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Plymouth Carver Aquifer Area Water Budgets Nigel Pickering Senior Engineer and Modeler Charles River Watershed Association

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Presentation on theme: "Plymouth Carver Aquifer Area Water Budgets Nigel Pickering Senior Engineer and Modeler Charles River Watershed Association"— Presentation transcript:

1 Plymouth Carver Aquifer Area Water Budgets Nigel Pickering Senior Engineer and Modeler Charles River Watershed Association

2 PCAA Water Budgets Project Structure Funding & Project Management –EOEEA Data Collection & Processing –Fuss & ONiell –MassGIS Analysis & Reports –CRWA Collaborators –Communities –MassDEP –EPA –USGS

3 PCAA Project Location

4 Why Water Budgets? Assess human impacts on streamflow Need a balanced, standardized approach Results should help prioritize remediation Educate & promote sustainable water use

5 Water Budget Inputs and Outputs

6 Water Budget Components (units are mgd) Impact = SD – SW + (WS – WW – IRR – RIA + GD – GW) * SFAC Impact= total subbasin gain or loss SD= wastewater discharge to surface water SW= withdrawal from surface water WS= water supply gain WW= wastewater loss including infiltration from groundwater IRR= evaporation loss from irrigation RIA= recharge loss from impervious area GD= wastewater discharge to ground water GW= withdrawal from ground water SFAC= storage factor (0.9 – 1.1)

7 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

8 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

9 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

10 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

11 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)

12 Cranberry Sub-Model



15 Water Transfers and Irrigation 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

16 Piped Distribution Systems Water supply only Sewer only Water & sewer

17 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

18 Effective Impervious Area (EIA)

19 Natural Streamflow Estimation QN m = (Int + Area AC * S&G SGC * Prec PC * Elev EC * Slope SC ) / Area m= month (1=Jan, 2=Feb, etc.) QN m = natural flow in month m (cfsm) Int = Intercept coefficient (-) Area = subbasin area (mi 2 ), 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: –QN 4 = 3.0-3.7 cfsm –QN 9 = 0.1-0.7 cfsm

20 PCAA Natural Streamflows

21 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

22 PCAA Water Budgets Report Summarizes subbasin results within the aquifer boundary Outlines general mitigation measures

23 Impact Maps AprilSeptember

24 Impact Table for September SubbasinArea (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 (%) 210710.430.01-0.860.020.010.00 -0.840.18-474.60 240030.413.44-0.330.000.01-0.010.00-0.340.15-225.85 210721.640.00-0.780.000.01-0.010.00-0.780.65-119.93 210592.252.07-0.790.020.09-0.03-0.02-0.720.92-78.91 210656.014.58- 210833.871.20-0.330.030.07-0.08-0.01-0.331.31-24.97 2107514.922.85-0.220.362.69-4.13-0.15-1.456.02-24.11 210857.761.87-0.520.040.14-0.25-0.05-0.632.78-22.73 2400710.370.71-0.980.220.24-0.06-0.03-0.613.98-15.35 210819.211.16-0.910.141.18-0.85-0.03-0.483.31-14.37 210636.5712.88- 240018.414.69-0.570.090.45-0.21-0.13-0.373.13-11.71 240049.811.40-0.590.31 -0.33-0.05-0.353.71-9.42 21060-P4.879.25-0.480.200.46-0.12-0.17-0.122.06-6.01 240170.620.050.00 0.01-0.010.00 0.16-2.92 240066.680.460.000.100.03-0.12- 210730.920.060.00 0.01-0.010.00 0.360.13 240151.640. 0.380.55 240132.076.630.00 0.12-0.07- 24005-B4.468.410.000.100.23-0.15- 25048-P9.322.39-0.010.360.05-0.13- 21058-P3.521.440.000.110.02-0.03- 21054-P0.441.120.00 0.02- 24012-P41.851.87-1.182.560.98-0.75-0.291.3317.027.80 210893.964.06- 2400920.461.34- 210670.759. 21056-P1.964.660.000.090.07-0.02- 210795.512.62- 210870.773.030.00 0.11-0.05- 21053-P0.301.260.00 0.04- 240141.213.100.00 0.12-0.03- 24011-AP1.634.590.000.040.15-0.05- 24005-A4.175.04-0.621.040.25-0.09-0.040.540.9656.62

25 Remediation Options Water Conservation Withdrawal Optimization Stormwater Recharge Wastewater Recharge and Reuse Water Transfers and Trading

26 Water Budgets Implications for PCAA Identifies impacts by subbasin Roadmap for protection and/or remediation Sets up framework for flow trading

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