The document discusses water quality improvement in the Upper Snake Rock Watershed in Idaho from converting irrigation systems from surface to sprinkler irrigation. It summarizes that sediment and phosphorus loss from a farm decreased by 90% when the entire farm was converted from furrow to sprinkler irrigation. Overall, sediment loss across the watershed has dramatically decreased since the 1970s due to multiple conservation practices, though the specific amount of sprinkler irrigation within sub-watersheds did not correlate directly to sediment loss. Conversion to sprinkler irrigation appears to be an effective way to reduce sediment and phosphorus runoff.

1. Water quality improvement
by converting from
surface to sprinkler irrigation.
Dave Bjorneberg, Jim Ippolito, Anita Koehn
ARS Kimberly, ID

2. Upper Snake Rock Watershed
August 2009

3. Upper Snake Rock Watershed – Idaho
1. 82,000 ha with 70,000 ha cropland (85%).
2. 270 mm annual precipitation, 90 mm May to Sept.
3. Daily rainfall >20 mm only six times during 2005-2008,
five times in 2005.
4. About 40% sprinkler irrigated.
5. Monitoring for the Conservation Effects Assessment
Project (CEAP) began in 2005.

4. 0
200
400
600
800
1000
1200
1400
2005 2006 2007 2008 Average
Irrigation Rock Creek Precipitation
USR Water Input (mm)

5. 1982
2006

6. • 24 return flow monitoring sites.
• 5 sub-watersheds, 150 to 600 ha, 5 to 50% sprinkler irrigation

7. -1500
-1000
-500
0
500
1000
1971 2005 2006 2007 2008
SuspendedSediment(kg/ha)
Inflow
Outflow
Net
Sediment loss has decreased since 1971 when watershed was 95% furrow irrigated.
USR Watershed

9. R
2
= 0.08
0
2000
4000
6000
8000
10000
0% 10% 20% 30% 40% 50% 60% 70% 80%
Sprinkler Irrigated Area (%)
SedimentLoad(lb/a)

10. R
2
= 0.88
R
2
= 0.64
R
2
= 0.07
R
2
= 0.07
0
2000
4000
6000
8000
10000
0% 10% 20% 30% 40% 50% 60%
Furrow Irrigated Row Crop (%)
SedimentLoad(lb/a)
PC1 (10%)
PC2 (50%)
TF1 (30%)
TF3 (65%)
EC (15%)

11. R
2
= 0.49
R
2
= 0.32
R
2
= 0.64
R
2
= 0.52
0.0
0.2
0.4
0.6
0.8
1.0
1.2
0% 10% 20% 30% 40% 50% 60%
Furrow Irrigated Row Crop (%)
DissolvedPhosphorusLoad(lb/a)
PC1 (10%)
PC2 (50%)
TF1 (30%)
TF3 (65%)
EC (15%)

12. outlet
Sprinkler
F out
F in
Furrow
Added two sites in 2012 within the PC1 sub-watershed (250 ha)

13. 0
100
200
300
400
500
600
700
800
900
1000
2005 2006 2007 2008 2010 2012 2013
SuspendedSediment(kg/ha)
PC1 sub-watershed (July)
25%
decrease
85%
decrease

14. 0.00
0.20
0.40
0.60
0.80
1.00
2005 2006 2007 2008 2010 2012 2013
TotalPhosphorus(kg/ha)
PC1 sub-watershed (July)

15. 0.00
0.02
0.04
0.06
0.08
0.10
2005 2006 2007 2008 2010 2012 2013
DissolvedPhosphorus(kg/ha)
PC1 sub-watershed (July)

16. 0
50000
100000
150000
200000
250000
July Aug. July Aug.
F in
F out
PC1
Suspended Sediment Loads in PC1 (kg)
2012 2013
90% reduction in F out from 2012 to 2013.

17. 0
100
200
300
400
July Aug. July Aug.
F in
F out
PC1
Total Phosphorus Loads in PC1 (kg)
2012 2013

18. 0
2000
4000
6000
8000
2012 2013 2014
F in
F out
PC1
June-July Average Sediment
Concentrations (mg/L)

19. outlet
Sprinkler
F out
F in
Furrow

20. Summary
• Sediment loss from the USR has dramatically decreased
since 1970 due to multiple practices.
• No correlation between amount of sprinkler irrigation and
sediment loss among sub-watersheds.
• Sediment and P loss from a farm decreased 90% when
the entire farm was converted to sprinkler irrigation.
• Furrow irrigation management or conversion to sprinkler
irrigation is the key to reducing sediment and
phosphorus losses.

21. Questions?