Effect of Climate Change on Sewer Overflows in Milwaukee WEFTEC 2012 October 2012 Bridging the gap...

Effect of Climate Change on Sewer Overflows in Milwaukee

WEFTEC 2012

October 2012

Bridging the gap betweenclimate change research andthe risk of overflows from my collection systemDavid Perry

Brown and Caldwell, Milwaukee, Wisconsin

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David Perry


Presenter

David Bennett, Brown and Caldwell

Urbain Boudjou, Tim Bate, and Karen Sands, Milwaukee Metropolitan Sewerage District

Michael Hahn, Southeast Wisconsin Regional Planning Commission

Sandra McLellan and Elizabeth Sauer, Great Lakes WATER Institute, University of Wisconsin, Milwaukee

Co-Authors

http://mmsd.com/defaulttwo.aspx

http://www.sewrpc.org/

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Climate change research is producing a wealth of models and projections on global climate change …

What does that mean to my organization in our local context?

What is the possible risk of overflows in the future?

Will our long range facilities plans be ruined by climate change?

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• Milwaukee – our context• Regional Climate Change Trends• Downscaling: from Regional to Local• Milwaukee Modeling System• Findings

Outline

Milwaukee – our contextSome background to the key questions

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Milwaukee• Three rivers meet Lake Michigan• 850 square miles drain to Milwaukee Harbor

Pollution Sources:• Urban runoff• Agricultural runoff• SSOs• CSOs

Great Lakes - 20% of Earth’s freshwater

Drinking water source for 40M

500 beaches

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• Serves Milwaukee and 27 metropolitan communities

• 1 million people• 5% Combined Sewers, 95% Separated Sewer

• Two large water reclamation facilities• Total treatment capacity 690 MGD

• Deep Tunnel Storage – 427 MG • CSO and SSO control

• Real Time Control• Optimize use of treatment and storage

Milwaukee Metropolitan Sewerage District


2020 Facilities Plan

• Innovative watershed-scale approach – Collaborative, Integrated• Wastewater system + water course system

• Improve water quality in regional streams/rivers and Lake Michigan.

• Facilities plan + Regional water quality management plan

• Completed in 2007 • Did not account for climate change.

Regional Water Quality

Management Plan




Regional Water Quality Plan

Will the plan work if climate changes?

Can we meet goals for SSO and CSO control?



Regional Climate TrendsA few observations

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How will our climate change?

http://www.wicci.wisc.edu/climate-change.php

Large events may become larger and more frequent

Smaller events may become less frequent

Total annual rainfall may be similar to existing – but the distribution of rainfall may vary

Probability of Snow vs. Rain

Courtesy of Dan Vimont

Only a 1-month snow season in Milwaukee later this century?

Late 20th c(1950-1999)

Late 21st c(2080-2099)IPCC Scenario A2

Climate models and uncertainty

• Global Climate Models (GCM)• 14 models• Wide range in predicted

results

Strategy: Use two GCM models that

represent the best and worse case scenario for our most

sensitive season for generation of CSOs:

SPRING RAINFALL

Downscaling to LocalHow to convert regional model results to local data

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Climate Downscaling UW-Madison Center for Climate Research

• Approaches• Statistical downscaling (GCM)• Dynamic downscaling (regional climate models)

• Statistically downscaled precipitation and air temperature time series • Projected mid-century climate change conditions • Parent data: Milwaukee airport observed data for the 1940 through mid-2004

period.

GCMGridCells

Local8 km x 8 kmGrid cells

Milwaukee Modeling SystemHow do we link climate projections to overflow estimates?

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Modeling Methods used by MMSD

Rainfall and Meteorological Data

Regional Hydrologic Model

HSPF Continuous runoff and infiltration simulation

(used for both wastewater and stormwater/watercourse modeling)

Wastewater Flow Generation Model

Flow Forecasting System (FFS)

Calibrated wastewater hydrographs

Wastewater Hydraulic Model

MikeUrbanDetailed simulation of

level and flow in all pipes and facilities

Simplified Wastewater Flow Generation and Hydraulic Model

MACRO

System-wide water balance simulation of flow and volume

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Modeling Methods used by MMSD

Rainfall and Meteorological Data

Regional Hydrologic Model

HSPF Continuous runoff and infiltration simulation

(used for both wastewater and stormwater/watercourse modeling)

Wastewater Flow Generation Model

Flow Forecasting System (FFS)

Calibrated wastewater hydrographs

Wastewater Hydraulic Model

MikeUrbanDetailed simulation of

level and flow in all pipes and facilities

Simplified Wastewater Flow Generation and Hydraulic Model

MACRO

System-wide water balance simulation of flow and volume

StrongHydrologicFoundation

Decades of history rapidly simulated to predict SSOs and CSOs

FindingsWill the plan work?

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Case 1: 2010 Existing Facilities + Historic Climate

Case 2:Recommended Facilities + Historic Climate

Case 3:Recommended Facilities + DSN10%

Case 4:Recommended Facilities + DSN90%

Simulation CasesPopulation and

Land Use Condition

FacilitiesRepresented in

the ModelClimate Scenario

All cases usedProjected

Future 2020Population and

Land Use

Baseline


Moderate climate change

More extreme climate change

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Simulated SSO Volume in Each Year

64 year simulation

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2010 Facilities + Historic climate

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64 year simulation

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Recommended 2020FP + Historic climate

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64 year simulation

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Recommended 2020FP + DSN 10%


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0

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CS

O (

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/yr)


Simulated CSO Volume in Each Year

64 year simulation

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64 year simulation

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64 year simulation

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Recommened 2020FP + DSN 90%

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Average Annual Simulation Results

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2010 Facilities Recommended 2020FP Recommended 2020FP Recommended 2020FP Avg

Annu

al R

ainf

all (

inch

es)

Avg

Annu

alTe

mpe

ratu

re (d

eg F

)

Aver

age

Annu

al O

verfl

ow V

olum

e (M

G/y

ear)

CSO SSO Rainfall Temperature

Historic Climate Historic Climate DSN 10% Climate Change

DSN 90% Climate Change

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• Large events may be larger and more frequent

• Small events may be less frequent• The annual average rainfall may have a

similar average amount• Increasing spring rainfall is a characteristic of

most GCM results• Spring is also the time of greater CSO risk

• Increasing temperature may reduce the likelihood of snowmelt events

Summary on climate change

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• Recommended Facilities in the 2020 Plan are designed to reduce overflows (especially SSOs)

• Year-to-year variability in overflows is large• For both the existing climate and projected climate scenarios

• Climate change may increase CSOs • Up to 20% more average annual CSO volume in the extreme

climate scenario• But annual SSO volume may not change significantly

• The objectives of the 2020 Plan are not significantly compromised in the climate change scenarios• Additional facilities could be constructed to mitigate the

changes

Conclusions – for Milwaukee MSD

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• Build a team• Climate researchers• Hydrologic and hydraulic modelers• Wastewater system planners and managers• Water quality scientist

• Evaluation of climate change on overflows requires:• Downscale GCM to local - statistically modify

historic weather • Model with strong hydrologic foundation• Simulate long term response to climate scenarios• Keep hydraulic model simple

Conclusions – in general

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David Perry


Presenter

David Bennett, Brown and Caldwell

Urbain Boudjou, Tim Bate, and Karen Sands, Milwaukee Metropolitan Sewerage District

Michael Hahn, Southeast Wisconsin Regional Planning Commission

Sandra McLellan and Elizabeth Sauer, Great Lakes WATER Institute, University of Wisconsin, Milwaukee

Co-Authors

Let’s talk about it …

I welcome your comments and

questions



Effect of Climate Change on Sewer Overflows in Milwaukee WEFTEC 2012 October 2012 Bridging the gap...

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Transcript of Effect of Climate Change on Sewer Overflows in Milwaukee WEFTEC 2012 October 2012 Bridging the gap...