Utility Climate Resiliency Study

June 9, 2016Danny Johnson, Manager

Outline• Goals of Utility Climate Resiliency Study• Potential Future Climate Conditions• Methodology and Findings for Vulnerability

Analysis:

• Infrastructure and Policy Adaptation • Summary

FloodingWater Supply Water QualityWater Demand

Goals of Utility Climate Resiliency Study

• Produce a plan for the District that can be used to guide future planning efforts

• Assess potential vulnerability of water resources and related infrastructure given potential climate conditions in the future: – Not Predictive: The purpose was NOT to predict

future climate conditions or the likelihood that certain conditions could occur.

– Readiness: The purpose WAS to identify potential climate conditions that, if they do occur, could create specific risks.

Possible Future Climate Conditions5 representative scenarios of possible future climate conditions based on GCMs

1 additional scenario developed by extending historic records through 2050.

Goal was to boundthe possibilities

HOT/DRY HOT/WET

WARM/WETWARM/DRY

0

10

20

30

40

50

60

70

80

1950 1960 1970 1980 1990 2000

Annu

al A

vera

ge Te

mpe

ratu

re ('

F)

Year

2050 Central Tendency

2050 Hot/Dry

2050 Hot/Wet

2050 Warm/Dry

2050 Warm/Wet

2050 Historical Trend

Historical Observed

Range of Annual Temperature Change:1 to 7 ºF

Future Climate Scenarios: Annual Temperature

Also have daily data to assist with looking at seasonal trends

Future Climate Scenarios: Annual Precipitation

0

10

20

30

40

50

60

70

80

1950 1960 1970 1980 1990 2000

Annu

alPr

ecip

itatio

n (in

)

Year

2050 Central Tendency

2050 Hot/Dry

2050 Hot/Wet

2050 Warm/Dry

2050 Warm/Wet

2050 Historical Trend

Historical Observed

Range of Annual Precipitation Change:-2 to +11 in/yr

Methods and Findings

Analysis of Water Demands:As a function of Policy, Economics, and Climate

200

250

300

350

400

450

500

Economic Recession

Level 1 Drought Restrictions

Level 4 Drought Restrictions

GA Water Stewardship Act

Dry Periods Wet Periods

Wat

er D

eman

d (M

GD)

DeKalb, Fulton and Gwinnett Counties as Proxy

Water Demand: Sensitivity to Climate via Multivariate Regression

Long Term Potential Impacts of Climate Variability:Per Capita Water Use (by 2050)*

* Average increase, with all other factors unchanged.

Water Supply: Evaluated Firm Yield of 5 Small/Midsize Reservoirs

Reservoir CountyStorage Volume

(BG)

Drainage Area

(sq.mi.)

Percent watershed developed

Estimated Average

Flow (cfs)Dog River Reservoir Douglas 1.9 78.3 15.4 117

Randy Poynter Reservoir Rockdale 5.4 47.0 38.5 78

Long Branch Reservoir Henry 1.5 4.3 8.3 5

Gardner Reservoir Henry 0.7 16.9 35.9 21

Upper Towiliga Reservoir Henry 6.0 29.4 13.1 40

Firm Yield In Case Study Reservoirs

0

5

10

15

20

25

30

35

Dog River Randy Poynter Gardner Long Branch Cole/Tawiliga

FIRM

YIEL

D (M

GD)

Potential Impacts of Climate Trends on Firm Yield

Central Tendancy Hot Dry Hot Wet Warm Dry Warm Wet Trend Projection Historic

• Climate trends could change reservoir yield by -10% to + 30%.• Drought severity does not always equal the impact:

– Large reservoirs are more sensitive to long-term droughts.– Small reservoirs can be more sensitive to short severe droughts.

• No clear physical predictors of risk level• Changes in yield would be coupled with increased demand.• Important to understand the risks for each individual supply,

and manage supply and demand together

Water Quality:Evaluated 4 Case Study Rivers for Dissolved Oxygen

Select Watersheds Simulate DO: Existing GA DOSAG Models

• All climate trends suggest water temperature is likely to increase.– From < 0.5oF to almost 3oF.

• Changes in dissolved oxygen were estimated as a function of changing temperatures and changing low flows– D.O. reductions could range from ~0 to -1.4 mg/l during low flow

(Ref: State standards: 4 – 5 mg/l)• Could impair aquatic habitat• Could affect effluent standards

Water Quality Modeling Results: Water Temperature and Dissolved Oxygen

Flooding:Evaluated 2 Case Study Watersheds

Land UseFlint River Watershed268 sq. mi.

Yellow River Watershed127 sq. mi.

Residential 35% 60%

Agriculture 14% 1%

Commercial/ Industrial 8% 18%

Forest 24% 8%

Other 18% 13%

Projected Percent Changes in ARI Depths

• Floods that occur every 5, 10, and 25 years will likely intensify• This is true for wet and dry scenarios (rainfall can be

redistributed):

• Important to consider this in bridge, culvert, channel design.• Green infrastructure could help attenuate some peak flows.

Hot/Dry Warm/Wet

Rainfall Depth + 4% to + 12% + 1% to +7%

Peak Streamflow + 6% to + 11% + 2% to +7%

Infrastructure and Adaptation

Water Facilities Risk Scorecard Example: Wastewater Treatment Plants

19

Example of Adaptation Recommendations:Wastewater Treatment Plants

Example of Adaptation Recommendations:Water Treatment Plants

Conclusions and Recommendations

Key Findings• Water Supply:

– Drought severity will likely increase.– Test case reservoir yield could decrease by 10% or increase by up to

30%.– Climate-Influenced Demands will likely increase.– Each utility should manage supply and demand together, based on

their own unique risks.

• Low Flows, Water Quality, and Drought Severity: – More sensitive to temperature than to precipitation– Most scenarios indicate a worsening of these conditions

• Flood Intensity will likely increase, and infrastructure designs should consider this likelihood

23

Near Term Recommendations• Establish climate tracking protocols and identify trigger

levels for adaptive measures.• Incorporate preemptive adaptation measures

– Drought Management: Understand water supply risk at each source, and manage supply and demand conjunctively

– Green infrastructure:• Help attenuate high flows• Help attenuate pollutant loads• Potentially help regulate baseflow

• Consider recommendations from study when updating local master plans

QUESTIONS?

Utility Climate Resiliency Study�OutlineGoals of Utility Climate Resiliency StudyPossible Future Climate ConditionsFuture Climate Scenarios: Annual TemperatureFuture Climate Scenarios: Annual PrecipitationMethods and FindingsAnalysis of Water Demands:�As a function of Policy, Economics, and ClimateWater Demand: �Sensitivity to Climate via Multivariate RegressionLong Term Potential Impacts of Climate Variability:�Per Capita Water Use (by 2050)*Water Supply: �Evaluated Firm Yield of 5 Small/Midsize ReservoirsFirm Yield In Case Study ReservoirsWater Quality:� Evaluated 4 Case Study Rivers for Dissolved OxygenWater Quality Modeling Results: �Water Temperature and Dissolved OxygenFlooding:�Evaluated 2 Case Study Watersheds�Projected Percent Changes in ARI DepthsInfrastructure and AdaptationWater Facilities Risk Scorecard Example: �Wastewater Treatment Plants Example of Adaptation Recommendations:�Wastewater Treatment PlantsExample of Adaptation Recommendations:�Water Treatment PlantsConclusions and RecommendationsKey FindingsNear Term RecommendationsQuestions?