SWAT v. BayFAST: An Inter-model Comparison

Rashmit Arora

What is BayFAST?

• The Bay Facility Assessment Scenario Tool (BayFAST) is a web-based nitrogen, phosphorus and sediment load estimator that is intended to streamline environmental planning

• Users specify the boundaries of a parcel, and then select BMPs to apply on that parcel

Inter-model Comparison Scenarios

• 2012 Baseline

• Watershed Implementation Plans (WIP, Bay program version)

• WIP, CNS SWAT version

BMP list• DryPonds

• EandS

• EffNutMan

• ExtDryPonds

• Filter

• ForestBuffers

• ForestBuffersTrp

• ForestBufUrban

• ForHarvestBMP

• GrassBuffers

• GrassBuffersTRP

• HorsePasMan

• ImpSurRed

• Infiltration

• LaggonCovers

• LandRetireHyo

• LandRetirePas

• MortalityComp

• NonUrbStrmRest

• PoultryInjection

• PoultryPhytase

• PrecRotGrazing

• Septic

• StreetSweep

• SwinePhytase

• TreePlant

• UpPrecIntRotGraze

• UrbanNMPlan

• UrbanTreePlant

• UrbGrassBuffers

• UrbStrmRest

• WetPondWetland

• AbanMineRec

• Alum

• AWMS

• BarnRunoffCont

• CaptureReuse

• CarSeqAltCrop

• ComCovCrop

• ConPlan

• ConserveTillTotAcres

• ContinuousNT

• CoverCropEOW

• DirtGravelDSA

▪ BMPs in CNS SWAT scenario▪ BMPs in CNS SWAT not

available in BayFAST▪ BMPs in Bay program WIP

scenario▪ BMPS in Bay program WIP not

available in BayFAST

SWAT vs. BayFAST

Nutrient TMDL CNS SWAT WIPBayFAST WIP, CNS SWAT

Iteration BayFAST WIP, Bay Iteration

Total N 25.0 12.0 11.0 20.9

Total P 25.0 15.0 0.5 16.6

Sediment 30.0 41.0 12.1 24.5

Conewago Creek

*all numerical values are percentage reductions in the loads delivered to the Bay

Nutrient TMDL CNS SWAT WIPBayFAST WIP, CNS SWAT

Iteration BayFAST WIP, Bay Iteration

Total N 25 25.6 11.0 24.3

Total P 25 12.2 3.9 20.4

Sediment 30 23.3 8.6 24.7

Mahantango Creek

SWAT vs. BayFAST

*all numerical values are percentage reductions in the loads delivered to the Bay

Animal heavy use areas

• Amish Farm Study

– The tests took place over a period of two years

– Saw various configurations of filtration systems employed in order to abate runoffs

– 35 kg of phosphorous entered the treatment system over the first year, followed by a lesser load of 12.6 kg over the second year

→ The detention basin, paired with a flow control structure, removed a tremendous amount of phosphorous -16kg over the two years.

→ The slag filters removed 4.7 kg of phosphorous over the two years

Land Use Loads (sorted for P)

Sector Landuse NLoadDEL (lbs) PLoadDEL (lbs) SLoadDEL (lbs)

Agriculture animal feeding operations 42808.6 2374.9 10089.6

Agriculture lowtill with manure 169027.4 1079.7 1119117

Agriculture concentrated animal feeding operations 12588.1 698.4 2975.3

Agriculture pasture 2527.5 512.2 52078.2

Urban regulated impervious developed 33337.3 438 349299.2

Sector Landuse NLoadDEL (lbs) PLoadDEL (lbs) SLoadDEL (lbs)

Agriculture animal feeding operations 121030 7412.7 44500.7

Agriculture lowtill with manure 377463.8 4080.5 5721761

Agriculture hightill with manure 236719.9 1813.2 4712940

Urban nonregulated extractive 48134.1 1373.6 2387112

Agriculture nursery 29965.7 1334.7 63530.7

Conewago Creek

Mahantango Creek

Animal BMP Scenarios

• 2012 Baseline

• 100% Animal BMPs on AFOs and CAFOs

• 50% Animal BMP, improved WIP (reduced agricultural BMPs)

• 50% Animal BMP, improved WIP (reduced urban BMPs)

100% Animal BMP ScenariosBMP Watershed N (%) P (%) Sed (%) Cost ($)

Loafing Lot Management Conewago 1.9 8.1 0.2 $57,093

Loafing Lot Management Mahantango 1.9 7.3 0.1 $145,650

Loafing Lot Management Spring Creek 0.3 1.1 0.3 $197,315

BMP Watershed N (%) P (%) Sed (%) Cost ($)

Barnyard Runoff Control Conewago 1.9 8.1 0.2 $13,605

Barnyard Runoff Control Mahantango 1.9 7.3 0.1 $34,697

Barnyard Runoff Control Spring Creek 0.3 1.1 0.3 $47,019

BMP Watershed N (%) P (%) Sed (%) Cost ($)

AWMS Livestock Conewago 1.9 7.5 0 $77,301,883

AWMS Livestock Mahantango 1.5 4.9 0 $10,153,555

AWMS Livestock Spring Creek 1.3 4.4 0 $11,103,814

BMP Watershed N (%) P (%) Sed (%) Cost ($)

AWMS Poultry Conewago 4.4 25.2 0 $7,444,525

AWMS Poultry Mahantango 6 23.8 0 $1,893,987

AWMS Poultry Spring Creek 0 0 0 $157,604

Cost Effectiveness Tables

Nitrogen Phosphorous Sediment

BMPCost Effectiveness

($/lb reduced) RankCost Effectiveness

($/lb reduced) RankCost Effectiveness

($/lb reduced) Rank

Conservation Tillage $0.00 1 $0.00 1 $0.00 1

Continuous No-Till $0.00 2 $0.00 2 $0.00 2

Carbon Sequestration and Alternative Crops $66.76 3 $38.02 5 $46.64 6

Conservation Plans - High-till $83.66 4 $20.88 3 $15.01 4

Conservation Plans -Pasture $133.86 5 $31.32 4 $26.81 5

Water Control Structures $181.61 6 - 76 - 76

Ammonia Emissions Reduction - Biofilters $198.70 7 - 43 - 40

Conservation Plans - All Hay $223.10 8 $62.63 6 $46.91 8

Conservation Plans - Low-till $223.10 9 $62.63 7 $46.91 9

Ammonia Emissions Reduction - Alum $238.44 10 #VALUE! 42 #VALUE! 39

50%, Improved WIP Scenario

N P S Cost

20.9 16.6 24.5 $9,778,673

Cost Induced

$939,148

N P Sed Cost

23.7 26.7 24.5 9,699,967

N P Sed Cost

24.3 27.4 25 9,702,543

Bay WIP 50% more AWMS-P

50% more AWMS-P, reduced Alum, AWMS-L

50% more AWMS-P, reduced Dry Extended Ponds

Mahantango Creek

N P S Cost

23.2 26.9 24.5 $10,717,821

Lessons learned

• Approach planning/modeling with caution, understand how different models function and where their biases lie

• Rethink WIPs in terms of cost effectiveness of BMPs

• Increased focus on animal heavy use areas