, channel hydraulics/water quality).

Research: modelling approaches

From land cover change, a metric of

fractional impervious cover drives a

rainfall-runoff model to quantify

changes in hydrological regime

Part of

Swindon

Urban water management modelling

• Water demand

• Urban drainage,

water supply and

water quality

(SWMM)

• Wastewater

treatment,

discharges to

rivers (SSDIM –

has been tested

in small Chinese

urban basins e.g.

Shenzhen River)

• GLM to explain changes in mean annual conditions in Ray (Swindon) and Cut (Bracknell): Increasing discharge, temperature and DO Urban extent has a strong positive relationship with

discharge, amplified when also considering rainfall. No temporal change in analogous rural catchments Although still lower, DO levels are now approaching those in

analogous rural catchments despite the population increase (due to improvements in treatment of effluents?)

• Sub-daily flow records in Bracknell since 1950s: increase in frequency and intensity of high flow events changes most apparent in summer Without 17 new balancing ponds and flood storage areas

these changes would have been 20% more severe

Initial data-driven assessments

• Lumped rainfall-runoff modelling (DAYMOD): including a new means of simulating infiltration capacity under urban land cover. Highlights importance of leaky infrastructure.

• Urban drainage map used to model design rainfall events in the Bull Brook semi-urban sub-catchment in Bracknell. Data from previous 1990s Defra project will be used to test capability of model to capture response to urban growth.

• QUESTOR model is being extended upstream from the Thames confluences of the Ray and Cut to the gauging stations (“catchment outlets”), to link with SSDIM river routing module.

• Sediment rating curves assessed for 10 HMN sites (1974 onwards) in Thames basin - being used to assess variation in time (event-based and inter-annual analysis) and space.

Current modelling activities

Model drivers: (1) Flow, temperature and quality data in (a) tributaries (b) effluents from sewage works, (2) Solar radiation (3) Weirs (4) Abstractions

Simulates flow routing, and pollution retention and release in short river reaches (c. 3 km) on a daily basis.

CEH weekly water quality (2009 - ) Upstream QUESTOR boundary

Tidal limit

Major urban areas outside London

LONDON

20 km

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6 5

4

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2

1

8

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Model representation of River Thames (QUESTOR)

SWINDON

BRACKNELL

Earthwatch Institute run FWW (focus on urban rivers and ecosystem services). POLLCURB is contributing to provide education to citizen scientists. In turn they will widen our perspective of water quality issues.

Citizen scientists will use water quality monitoring probes and a bluetooth data collection system in west London. This will specifically enable further testing of POLLCURB models and add value to EA monitoring programmes.

Working with Citizen Scientists

A global network for water monitoring

Earthwatch: water quality in urban areas

Citizen science at global and local scales

Website: www.pollcurb.ceh.ac.uk

Contributors

• Thomas Kjeldsen (Bath)

• Soon-Thiam Khu, Scott McGrane (Surrey)

• Simon Dadson, Gianbattista Bussi (Oxford)

• James Miller, Clare Rowland, Iwona Cisowska, Luisa Doughty, Yan Weigang (CEH)

• June Jones, Matt Loewenthal (EA)

• Steven Loiselle, Charlotte Hall, Richard Sylvester (Earthwatch)

• Postgraduate students from Royal Holloway, Surrey and Cranfield

• International academic visitors from (i) University of Wageningen, (ii) K-water (South Korea)

Other Acknowledgements

Thank You