Modeling Hydrodynamics and Water Quality for Wachusett Reservoir

Modeling Hydrodynamics and Water Quality for Wachusett Reservoir John Tobiason, David Ahlfeld, Mary Serdakowski, Christina Stauber University of Massachusetts, Amherst Department of Civil and Environmental Engineering conducted for MA Department of Conservation and Recreation (DCR) Division of Water Supply Protection 5th Annual Water Resources Research Conference UMass-Amherst, April 8, 2008 Acknowledgements Funding: • MA Department of Conservation & Recreation – Division of Water Supply Protection – Consumers → MWRA → DCR Essential Support: • DCR staff – Patricia Austin, Bill Pula, many others! • MA Water Resources Authority (MWRA) • UMass Faculty Colleagues – David Reckhow, Paula Rees, Sharon Long, Jim Edzwald, Jim Male Real Work! • UMass graduate students (1995-2007) – Michael Hayes, Evelyn Wolfram, Elisa Garvey, Diane Mas, Alejandro Joaquin, Matt Kennedy, Meg Roberts, Rebecca Pease, Dan Buttrick, Thomas Matthews, Mary Serdakowski, Christina Stauber DCR/MWRA System

N DCR/MWRA Reservoir System

Quabbin Aqueduct

Chicopee Valley Aqueduct (CVA) DCR/MWRA System • Management – DCR – watersheds & reservoirs – MWRA – transmission, treatment, bulk supply • Source Reservoirs (for about 2.5 million population) – Quabbin – west central MA – Wachusett – central MA • Treatment – Quabbin: free chlorination only, add UV in future – Wachusett: ozonation (7/05) & chloramination only, UV in future – pH and alkalinity adjustment – no coagulation/filtration; no removal of NOM/DBP precursors • Water Quality Management Strategies – Watershed protection: best management practices; land use – Quabbin to Wachusett Transfer operation System Quantity

Item Quabbin Reservoir Wachusett Reservoir Unit Capacity 412 65 BG

Watershed Area 187 117 mi2 Average Depth 52 51 feet Mean Hydraulic 5.9 0.6 years Residence time Average Discharge 125 220 MGD Discharge Range 0 - 300 170 - 325 MGD Outlet Swift River Nashua River Destination Wachusett and CVA Metro-Boston System Quality

Item Quabbin Reservoir Wachusett Reservoir Unit Conductivity 40 - 50 70 - 110 μS/cm Phosphorus <5 - 9 <5 - 18 μg P/L Ammonia <5 - 21 <5 - 26 μg N/L Nitrate <5 - 21 15 - 130 μg N/L Algae ≤ 900 ≤ 1700 ASU/mL TOC 1.5 - 2.5 1.8 - 3.5 mg/L UV 254 0.015 - 0.030 0.03 - 0.09 cm-1 Trophic State Oligotrophic Oligo-mesotrophic UMass/DCR Project Objectives

Long Term • Maintain field/lab/modeling expertise directed at improved science-based watershed & reservoir management decisions • Working from 1995 to present Shorter Term • Evaluate specific management issues • Verify impact of management practices • Respond to new/developing priority issues Project Structure & Studies • Watershed Process Characterization – Sources/type/amount of natural organic matter (NOM) – Assessment of storm-event based water quality sampling (with AwwaRF) – Tasks: field sampling, water quality analyses, laboratory experiments, modeling • Microbiological Issues – Alternative indicator organisms for source tracking – Assessment of impacts of land use & sanitation changes – Understanding source/occurrence of reservoir coliforms • Reservoir Hydrodynamics and Water Quality Reservoir Modeling & Measurements

Hydrodynamics • Water budget – data needs/ gaps • Water velocities & transport time • Water transfer impacts • 2D CE-QUAL W2 & 3D Fluent CFD model • Developing 3D GEMSS model Water Quality • Coliform • NOM (algae, TOC, DOC, UV254, etc.) • Nutrients (N,P) • Contaminant Spills Quabbin Reservoir Quabbin Reservoir Studies

• Impact of Gull Roosting on Coliforms – Confirmed need for DCR gull harassment to avoid coliform violations [important for filtration waiver] • NOM: Inputs & Transformations – Assessed concentration & character of NOM, relationships between NOM measures, material flux balances Wachusett Reservoir

North Basin

Thomas Basin

South Basin Cosgrove Withdrawal to WTP

Cosgrove Intake Structure

N Wachusett Inputs/Outputs

Stillwater Evaporation Spillway

Nashua River Release

Quinapoxet Precipitation / Wachusett Wachusett Runoff Aqueduct Reservoir

Quabbin Cosgrove Transfer Intake

Minor Tributaries 2004 Inflow Hydrograph

25.0 Quabbin Transfer Stillwater River 20.0 Quinipoxet River ) Direct Precipitation

15.0

10.0 Major Inflows (m^3/s 5.0

0.0 1/1/04 2/1/04 3/3/04 4/3/04 5/4/04 6/4/04 7/5/04 8/5/04 9/5/04 10/6/04 11/6/04 12/7/04 Date 2004 Outflow Hydrograph & WSE

121.0 WSE 25.0 WSE Target 120.5 WSE Calculated Nashua River Cosgrove Aquaduct 20.0 120.0 Wachusett Aquaduct Nashua Spillway 119.5 15.0 119.0

WSE, m 118.5 10.0 118.0 Discharge, cu. m/sec

117.5 5.0 117.0

116.5 0.0 1/1/04 2/1/04 3/3/04 4/3/04 5/4/04 6/4/04 7/5/04 8/5/04 9/5/04 10/6/04 11/6/04 12/7/04

Spillway calibration to 393.5 and 392.5 ft CEQUAL W2 Wachusett Reservoir

North Basin Thomas Basin

South Basin CEQUAL W2 Wachusett Reservoir – Layer Profile 2004 Temperature Profiles

May 4, 2004 July 7, 2004

32 (South Basin) 42 (North Basin) 11 (Thomas Basin) 32 (South Basin) 42 (North Basin) 46 (Cosgrove Intake) 11 (Thomas Basin) 46 (Cosgrove Intake) 0 0

-5 -5

-10 -10

-15 -15

Depth(m) -20

Depth (m) -20

-25 -25 Measured -30 Measured Simulated -30 Simulated -35 010203001020300 1020300102030 -35 0 102030 Temperature (°C) 01020300102030 0102030 Temperature (°C)

11 (Thomas Basin) 32 (South Basin) 42 (North Basin) 46 (Cosgrove Intake) 0

-5

-10 September 30, 2004

-15

Depth (m) -20

-25

-30 Measured Simulated -35 010203001020300 1020300 102030 Temperature (°C) 2004 Conductivity Profiles

May 4, 2004 July 7, 2004

11 (Thomas Basin) 32 (South Basin) 42 (North Basin) 46 (Cosgrove Intake) 11 (Thomas Basin) 32 (South Basin) 42 (North Basin) 46 (Cosgrove Intake) 0 0

-5 -5

-10 -10

-15 -15 Depth(m) -20 Depth (m) -20

-25 Measured -25

-30 Measured Simulated -30 Simulated -35 -35 0 50 100 150 200 0 50 100 150 200 0 50 100 150 200 0 50 100 150 200 0 50 100 150 200 0 50 100 150 200 0 50 100 150 200 0 50 100 150 200

Specific Conductance (uS/cm) Specific Conductance (uS/cm)

11 (Thomas Basin) 32 (South Basin) 42 (North Basin) 46 (Cosgrove Intake) 0 -5 September 30, 2004 -10

-15

Depth (m) -20

-25

-30 Measured Simulated -35 0 50 100 150 200 0 50 100 150 200 0 50 100 150 200 0 50 100 150 200 Specific Conductance (uS/cm) Travel Time vs Stratification Based on Simulation Results (Alejandro Joaquin MSEVE 2001)

70 % of Quabbin transfer water in Cosgrove withdrawals 60

40 50 40 Travel time (days) 30 30 20 20 10

0 0 1 2 3 4 5 6 7 8 9 10111213141516

dTmax (C)

Epilimnion to Hypolimnion Temp Difference Modeling NOM

NOM

SURROGATE:Organic Carbon SURROGATE:

UV 254 Dissolved Particulate

Labile Living (phytoplankton)

Refractory Nonliving (Detritus) Wachusett TOC Calibration: 2001 – 2002 (Dan Buttrick, MS EVE 2005) 3.5

3.0 TOC (CEQUAL) Measured TOC 2.5 L

2.0

1.5 RDOM

Organic carbon, mg C/ mg carbon, Organic 1.0 Algae (CEQUAL) Measured Algae Detritus LDOM 0.5

0.0

5 Transfer, cu. m/secTransfer, cu. 0 1/23/01 5/3/01 8/11/01 11/19/01 2/27/02 6/7/02 9/15/02 WW Pump Station Malfunction Scenarios (Thomas Matthews, MS EVE 2007)

Beaman Pond Brook Cove 50,000 Gallons North Basin 12 Hour Duration

Thomas Basin South Basin

Gates Brook Woodland St Pump Station 180,000 Gallons 12 Hour Duration Fecal Coliform Concentration 8 1E8 CFU/100mL in Spill = 10 CFU/100 mL Coliform Modeling

Coliform Bacteria

Light 1-st Order Settling Decay Induced Decay

System Loss

• Problem: CEQUAL W2 does not include light induced decay when modeling coliform

• Solution: modify Fortran algorithm Coliform Decay

∂(Coliform) = −k (Coliform) ∂t Coliform kColiform = kColiform, temp + kColiform, light + kSettling

(T-20) kColiform,temp = kColiform, 20 θ

(-γz) kColiform, light = a Io e

ksettling = ω/ΔZ Baseline Fecal Coliform Decay Coefficients

CE QUAL W2 Description This Study Parameter Arrhenius temperature rate CGQ10 1.04 multiplier, θ Coliform dark decay at 20°C, k , CG1DK 20 0.75 day-1

CGS Settling rate, ω, m/day 0.29 Proportionality constant relating irradiance-induced decay rate LITDK 0.014 coefficient to irradiance, α, cm2/cal CEQUAL W2 Wachusett Reservoir

North Basin Thomas Basin

South Basin

Spill Input Segment 32 Individual Decay Mechanisms Segment 32, Layer 31 June 18, 2004 Spill 3500

3000 No decay ) Only Light (alpha=0.014 cm2/cal) 2500 Only Settling (w=0.29 m/s) Only Temp (theta=1.04, k20=0.75 1/day) 2000

1500

1000 Coliform (CFU/100mL 500

0 6/18 7/8 7/28 8/17 9/6 9/26 10/16 11/5 11/25 12/15 Date (2004) Baseline Scenario, All Decay Mechanisms Segment 32, Layer 31

June 18, 2004 Spill 30

25 ) All Decays (w=0.29 m/d, alpha=0.014 cm2/cal, k20=0.75 1/day, 20 theta=1.04)

10 Coliform (CFU/100mL 5

0 6/18 6/20 6/22 6/24 6/26 6/28 6/30 7/2 7/4 7/6 7/8 Date (2004)

Peak concentration for first order No evidence of fecal coliform at temperature decay was 78 the Cosgrove Intake CFU/100 ml Individual Decay Mechanisms In-reservoir Profiles

Segment 20 Segment 24 Segment 28 32 (South Basin) Segment 42 Segment 44 46 (Cosgrove Intake) 0

-5

June 19, 2004 -10 -15 (12 hours after beginning of spill) (m)Depth -20

-25 No Decay Light Only Settling -30 Temp Only

-35 0 150000 300000 0 100 200 00.5100.5100.5100.5100.51

32 (South Basin) Segment 20 Segment 24 Segment 28 Segment 42 Segment 44 46 (Cosgrove Intake) 0

-5 June 28, 2004 -10 (10 days after beginning of spill) -15

Depth (m) Depth -20

-25 No Dec ay Light Only Settling -30 Temp Only

-35 0 5000 10000 0 2500 5000 7500 0 5000 0 2000 4000 0501200.51 Individual Decay Mechanisms Cosgrove Intake

No evidence of fecal coliform at the June 18, 2004 Spill Cosgrove Intake if any decay occurs 400 No Decay 350 Only Temp (theta=1.04, k20=0.75 1/day)

) 300 Only Settling (w=0.29 m/s) Only Light (alpha=0.014 cm2/cal) 250

200

150

Coliform (CFU/100mL Coliform 100

0 6/18 7/8 7/28 8/17 9/6 9/26 10/16 11/5 11/25 12/15 Date (2004) Wachusett Reservoir

North Basin

Thomas Basin

South Basin General Wachusett Spill Inputs Vary location, date, wind, temp., magnitude, Quabbin transfer operation (current work of Mary Serdakowski, Christina Stauber) Ex: Rte 140 Bridge, tracer, 12 hr spill, Cosgrove Conc. 0.8 n 0.7 Spring (JD 120) 0.6 Summer (JD 230) 0.5 Fall (JD 319) 0.4 0.3 0.2 0.1 0 Relative Tracer Concentratio Relative -0.1 0 5 10 15 20 25 30 days after spill Summer JDAY 230, 2004 Spill at Seg 7 (Rt. 140) Start at noon until midnight, Quabbin turned off within 12 hours Tracer Concentrations at Cosgrove

3.5 Quabbin OFF (stream temp) 3 Quabbin Reg (stream temp) 2.5

1.5

Relative Concentration Relative 1

0.5

0 0 102030405060 days after spill Thomas Basin: need for 3-D model (Matt Kennedy, MS EVE 2002; Rebecca Pease MS EVE 2003)

Quabbin Transfer

Length: (Thalweg): 2 kilometers (1.25 miles) Width: 200 – 400 meters (650 – 1300 feet) Max. Depth: 16.75 meters (55 feet) CFD Result: Quabbin Transfer

Velocity in m/s

2-meters below surface Quabbin Transfer Tracer Paths Line color is time in days

Quinapoxet Inlet Particle entrainment Tracer Pulse in recirculation regions

Less entrainment in Stillwater Inlet low velocity Tracer Pulse dead space Spill Location Simulations: management action?

0.20

0.18

0.16

0.14 HRT = 12.5 ± 10 days

) 0.12 -1

0.10

E(t) (days E(t) 0.08 0.18 0.06 0.16 0.04 0.14 0.02

0.00 0.12 HRT = 10 ± 8 days

0 7 14 21 28 35 ) -1 Time, t (days) 0.10

0.08 E(t) (days E(t)

1.60 0.06

1.40 0.04

1.20 0.02

0.00 1.00 HRT = 3.5 ± 1 days ) 0 7 14 21 28 35 -1 Time, t (days) 0.80 E(t) (days E(t) 0.60

0.40

0.20 0.12

0.00 HRT = 13 ± 5 days 0.10 0 7 14 21 28 35 Time, t (days) 0.08 ) -1

0.06 E(t) (days E(t)

0.04

0.02

0.00 0 7 14 21 28 35 Time, t (days) SUMMARY

• DCR/UMass collaboration effective at addressing long-term questions and response to emergencies • Value of expertise/institutional knowledge for new/short term issues • Foundation for rational basis for policy making Thank you!