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City of Raleigh briefing for Jordan Lake Partnership

October 24, 2014

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2

El. 251.5

El. 236.5

Flood Storage

Sed. S.

Water Quality

Pool

Water Supply

Pool

20 BG 14.7 BG

8.2 BG

Falls Lake Storage Profile

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Falls Lake

Clayton Gage

Illustration of Water Supply Usage Impact on Clayton Flow Target

Illustration of Water Supply Usage Impact on Clayton Flow Target

Water Supply Pool

Water Quality Pool

Raleigh Service

Area

Flow Target184 cfs Nov – Mar254 cfs Apr – Oct

NR WWTP

11

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Reallocate 4.1 BG of WQ Pool

(20.5% of existing WQ Pool) to WS Pool

El. 251.5

El. 236.5

Flood Storage

Sed. S.

Water Quality

Pool

Water Supply

Pool

Reallocation Alternative

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Raleigh Quarry Storage with Neuse River Intake below Richland Creek as a BackupRaleigh Quarry Storage with Neuse River Intake below Richland Creek as a Backup

5

EMJ WTP

Raleigh Quarry

Falls Lake

16

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Raleigh Quarry50-yr Marginal Yield for Raleigh Quarry

(and Neuse River Intake when indicated)

0

2

4

6

8

10

12

14

16

18

0 BG 1 BG 2 BG 3 BG 4 BG 5 BG 6 BG 7 BG 8 BG 9 BG

Raleigh Quarry Usable Volume

Op

era

tio

na

l 50

-ye

ar

Yie

ld -

MG

D

No Direct transfer from Neuse River to EMJ, 50 mgd recharge rate

Richland Ck backup intake (@18.5 mgd), 50 mgd quarry recharge

Purpose and Need

Raleigh Quarry Storage (with Neuse River Intake below Richland Creek as a Backup)

Estimated current volume

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River Intake Above Neuse River WWTP River Intake Above Neuse River WWTP

7

Falls Lake

Lake Benson

Raleigh Service

Area

Lake Wheeler

NR WWTP

DE Benton WTP

EMJ WTP

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River Intake Above Neuse River WWTP

Area shaded in green shows potential extent of water supply watershed overlay

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Falls Lake EFDC ModelFalls Lake EFDC Model

Developed by NCDENR DWR to aid in developing nutrient management strategy

Completed in 2009 under guidance of Falls Lake Technical Advisory Committee

Simulating Chl-a concentrations was key purpose Chl-a goal:

Less than 40 µg/L 90% of the time

Focused primarily on nutrientinputs from tributaries

Developed by NCDENR DWR to aid in developing nutrient management strategy

Completed in 2009 under guidance of Falls Lake Technical Advisory Committee

Simulating Chl-a concentrations was key purpose Chl-a goal:

Less than 40 µg/L 90% of the time

Focused primarily on nutrientinputs from tributaries

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Simulation ScenariosSimulation Scenarios

Hydrology

Historical Outflow

Max WS – Current

Allocation

Max WS – A.4

Allocation

Inflow Chl-a Concentratio

n

Unmodified Base Model

Inflow Chl-a = 10 µg/L

Nutrient Reductions

No Nutrient

Reductions

40% N 77% P

Reductions

12 Total Simulation Scenarios

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Chl-a Exceedance FrequencyChl-a Exceedance Frequency

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Unmodified Chl-a, Nutrient ReductionsUnmodified Chl-a, Nutrient Reductions

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The dotted grey line above represents simulated historical conditions without nutrient reductions in place, with the grey stars illustrating the observed Chl-a concentrations used for model calibration. Historical withdrawal, current allocation, and A4 allocation lines reflect implementation of 40%N / 77%P reductions.

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The grey band illustrates the root mean squared error from model calibration efforts. Measured Chl-a concentrations were generally within 17.89 µg/L of the concentration simulated for that point in time.

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Other Options?Other Options?

Reclaimed Water as a Source Water

Jordan Lake Allocation

Reclaimed Water as a Source Water

Jordan Lake Allocation