This document summarizes a study on the impacts of subsurface drainage and opportunities for controlled drainage in eastern South Dakota. The study used a 63-year simulation to analyze water yield from drained and undrained soils. It found that controlled drainage could have saved water in 36 of the 63 years by preventing it from leaving the field. Controlled drainage was most beneficial in wet years, preserving soil moisture 100% of the time in the wettest 25% of years. However, more research is still needed on how controlled drainage affects crop yields and downstream nutrient loads.

1. IMPACTS OF
SUBSURFACE
DRAINAGE ON
WATER YIELD AND
OPPORTUNITIES
FOR CONTROLLED
DRAINAGE IN
EASTERN SOUTH
DAKOTA
John McMaine
Ag and Biosystems
Engineering

2. ACKNOWLEDGEMENTS
▪Those who have gone before
▪ Govinda Karki
▪ Morghan Hurst
▪ Todd Trooien
▪ Chris Hay
▪ Jeppe Kjaersgaard
▪ Kristen Almen
2

3. ACKNOWLEDGEMENTS
▪Thank you to those who supported this project,
especially:
▪ South Dakota Agricultural Experimental Station
▪ South Dakota NRCS
▪ South Dakota Corn Utilization Council
3

5. 2019 South Dakota Crop Insurance Claims
Data Source – USDA RMA
0% 10% 20% 30% 40% 50% 60% 70%
Decline in Price
Hail
Other
Cold Wet Weather
Excess Moisture

6. Changes in precipitation amount
• Average annual precipitation
has increased from 2 to over 5
inches (Hay & Todey, 2011)
• Since 1990, South Dakota has
averaged 14% more 1-inch
rain events (NOAA)
• Winter precipitation is
projected to increase by 10%–
20% (NOAA) Hay & Todey, 2011: Change in mean annual
precipitation, in inches, for the period of 1991-2009 as
compared to 1961-1990

7. Changes in precipitation timing
Hay & Todey, 2011: Change in winter (December,
January, and February) precipitation, as a percentage,
for the period of 1991-2009 as compared to 1961-1990
Hay & Todey, 2011: Change in fall (September,
October, and November) precipitation, as a percentage,
for the period of 1991-2009 as compared to 1961-1990

8. METHODS & MATERIALS
• 63 year period
• Site in Clay County, SD
DRAINMOD
• Average Annual Runoff, Drainage, ET
Water Yield
• If drainage was present
• If water level was not higher than board height
Opportunities for Controlled
Drainage?
8

9. 9 Graphic courtesy of Dr. Chris Hay, Iowa Soybean Association (formerly SDSU Extension Water Management Engineer)
© 2022 South Dakota Board of Regents

10. Water yield in drained vs. undrained
0
2
4
6
8
10
Undrained
DI
0.125
DI
0.250
DI
0.375
Undrained
DI
0.125
DI
0.250
DI
0.375
Undrained
DI
0.125
DI
0.250
DI
0.375
Undrained
DI
0.125
DI
0.250
DI
0.375
Ac-Albaton (Silty-
Clay)
EhA-Egan (Silty
Clay loam)
Bm-Bon (Clay
loam)
Tr-Ticonic (Sandy
loam)
Long
Term
average
water
Yield
(cm)
Runoff
Drainage
Figure from dissertation of Dr. Govinda Karki

11. Water yield with respect to spacing
0
2
4
6
8
10 UD
8.5
10.0
12.5
15.0
17.5
20.0
25.0
30.0
UD
15.0
17.5
20.0
22.9
25.0
30.0
35.0
40.0
UD
15.0
17.5
20.0
22.9
27.5
32.5
40.0
47.5
UD
20.0
22.9
25.0
30.0
35.0
40.0
45.0
50.0
55.0
60.0
Ac EhA Bm Tr
Long-Term
avereage
Water
Yield
(cm)
Spacing (m) for Four Selected Soil Type
Runoff
Drainage

12. 2018 South Dakota Crop Insurance Claims
Data Source – USDA RMA
0% 5% 10% 15% 20% 25% 30% 35% 40%
Wind
Cold Winter
Heat
Cold Wet Weather
Decline in Price
Hail
Other
Drought
Excess Moisture

13. 2017 South Dakota Crop Insurance Claims
0% 5% 10% 15% 20% 25% 30% 35% 40%
Wind/Excess Wind
Heat
Other
Decline in Price
Cold
Hail
Excess Moisture
Drought
Data Source – USDA RMA

14. RESULTS
Corn Brookings Clay Codington Minnehaha Total
Both 22 21 23 23 89
Only Excess
Moisture
8 8 6 6 28
Only Drought 0 1 1 1 3
Soybean
Both 23 26 27 24 100
Only Excess
Moisture
7 4 3 6 20
Only Drought 0 0 0 0 0

15. RESULTS
The table to the right shows
the average, minimum, and
maximum percentages of
total indemnified acres
(drought/excessive moisture)
by total planted acres for a
30-year span (1991-2020).
Average
(SB)
Minimum
(SB)
Maximum
(SB)
Average
(Corn)
Minimum
(Corn)
Maximum
(Corn)
Dry
Brookings 1.86% 0.00% 12.03% 1.76% 0.00% 14.17%
Clay 5.68% 0.00% 74.03% 6.19% 0.00% 65.98%
Codington 4.71% 0.00% 22.77% 4.48% 0.00% 33.24%
Minnehaha 2.23% 0.00% 32.40% 2.90% 0.00% 54.83%
Wet
Brookings 3.79% 0.26% 22.94% 4.99% 0.10% 37.28%
Clay 9.77% 0.14% 47.99% 10.82% 0.00% 62.09%
Codington 5.48% 0.13% 26.64% 7.20% 0.22% 20.63%
Minnehaha 3.18% 0.03% 28.26% 2.60% 0.00% 14.61%

16. RESULTS
▪ The amount of indemnified drought/excessive moisture insurance acre claims divided by the total
amount of acres planted in the county per year from 1991-2020 for soybeans.

17. RESULTS
▪ The amount of indemnified drought/excessive moisture insurance acre claims divided by the total amount
of acres planted in the county per year from 1991-2020 for corn.

18. RESULTS
▪ Ratio between 0.5 – 1.5 showed similar amount of
both moisture extremes coexisting
▪ Subsurface drainage can address excess moisture, it
cannot address drought.
▪ County-years in which both moisture extremes
coexist may be good candidates for CD.
▪ Corn - 17 of 120 county-years (14%)
▪ Soybeans – 15 of 120 county-years (12.5%)
𝑇𝑜𝑡𝑎𝑙 𝑁𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝐼𝑛𝑑𝑒𝑚𝑛𝑖𝑓𝑖𝑒𝑑 𝐷𝑟𝑜𝑢𝑔ℎ𝑡 𝐴𝑐𝑟𝑒𝑠
𝑇𝑜𝑡𝑎𝑙 𝑁𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝐼𝑛𝑑𝑒𝑚𝑛𝑖𝑓𝑖𝑒𝑑 𝑊𝑒𝑡 𝐴𝑐𝑟𝑒𝑠
= 𝑅𝑎𝑡𝑖𝑜

19. METHODS & MATERIALS
• 63 year period
• Site in Clay County, SD
DRAINMOD
• Average Annual Runoff, Drainage, ET
Water Yield
• If drainage was present
• If water level was not higher than board height
Opportunities for Controlled
Drainage?
19

20. ▪ The depth of water (cm) prevented from leaving the field due to CD on a year-to-year
basis from 1950-2012.
▪ There was potential for CD in 36 of 63 total years (58%)
RESULTS
0
2
4
6
8
10
12
14
1950
1952
1954
1956
1958
1960
1962
1964
1966
1968
1970
1972
1974
1976
1978
1980
1982
1984
1986
1988
1990
1992
1994
1996
1998
2000
2002
2004
2006
2008
2010
2012
Depth
of
Water
Prevented
from
Leaving
the
Field
(cm)
Year
The Amount of Water Controlled Drainage Could have Saved per
Year
Sum of "Water Saved 30.5" Sum of "Water Saved 45.7" Sum of "Water Saved 61.0"
Sum of "Water Saved 76.2" Sum of "Water Saved 91.4" Sum of "Water Saved 106.7"

21. RESULTS
0
2
4
6
8
10
12
14
34.14 40.42 51.89 56.21 58.52 62.07 64.21 66.71 68.5 71.83 77.74 81.16 86.08
Amount
of
Water
Saved
per
Year
(cm)
Amount of Rainfall per Year (cm)
Water Saved per Rainfall per Year
Sum of "Water Saved 30.5" Sum of "Water Saved 45.7" Sum of "Water Saved 61.0"
Sum of "Water Saved 76.2" Sum of "Water Saved 91.4" Sum of "Water Saved 106.7"
Average Years Wet Years
Average Years
Dry Years
▪ The depth of water (cm)
prevented from leaving the
field due to CD from the
least amount of annual
precipitation to the greatest
amount of annual
precipitation (cm) from
1950-2012.
▪ Wet years (top 25% annual
precipitation)
• 16 of 16 years (100%)
▪ Average years (middle 50%
annual precipitation)
• 18 of 31 years (58%)
▪ Dry years (bottom 25%
annual precipitation)
• 2 of 16 years (12.5%)

22. ▪ CD is most beneficial to crop growth when timely rainfall can be held in the soil profile
for use during a subsequent short dry period.
▪ An automated controlled drainage system that accounts for soil moisture, water table
depth, crop water demand, and short-term weather forecasting would have the
capability to dynamically adjust the soil moisture held in or released from the field
based on the current, real-time scenario.
▪ Previous research has demonstrated variable crop growth improvement using CD
▪ Previous studies have demonstrated significant NO3 load reduction using CD.
DISCUSSION

23. ▪ This study found that CD only preserves soil moisture a
little over half of the time, with only 3.1% of this time
being dry years and 28.6% of this time in average
moisture years.
▪ Even with the limited amount of years CD could
influence soil moisture, research still needs to be done
about the effect it has on crop yield and downstream NO3
concentrations.
CONCLUSION

24. https://extension.sdstate.edu/tags/streamlines-podcast
Twitter – @SDSUExtWaterMan
Email – john.mcmaine@sdstate.edu

25. IMPACTS OF
SUBSURFACE
DRAINAGE ON
WATER YIELD AND
OPPORTUNITIES
FOR CONTROLLED
DRAINAGE IN
EASTERN SOUTH
DAKOTA
John McMaine
Ag and Biosystems
Engineering