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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
Wat
er S
uppl
yW
ithd
raw
als
Eva
pora
tive
Los
sF
rom
Irr
igat
ion
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
sF
rom
Irr
igat
ion
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
2.5
3
1 2 3 4 5 6 7 8 9 10 11 12
Month
Wat
er D
epth
(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
2
2.5
0 2 4 6 8 10 12 14
Month
Net
Wat
er O
utF
low
(ft
)
Cranberry Wetland Difference
Cranberry Sub-Model
-1
-0.5
0
0.5
1
1.5
0 2 4 6 8 10 12 14
Month
Net
Wat
er O
utF
low
(ft
)
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)
0.0%
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
ven
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
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
0 2 4 6 8 10 12 14
Month
Nat
ura
l F
low
(cf
sm)
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