1. DRAINMOD APPLICATION ABE 527 Computer Models in Environmental and Natural Resources

2. Review drainage design… soil water characteristic… hourly rainfall, daily max & min temperature relative yield input data set Note: A DRAINMOD hydrology simulation can be run without specifying a relative yield input data set.

4. Objectives After this lecture, you should get familiar with DRAINMOD application as for: How to input your own data to DRAINMOD required format; What to consider for calibration purpose; and How to use the model to predict subsurface drain flow, water table depth, and crop yield. for different drain spacings.

5. Soil:Clermont silt loam soil Slope:<1%; and land- leveled after drain installation Area:6.2 ha Southeast Purdue Agriculture Center Drainage Field (SEPAC) Monitoring : Subsurface drain flow Water quality samples

6. - Hourly rainfall - Daily maximum and minimum temperatures (measured on site or from nearby stations) Model Inputs

7. - Hourly rainfall - Daily maximum and minimum temperatures Model Inputs

9. - Drainage design parameters Model Inputs Drain spacing, L5 m10 m20 m40 m Drain depth, b75 cm Effective radius, r e 1.1 cm Distance from surface to restricting layer, h 120 cm Maximum surface storage, S m 1.0 cm Note: parameter to be calibrated— Surface micro storage S 1

10. - Soil properties: soil water characteristic, saturated hydraulic conductivity Model Inputs cont. Note: parameters to be calibrated— lateral Ksat; volumetric moisture at 0 cm tension; and the vertical hydraulic conductivity of the restrictive layer

13. - Crop parameters Model Inputs cont. MonthDayRoot depth (cm) 113.0 4253.0 5149.0 52718.0 6119.5 62024.0 72430.0 82030.0 92 92418.0 9253.0 12313.0 Time distributions of effective rooting depths

14. Calibration Procedure 1. Choose most uncertain parameters to be calibrated Range of parameter needed to be calibrated Volumetric soil moisture at 0 m tension (cm 3 /cm 3 ) LayerRange Layer 1 (0-25 cm)0.389-0.46 Layer 2 (25-30 cm)0.382-0.46 Layer 3 (30-120 cm)0.405-0.46 Horizontal Ksat (cm/hr) Layer 1 (0-25 cm)0.03-2 Layer 2 (25-30 cm)0.03-0.65 Layer 3 (30-120 cm)0.05-0.67 Vertical Ksat of restrictive layer (cm/hr)0.0005-0.003 Surface Micro storage S 1 (cm)0.3-1

15. Calibration Procedure cont. 2. Choose plot and year to be calibrated Year Drain flow ratio W20/E20W10/E10W5/E5 19851.32.51.1 198622.31.7 1987221.5 19881.821.1 19891.72.31.4 19902.12.31.2 19912.22.41.4 19923.12.41.9 19931.52.31.3 19941.61.91.6 19951.5 1.2 19961.51.91.3 19971.82.11.3 19981.521.4 19991.71.61.1 --West block and east block need to be calibrated separately. --W20 and E20 in 1988-1989 were chosen.

16. Range of parameter needed to be calibrated Volumetric soil moisture at 0 m tension (cm 3 /cm 3 ) LayerRange Layer 1 (0-25 cm)0.389-0.46 Layer 2 (25-30 cm)0.382-0.46 Layer 3 (30-120 cm)0.405-0.46 Horizontal Ksat (cm/hr) Layer 1 (0-25 cm)0.03-2 Layer 2 (25-30 cm)0.03-0.65 Layer 3 (30-120 cm)0.05-0.67 Vertical Ksat of restrictive layer (cm/hr)0.0005-0.003 Surface Micro storage (cm)0.3-1

17. Calibration Objective Functions (1) Nash-Sutcliffe efficiency: (2) Absolute percent error: Aggregated function, combining (1) and (2):

18. Automatic Calibration Parameter values against model Nash-Sutcliffe efficiencies

20. Identify Optimum Parameter Set

21. Representative observed and predicted drain flow graph

22. Observed and predicted water table graph

23. Predicted and observed relative yields

24. SUMMARY  Nash-Sutcliffe efficiency (EF) for daily drain flow ranging from -0.66 to 0.81;  EF for water table depth from -0.66 to 0.9;  Statistical tests of EF indicating insignificant difference among the three drain spacings;  Both observed and predicted relative yields indicating yields decreasing with the increase of drain spacing;  Average percent errors ranging from 1.3 to 9.7% for corn yield and from -0.8 to 10.3% for soybean yield.