Boise River Total Phosphorus Mass Balance Model Ben Cope EPA - - PowerPoint PPT Presentation

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Dec 11, 2023 428 likes •576 views

Boise River Total Phosphorus Mass Balance Model Ben Cope EPA Region 10 Office of Environmental Assessment Impetus: City of Boise Offset Project Adapted from earlier CH2M Hill model Excel spreadsheetsimple Removed TMDL

SLIDE 1

Boise River

Total Phosphorus Mass Balance Model

Ben Cope EPA Region 10 Office of Environmental Assessment

SLIDE 2

Impetus: City of Boise Offset Project
Adapted from earlier CH2M Hill model

– Excel spreadsheet…simple – Removed TMDL allocation calculators – IDEQ review of data-to-model accuracy

Mainstem Boise River only

– Follows south channel at Eagle Island

Mass balance of total phosphorus

– Assumes no loss due to instream processes – Steady state – snapshot in time

Two periods analyzed

– July 2001 – low flow (approx. 30Q10) – August 2000 – higher, more typical summer flow

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New York, Ridenbough, Settler’s, Boise City Canal, Thurman Mill New Dry Creek Phyllis, Eureka Canyon, Caldwell High Line Riverside Sebree Eureka , Lower Center Point Island High Line, McConnel Island Boise Lander WWTP West Boise WWTP Thurmon 15 Mile, Middleton WWTP, Star Feeder, Mill Slough, Star WWTP, Mason Drain Hartley (Combined) Indian Creek (includes Nampa WWTP) Caldwell WWTP Conway Gulch, Dixie Drain Boise River at Boise Boise River at Parma

Mainstem Inflows and Diversions

Groundwater (distributed inflow from Caldwell to Parma) North Channel Routing

These are flows >20 cfs in July 2001 Total number of boundary inputs = 75

SLIDE 5

Development Process

Selection of time frames
Input data review (with IDEQ)
Flow evaluation
Total Phosphorus evaluation
Model application/scenarios
Documentation

SLIDE 6

Mainstem Flow – July 2001

500 1000 1500 2000 2500 3000 3500 0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0 45.0 50.0 55.0 60.0 65.0 70.0 75.0 Flow (cfs) River Mile

Mass Balance Estimate and Measured Instream Flow Boise River on July 12, 2001

Model with GW Measurement Mass Balance Model - Calculated Flow

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Mainstem Flow – August 2000

500 1000 1500 2000 2500 3000 3500 4000 4500 0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0 45.0 50.0 55.0 60.0 65.0 70.0 75.0 Flow (cfs) River Mile

Mass Balance Estimate and Measured Instream Flow Boise River on August 15, 2000

Model with GW Measurement Mass Balance Model - Calculated Flow

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Total Phosphorus – July 2001

0.10

0.00 0.10 0.20 0.30 0.40 0.50 0.60 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 Total Phosphorus River Mile

Estimated vs Measured Instream Phosphorus Boise River: July 2001

Instream Measurement Mass Balance Model

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Total Phosphorus – August 2000

0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 Total Phosphorus River Mile

Estimated vs Measured Instream Phosphorus Boise River: August 2000

Instream Measurement Mass Balance Model

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Application City of Boise Offset Scenarios

0.342 0.316 0.020 0.304 0.263

0.000 0.100 0.200 0.300 0.400 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 Total Phosphorus River Mile

Predicted Instream Phosphorus Boise River: July 2001 Conditions Buildout Effluent Flow (39 mgd)

Existing Condition No Offset - B45 No Offset - B70 Offset - B225 Offset - B350

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Key Assumptions/Uncertainties

Groundwater flow and TP concentration

– Uniform flow in lower reach – Concentration set at mean drain concentration

Consistent with USGS sampling mean but limited samples
Drain TP data is “patchy”

– Synoptic sampling by USGS will help ground truth

Offset assumption: TP removed from mainstem by

diversions does not return to mainstem

– How much comes back to mainstem: unknown – Thorny problem in past TMDL efforts

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Documentation

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Questions?

Acknowledgements: Sherrill Doran, CH2M Hill Darcy Sharp, IDEQ Susan Beattie, IDEQ Bill Stewart, EPA