Plymouth Carver Aquifer Area Water Budgets

S ub b as in W aterB ud get

S tr eam f lo w O u tS tr eam f lo w I n

W as tew a te r D isc h a rg e

Wastew

ater Loss,

Including I/I

Recharge L

oss From

Impervious C

over

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W a te r S u p p ly In p u t

Nigel Pickering

Senior Engineer and Modeler

Charles River Watershed Association

www.charlesriver.org

PCAA Water BudgetsProject Structure

• Funding & Project Management– EOEEA

• Data Collection & Processing– Fuss & O’Niell– MassGIS

• Analysis & Reports– CRWA

• Collaborators– Communities– MassDEP– EPA– USGS

PCAA Project

Location

Why Water Budgets?

• Assess human impacts on streamflow

• Need a balanced, standardized approach

• Results should help prioritize remediation

• Educate & promote sustainable water use

Water Budget Inputs and Outputs

S ub b as in W aterB ud get

S tr eam f lo w O u tS tr eam f lo w I n

W as tew a te r D isc h a rg e

Wastew

ater Loss,

Including I/I

Recharge L

oss From

Impervious C

over

Wat

er S

uppl

yW

ithd

raw

als

Eva

pora

tive

Los

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rom

Irr

igat

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W a te r S u p p ly In p u t

Water Budget Components(units are mgd)

Impact = SD – SW + (WS – WW – IRR – RIA + GD – GW) * SFAC

Impact = total subbasin gain or lossSD = wastewater discharge to surface waterSW = withdrawal from surface waterWS = water supply gainWW = wastewater loss including infiltration from groundwaterIRR = evaporation loss from irrigationRIA = recharge loss from impervious areaGD = wastewater discharge to ground waterGW = withdrawal from ground waterSFAC = storage factor (0.9 – 1.1)

Water Budget Examples

• PWS, septic, no IA– water in - no water out = net gain

• PWS, sewer, no IA– water in - more water out (incl. I/I) = net loss

• Water withdrawal, no PWS, no WW, no IA– no water in - water out = net loss

• Wastewater discharge, no PWS, no WW, no IA– water in – no water out = net gain

• No PWS, no WW, large IA– no water in - water out = net loss

Withdrawals and Discharges

• Monthly flows for 2000-2004– filled-in if necessary

• Average monthly flow computed

• River withdrawals & discharges directly from sub-basin

• Well withdrawals converted to stream depletion using StrmDepl (USGS)

• Well withdrawals distributed over subbasins with zone of contribution

Cranberry Bog Impacts• Reported system areas for 2000-2004

– filled-in if necessary

• System area distributed over number of number of withdrawal points

• Monthly sub-model developed for 1-ac of cranberry– monthly inputs/outputs in ac-ft of water

• Converted to monthly point volumes (mgd) using annual area and monthly factors

Cranberry Sub-Model

• Water balance of typical cranberry farm

• Assumed calendar and amounts for water-related events

• Water moved in and out for harvesting, frost-damage control, and weed control

• Water used for irrigation in the growing season--small for “average” year

• Net water use expressed relative to natural landscape i.e. wetland

Cranberry Sub-Model• Calendar

– May to Sep-growing season• crop ET coefficient = 0.66• irrigation at 1”/wk when dry

– Oct-harvest• field flooded (1.5 ft) and drained (1.5 ft)

– Nov & Dec-freeze protection• Add water (1.0 ft then further 0.7 ft)

– Mar-drain and flood• Release (2.0 ft) and add water (2.0 ft)

– early May-drain field• Release water (2.0 ft)

Cranberry Sub-Model

0

0.5

1

1.5

2

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1 2 3 4 5 6 7 8 9 10 11 12

Month

Wat

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(ft

)

Inflow Outflow Cranberry Level Wetland Level

Total withdrawals = 5.2 ft/yr

Cranberry Sub-Model

-1.5

-1

-0.5

0

0.5

1

1.5

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Month

Net

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(ft

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Cranberry Wetland Difference

Cranberry Sub-Model

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-0.5

0

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Month

Net

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(ft

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Cranberry Wetland Difference

Wetland Net Outflow = 1.00 ft/yrCranberry Net Outflow = 1.86 ft/yr

Net Gain = 0.86 ft/yr

Water Transfers and Irrigation

Sewer SepticPublic water +WS - WW - IRR +WS - IRRPrivate well - WW - IRR - IRR

WW = wastewater including I/IIRR = irrigation

WS = public water supply

• Subbasin transfers computed using system unit flows with people and areas

• People and areas from distribution system maps and new MassGIS population density map

• Monthly irrigation loss computed as:– 75% of (monthly use - winter use)– Applied to both public/private irrigation areas

Piped Distribution

Systems

• Water supply only

• Sewer only

• Water & sewer

Effective Impervious Area (EIA)

• Loss assumed proportional to EIA– 10% EIA 10% reduction in streamflow

• Subbasin TIA from new MassGIS IA grid

• Subbasin EIA computed from TIA as:Effectiveness (%) = -0.214+1.429*TIA (0 to 100)

EIA (%) = Effectiveness (%) * TIA (%) / 100

Effective Impervious Area (EIA)

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20.0%

40.0%

60.0%

80.0%

100.0%

0.0% 20.0% 40.0% 60.0% 80.0% 100.0%

TIA (%)

Eff

ecti

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ess

or

EIA

(%

)

Eff EIA

0.0%

10.0%

20.0%

30.0%

40.0%

50.0%

60.0%

70.0%

LDR MDR HDR MFR INDL COMM

EIA

(%

)

Natural Streamflow EstimationQNm = (Int + AreaAC * S&GSGC * PrecPC * ElevEC * SlopeSC) / Area

m= month (1=Jan, 2=Feb, etc.)

QNm = natural flow in month m (cfsm)

Int = Intercept coefficient (-)

Area = subbasin area (mi2), AC = Area coefficient

S&G = percent sand and gravel (%), SGC = S&G coefficient

Prec = annual precip. (in/yr) from 30-s PRIZM grids (1970-2000), PC = Prec coefficient

Elev = avg. subbasin elevation (ft) from 30-m DEMs, EC = Elev coefficient

Slope = average subbasin slope (%), SG = Slope coefficient

• Based on 23 USGS index flow gages (Armstrong et al., 2003)• No flow gages in PCAA or Cape Cod• For PCAA, the range of values is:

– QN4 = 3.0-3.7 cfsm

– QN9 = 0.1-0.7 cfsm

PCAA Natural Streamflows

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Water Budget Calculations

Impact (mgd) = SD – SW + (WS–WW–IRR–RIA+GD–GW)*SFAC

Impact (cfsm) = Impact (mgd) * 1.547 cfs/mgd / Area (mi2)

Impact (%) = Impact (cfsm) / QN (cfsm) * 100

PCAA Water Budgets Report

• Summarizes subbasin results within the aquifer boundary

• Outlines general mitigation measures

Impact MapsApril September

Impact Table for

September

Subbasin Area (mi2) EIA (%)Withdrawals

(MGD)Discharges

(MGD)

Transfers Via Dist. System (MGD)

Irrigation Losses (MGD)

EIA Recharge

Losses (MGD)

Total Vol. Impact on NS (MGD)

Natural Stream-flow (NS) (MGD)

Relative Impact on

NS (%)

21071 0.43 0.01 -0.86 0.02 0.01 0.00 0.00 -0.84 0.18 -474.60

24003 0.41 3.44 -0.33 0.00 0.01 -0.01 0.00 -0.34 0.15 -225.85

21072 1.64 0.00 -0.78 0.00 0.01 -0.01 0.00 -0.78 0.65 -119.93

21059 2.25 2.07 -0.79 0.02 0.09 -0.03 -0.02 -0.72 0.92 -78.91

21065 6.01 4.58 -1.17 0.11 0.50 -0.23 -0.11 -0.90 2.55 -35.31

21083 3.87 1.20 -0.33 0.03 0.07 -0.08 -0.01 -0.33 1.31 -24.97

21075 14.92 2.85 -0.22 0.36 2.69 -4.13 -0.15 -1.45 6.02 -24.11

21085 7.76 1.87 -0.52 0.04 0.14 -0.25 -0.05 -0.63 2.78 -22.73

24007 10.37 0.71 -0.98 0.22 0.24 -0.06 -0.03 -0.61 3.98 -15.35

21081 9.21 1.16 -0.91 0.14 1.18 -0.85 -0.03 -0.48 3.31 -14.37

21063 6.57 12.88 -0.25 0.00 0.69 -0.46 -0.32 -0.33 2.79 -11.96

24001 8.41 4.69 -0.57 0.09 0.45 -0.21 -0.13 -0.37 3.13 -11.71

24004 9.81 1.40 -0.59 0.31 0.31 -0.33 -0.05 -0.35 3.71 -9.42

21060-P 4.87 9.25 -0.48 0.20 0.46 -0.12 -0.17 -0.12 2.06 -6.01

24017 0.62 0.05 0.00 0.00 0.01 -0.01 0.00 0.00 0.16 -2.92

24006 6.68 0.46 0.00 0.10 0.03 -0.12 -0.01 0.00 2.54 -0.07

21073 0.92 0.06 0.00 0.00 0.01 -0.01 0.00 0.00 0.36 0.13

24015 1.64 0.18 0.00 0.01 0.02 -0.03 0.00 0.00 0.38 0.55

24013 2.07 6.63 0.00 0.00 0.12 -0.07 -0.04 0.01 0.64 1.91

24005-B 4.46 8.41 0.00 0.10 0.23 -0.15 -0.12 0.07 1.62 4.04

25048-P 9.32 2.39 -0.01 0.36 0.05 -0.13 -0.08 0.18 3.70 4.95

21058-P 3.52 1.44 0.00 0.11 0.02 -0.03 -0.02 0.08 1.37 5.67

21054-P 0.44 1.12 0.00 0.00 0.02 -0.01 0.00 0.01 0.16 7.65

24012-P 41.85 1.87 -1.18 2.56 0.98 -0.75 -0.29 1.33 17.02 7.80

21089 3.96 4.06 -0.09 0.00 0.51 -0.26 -0.05 0.11 1.31 8.80

24009 20.46 1.34 -0.03 1.18 0.09 -0.09 -0.10 1.07 8.16 13.06

21067 0.75 9.15 0.00 0.01 0.07 -0.03 -0.02 0.03 0.26 13.18

21056-P 1.96 4.66 0.00 0.09 0.07 -0.02 -0.03 0.11 0.79 13.84

21079 5.51 2.62 -0.23 0.17 0.85 -0.42 -0.05 0.32 1.95 16.19

21087 0.77 3.03 0.00 0.00 0.11 -0.05 -0.01 0.05 0.26 18.03

21053-P 0.30 1.26 0.00 0.00 0.04 -0.01 0.00 0.03 0.12 21.06

24014 1.21 3.10 0.00 0.00 0.12 -0.03 -0.01 0.07 0.34 21.62

24011-AP 1.63 4.59 0.00 0.04 0.15 -0.05 -0.02 0.12 0.38 32.65

24005-A 4.17 5.04 -0.62 1.04 0.25 -0.09 -0.04 0.54 0.96 56.62

Remediation Options

• Water Conservation

• Withdrawal Optimization

• Stormwater Recharge

• Wastewater Recharge and Reuse

• Water Transfers and Trading

Water Budgets ─ Implications for PCAA

• Identifies impacts by subbasin

• Roadmap for protection and/or remediation

• Sets up framework for flow trading