This document summarizes a study on drainage water recycling systems and their ability to reduce nutrient losses based on the size of on-farm water storage. The study uses data from 2006-2016 from the Davis Purdue Agriculture Center in Indiana to model various storage sizes from 2-10% of field area. Larger storage sizes were able to capture more annual drain flow and reduce nitrogen and phosphorus loads, with 8% storage capturing 66% of drain flow on average. The document concludes that drainage water recycling systems with storage sizes of 4-8% of field area can significantly reduce nutrient losses.

1. MANAGING WATER FOR TOMORROW’S AGRICULTURE
Nutrient loss reduction potential of
drainage water recycling systems based on
on-farm water storage size
Ben Reinhart, Project Manager
Jane Frankenberger, Project Director
Agricultural and Biological Engineering, Purdue University

2. MANAGING WATER FOR TOMORROW’S AGRICULTURE
Water storage
and management
in the Midwest
• Improve
drainage to
support
production
• Tile drains
increase loss of
nitrate (and
phosphorus) Outlet
(i.e. stream)

3. MANAGING WATER FOR TOMORROW’S AGRICULTURE
Options for
reducing
nutrient loads
• Reduction
efficiencies are
highly variable
across practices
Source: Iowa Nutrient Reduction Strategy Science Assessment
Nitrogen Reduction Target = 41%

4. MANAGING WATER FOR TOMORROW’S AGRICULTURE
Drainage water recycling

5. MANAGING WATER FOR TOMORROW’S AGRICULTURE
• How will this
vary across
climate and
soils?
• How much
storage is
needed to meet
crop or water
quality targets?
Designing drainage water recycling systems

6. MANAGING WATER FOR TOMORROW’S AGRICULTURE
Water balance
in DWR systems
• Track:
1. Daily drain flow
3. Water level
and volume
2. Soil water
storage

7. MANAGING WATER FOR TOMORROW’S AGRICULTURE
Soil water
storage
• Defining the soil
water reservoir
• Variables:
+ Eff. Precip. (Pe)
+ Irrigation (I)
- Evaporation/
Transpiration
(ET)
Daily Soil Water = Pe + I – ET

8. MANAGING WATER FOR TOMORROW’S AGRICULTURE
Soil water
storage
• Effective
Precipitation
• FAO CLIMWAT
• Reference/Crop
ET
• Daily climate on-
site (L. Bowling,
Purdue)
• FAO CropWat Kc
(Maize)

9. MANAGING WATER FOR TOMORROW’S AGRICULTURE
Storage level
and volume Avg. Depth
Area
• Variables:
+ Drain flow (D)
+ Precipitation (P)
- Evap.(E)
- Irrigation (I)
- Seepage (S)
Daily Water Volume =
D + P – E – I – S

10. MANAGING WATER FOR TOMORROW’S AGRICULTURE
Water level and
volume
• Measured daily
drain flow and
precipitation
• Evaporation (NWS
pan avg. monthly values)
• Seepage (3mm/day
constant)
0
2
4
6
8
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
mm/day
Evaporation
0
2
4
6
8
10
12
14
mm/day Drain flow

11. MANAGING WATER FOR TOMORROW’S AGRICULTURE
Water balance
in DWR systems
• As water is
added to the
system:
1. Capture if
capacity > flow
2. Bypass if
capacity < flow

12. MANAGING WATER FOR TOMORROW’S AGRICULTURE
Water balance
in DWR systems
• As water is
removed from
the system:
1. Irrigation
applied if
demand < stored
volume
2. Storage Deficit
if demand >
stored volume

13. MANAGING WATER FOR TOMORROW’S AGRICULTURE
Davis Purdue
Agriculture
Center (DPAC)
Field Data
(2006-2016, daily)
• Drain flow
• Weather
• Water Quality
• Nitrate-N
• Total Phosphorus
(2012-2016)
Data from Saadat, Bowling,
Frankenberger

14. MANAGING WATER FOR TOMORROW’S AGRICULTURE
Davis Purdue Agriculture Center (DPAC)
Drain flow: 368 mm/yr (avg.); 232 mm Min., 470 mm Max
0
2
4
6
8
10
12
14
16
Nitrate-Nitrogen(mg/l)
0
0.05
0.1
0.15
0.2
0.25
0.3
TotalPhosphorus(mg/l)

15. MANAGING WATER FOR TOMORROW’S AGRICULTURE
Various Sizes of
Storage
2% of field area
4% of field area
6% of field area
8% of field area
10% of field area
Avg. Depth: 3 m
Field Area: 80 ac.
10%
8%
6%
4%
2%
Drainage water recycling in MI
5 acres 1 acre
each

16. MANAGING WATER FOR TOMORROW’S AGRICULTURE
Results: % of Annual Drain Flow Captured
0%
20%
40%
60%
80%
100%
2% 4% 6% 8% 10%
Storage Area/Field Area
Avg

17. MANAGING WATER FOR TOMORROW’S AGRICULTURE
0
10
20
30
40
Orig.
Load
2% 4% 6% 8% 10%
Storage Area/Field Area
Avg
Results: Nitrate-N Load Captured (kg/ha)
N

18. MANAGING WATER FOR TOMORROW’S AGRICULTURE
0
0.2
0.4
0.6
0.8
1
Orig.
Load
2% 4% 6% 8% 10%
Storage Area/Field Area
Avg
Results: Total Phosphorus Load Captured (kg/ha)
N
P

19. MANAGING WATER FOR TOMORROW’S AGRICULTURE
0
30
60
90
120
150
180
210
Desired 2% 4% 6% 8% 10%
Storage Area/Field Area
Avg
Results: Applied Irrigation (mm/yr)

20. MANAGING WATER FOR TOMORROW’S AGRICULTURE
Results: Spatial Variability
DPAC (Indiana)
Drain Flow: 232-470 mm
Southeast Research Farm (Iowa)
Drain Flow: 56-535 mm
0%
20%
40%
60%
80%
100%
2% 4% 6% 8% 10%
Storage Area/Field Area
Avg
0%
20%
40%
60%
80%
100%
2% 4% 6% 8% 10%
Storage Area/Field Area
Avg
Data courtesy Dr. Matt Helmers, Iowa State University
Example - % of Annual Drain Flow Captured

21. MANAGING WATER FOR TOMORROW’S AGRICULTURE
Conclusions
How much
storage do we
need?
• 4% storage= 31%
avg. reduction
• 6% storage= 49%
avg. reduction
• 8% storage= 66%
avg. reduction
DWR
4%
DWR
6% DWR
8%

22. MANAGING WATER FOR TOMORROW’S AGRICULTURE
Next Steps
1. Evaluation
across variable
climate and
soils
2. Development
of online tool
for evaluating
DWR systems

23. THIS MATERIAL IS BASED UPON WORK THAT IS SUPPORTED BY THE NATIONAL INSTITUTE OF FOOD AND AGRICULTURE, U.S. DEPARTMENT OF AGRICULTURE,
UNDER AWARD NUMBER 2015-68007-23193, “MANAGING WATER FOR INCREASED RESILIENCY OF DRAINED AGRICULTURAL LANDSCAPES”,
HTTP://TRANSFORMINGDRAINAGE.ORG. ANY OPINIONS, FINDINGS, CONCLUSIONS, OR RECOMMENDATIONS EXPRESSED IN THIS PUBLICATION ARE THOSE OF
THE AUTHOR(S) AND DO NOT NECESSARILY REFLECT THE VIEW OF THE U.S. DEPARTMENT OF AGRICULTURE.
University of Missouri
MANAGING WATER FOR TOMORROW’S AGRICULTURE
Managing Water for Increased
Resiliency of Drained Agricultural
Landscapes