1. Modeling of Critical Areas for DRP Runoff and Targeting Strategies
Rem Confesor Jr.
Research Scientist
NCWQR, Heidelberg University
Team Meeting #5
Great Lakes Protection Fund Grant
A Phosphorus Soil Test Metric
To Reduce Dissolved Phosphorus Loading to Lake Erie
July 24, 2013 1

2. Watershed Modeling CONSTRAINTS: SPACE & TIME resolution2

3. A very simple conceptual model…
Issues:
One precipitation value for the whole watershed.
Model is not a good representation of reality.
Coefficients are unknown: need for calibration.
Spatially lumped across the whole watershed,
Yearly time step
Precipitation
Runoff flow
Infiltration
Yearly Runoff flow = (x)Precipitation + y(Infiltration) + Constant 3

4. A little bit of improvement…
Precipitation (P)
Basic spatial unit
Evapo-
transpiration (ET)
Evaporation (E)
Soil
storage
(S)
Runoff
Flow (R)
Infiltration (I)
Lateral
subsurface
Flow (L)
Groundwater
recharge (G)
S = P - ET - E - I - R;
I = G + L;
Discharge (Q) = (a)R + (b)L + c 4

5. The hydrologic response unit (HRU)- basic spatial unit:
unique combination of
slope, landuse, & soil. +
Digital elevation model
(slope/terrain)
Land use/
crop cover
Soil type
Hydrologic Response Units (HRUs) 5

6. The SWAT Model: Physically-based. Daily time step.
Terrain
Weather
Soil
Land use/
crop cover
Agricultural practices & mgt.: tillage, fertilizer, etc.
Flow, sediment,
nutrients (N & P), etc.
The SWAT Model:
Physically-based.
Daily time step.
Long-term simulation of effects of changes in ag. management.
“RELATIVE” output changes due to these management changes. 6

7. SWAT SETUP: CROP ROTATION
2006, Corn
2007, Soybean
2008, Corn
2009, Soybean 7

8. Change in DRP, lb/acre P2O5
Baseline to NoTill
Baseline to NoTill + Inc 8

9. Change in DRP, lb/acre P2O5
NoTill + Bcast TO NoTill + In
NoTill + In TO Disc Plowed + In 9

10. Change in Particulate P, lb/acre P2O5
Baseline to NoTill
Baseline to NoTill + In 10

11. Change in Particulate P, lb/acre P2O5
NoTill + Bcast TO NoTill + In
NoTill + In TO Disc Plowed + In 11

12. THANK YOU! Rem Confesor rconfeso@heidelberg.edu 419-448-2204
Rem Confesor 12