Full Proceedings available at: http://www.extension.org/72795
The revision of USDA-NRCS’s standard for nutrient management coincided with significant assessment of the performance of Phosphorus (P) Indices in the six states that are tied to the Chesapeake Bay watershed. The 64,000 square mile watershed is the focus of unprecedented activity around nutrient management as a result of a 2011 Total Maximum Daily Load for P, nitrogen (N), and sediment under the Clean Water Act. In addition, the state of Maryland had required updates to it’s original P Index, resulting in broad scrutiny by various interest groups. Within this setting, USDA-NRCS funded a multi-state project to help advance the testing and harmonization of P-based management in the Chesapeake region.
Modeling phosphorus runoff in the chesapeake bay region to test the phosphorus index
1. Modeling Phosphorus to Test the
P Index in the Chesapeake Bay Region
Pete Kleinman, D. Beegle, Z. Easton, A. Collick, J.
Weld, Q. Ketterings, K. Czymmek, D. Fuka, T. Veith,
A. Shober, S. Cela, M. Reiter, A. Allen, J. McGrath, R.
Bryant, J. Liu, K. Clark, T. Buda and
M. Amin, T. Basden
5. WE38 – detailed field-scale modeling
https://i.ytimg.com/vi/wx0SJM7FeEc/mqdefault.jpg
http://www.extension.org/sites/default/files/w/4/4a/
Spreading_manure.jpg
• Pre-process SWAT to field-scale
• Every field can have a different set of
practices
• Field specific management scenarios
6. Hydrologic Routine Testing – Mahantango Creek
• Similar outlet discharge
hydrographs
• Better spatial distribution of
runoff with TopoSWAT
• Improved identification of
nutrient sources with TopoSWAT
Standard SWAT
WE38 outlet
TopoSWAT
Collick et al., 2014
7. P Routine Testing: Mahantango Creek
Collick et al., in review
6000 gal ac-1
9000 gal ac-1
NewOld NewOld
6
3
0
Total P
in runoff
kg ha-1
APPLICATION
RATE
Right Timing: 1, 5, and 10 days prior to storm
1/15 1/31 2/14
New
Old
Total P
in runoff
kg ha-1
0.1
0
0.2
6000 gal ac-1
APPLICATION
TIMING
11. Figure : The delineations of the four
ditches on the 1m LiDAR (A), 3m NED
DEM (B) and 10m NED DEM (C).
Only three drainage areas are
apparent from the 10m DEM.
A. 1m DEM B. 3m DEM
C. 10m DEM
HUC12 Manokin River –
Taylor Branch
10m DEM
3m DEM
UMES
Experimental Farm
D. Manokin Watershed
Ditch 5 Ditch 7
Ditch 6
Ditch 8
Ditch 5 Ditch 7
Ditch 6
Ditch 8
Ditch 5
Ditch 6 &
Ditch 7
Ditch 8
4
12. Testing the coastal plain P Index
Drainage intensity and distance to drains
Majority of P loss occurs
in subsurface flow Empirical work
Geophysical techniques to map
shallow flow paths
14. Factory Brook – Limited watershed
monitoring
• TopoSWAT without calibration
• Automation of farm nutrient
management plan data
– 100 field management schedules
converted to modeling format in
10 minutes
• Upcoming: APLE model
comparison
15. NY P index and TopoSWAT – 1st Run
R² = 0.29
R² = 0.57
0
5
10
15
20
25
30
35
40
45
0.0 100.0 200.0 300.0 400.0 500.0 600.0
SolublePfromTopoSWAT,kgha-1
Dissolved P index
Corn and alfalfa fields
Grass fields
Very preliminary results from uncalibrated TopoSWAT run of Factory Brook
R² = 0.4785
0
0.5
1
1.5
2
2.5
3
3.5
0 50 100
SolublePoutputfrom
SWAT,kgha-1
Phosphorus applied, kg ha-1
Soluble P load in SWAT compared to dissolved P index
R² = 0.9061
0
100
200
300
400
500
600
0.0 200.0 400.0 600.0
NYDissolvedPindex
Total Source Contribution from NY P Index
Exploration
Using SWAT to assess
factors in P Index.
1st Run indicates further vetting of
results and rerunning when necessary
16. Spatial Comparison of P index and TopoSWAT
NY Dissolved
Pindex, 2009
NY Particulate
Pindex, 2009
McMahon_Farm_PartP
PARTPI_09
0.0 - 50.0
50.1 - 74.0
74.1 - 99.0
> 100
Low
Medium
High
Very High
Soluble P in
TopoSWAT, 2009
Particulate P in
TopoSWAT, 2009
17. Scenario development
Testing the P Index and SWAT
• Assess range of conditions in physiographic provinces
• Simulate management scenarios on range of representative sites
SWAT FrameworkPennsylvania P index
18. How representative are our watersheds?
Are there important site conditions we’re missing?
19. Developing reasonable scenarios
Distance to stream – what important
conditions are missing in our watersheds?
Field
management
Soils
Field
delineation
Landuse
Topography
Watershed
Soil texture
at variable
distance
from stream
21. Physiographic region – Expert panels
Feedback (problems, needs, project review)
Image PACD, http://pacd.org/2014/11/manure-management-workshop-held-in-columbia-county/
Initial meetings held for all regional expert panels
• Introduced regional project staff
• Reviewed project objectives
• Discussed survey results
Next steps…
• Follow-up meetings to review SWAT and P Index results
• Management scenario feedback
22. Allegheny Plateau
New York and Pennsylvania
Ridge and Valley/Piedmont
Pennsylvania and West Virginia Coastal Plain
Delaware
Assess opinions regarding…
– Current P Index factors (importance and reliability)
– P Index modifications (boundaries and screening tool)
Evaluation and Revision of Phosphorus Indices
Questionnaire for Nutrient
Management Experts
25. Next generation: Forecasting models
SWAT with weather forecasterWatershed stakeholder decision
support system architecture
• Forecast runoff risks (6-hrs to 3
days) across Chesapeake Bay
watershed
• Provide information for land
management decision-making to reduce
nonpoint source pollution risks
• Enabled for smart phones and other GPS-
enabled devices