L.M.J.R Wijayawardhana, K.H.D Abeyrathna, W.R.G Witharama & A.P Keerthipala Sugarcane Research Institute of Sri Lanka, Uda Walawe International Forestry and Environment Symposium 2011 Annual Symposium organized by Department of Forestry and Environmental Science, University of Sri Jayewardenepura, Nugegoda, Sri Lanka http://fesympo.sjp.ac.lk/

1. Run-off Water Harvesters and
Agro-wells for Supplementary
Irrigation of Rain-fed
Sugarcane
(A Preliminary Investigation)
L.M.J.R Wijayawardhana, K.H.D Abeyrathna, W.R.G Witharama
&
A.P Keerthipala
Sugarcane Research Institute of Sri Lanka, Uda Walawe

2. Commercial Sugarcane-
growing areas of Sri Lanka
– Pelwatte - Sugar, Syrup and Ethanol
– Sevanagala – Sugar, Syrup and Ethanol
– Hingurana – Re opened (2009)
– Kantale – to be re opened/ no production
– Badulla – Jaggery / cottage-level
– Kilinochchi – Pilot project started in
2010 /Jaggery

3. Extents under two water
regimes (ha)
Irrigated – Sevanagala (1832ha)
Hingurana(5163ha)
Kantale
Rain-fed – Pelwatte (6490ha)
Sevanagala (2387ha)

4. Study area
• Location
Sevanagala Sugarcane Project
• Latitude (within)
60.26’36” - 60.20’44”
• Longitude (within)
Rain-fed sector
800.51’21” - 800.57’45”
• Soil
Reddish brown earths
• Terrain
Undulating Irrigated sector
• Soil bulk density
1.2 – 1.65 g/cm

5. Agro-ecological parameters – Sevanagala sugar
Project
• Situated in DL1 AEZ
• Annual rainfall
– 1324.4 mm ±282.4 (1984-2010)
• Annual pan evaporation
– 1590.8 mm ±198.7 (1984-2010)

6. Rainfall Pattern
• Annual total rain fall (2010) - 1431.4mm
• Rainy seasons - October to December (Maha)
- March to May (Yala)
• Dry spells and durations
– June to September (major)
Sevanagala
– January to February (minor) 450
400 Actual rainfall
Rain fall (mm) 350 (mm)
300 Dependable (0.75)
250 rainfall
200
150
100
50
0
ec er
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A y
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Fe ary
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N obe
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Ju
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Ju
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em
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A
br
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Ja
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Month
2010 Rain Fall - Sevanagala

7. Irrigation in Sevanagala
• Furrow irrigation – all the commercial cane-growing
areas
• Sprinkler irrigation – only in seed cane nurseries
• Irrigation interval – 9 – 12 days
• Crop water requirement – 1500mm/year
• Rainfall supplies approximately 2/5 of this requirement
• 12 days

8. Cane Yields in irrigated and rain-
fed sectors
90
80
Irrigated
Cane harvest (t/ha)
70
Rain fed
60
50
40
30
20
10
0
2004 2005 2006 2007 2008 2009
Year
• Average yield in Irrigated sector is 21% higher than rain-
fed sector
• This low yield in rain-fed sector can be reduced by
irrigation

9. • The supplementary irrigation in the rain-
fed area is critically limited by scarcity of
water
– Potential water sources
• Groundwater in confined aquifers
• Groundwater in unconfined aquifers
• Run off water harvesting

10. Available water sources
in Sevanagala
An agro well at Sevanagala
Run off in wet season at Sevanagala
Farmer showing water logged place in
D2 area, Sevanagala

11. Different water harvesting
techniques
Cement tanks
Poly lined ponds -India
Water harvesting ditches
Small tanks /ponds/ Pathaha – Groundwater
Sri Lanka recharging wells

12. Objective of the study
• To investigate the possibility of run-off
water harvesting and using agro-wells for
supplementary irrigation in rain-fed
sugarcane fields in Sevanagala sugar
project

13. Methodology
• Study period: from 2009 to 2010
• Three farmer fields in rain-fed area
Land surveying in a farmer field
Runoff water at lower catena of a farmer field

14. Placement of run off water
harvester
• constructed the run off water harvesting
structures at the low-lying areas of the
farmer field which is often flooded during
the rainy season (this area can’t be
utilized for sugarcane cultivation due to ill
draining)
Water logging caused to poor cane growth

15. Water harvesting structures were
constructed in the farmer fields (Procedure proposed by
HDRA (International Development Program, HDRA, UK)
• Man power and heavy machinery were used to
construct water collector

16. Data Collected
• Volume of the water harvester
– Practical approach (actual water volume) –by pumping/ water
flow meter
– Mathematical approach
• No. of days required to re-fill the water
harvester after each irrigation
• Flow rates of the drain
• Monthly rainfall data – From SSIL
Pump installation at farmer field

17. Results & Discussion

18. Maximum possible capacity of
water harvester
• The water harvesting structure can store
125 -150 m3 of water
• Further increase of run off water
harvester’s capacity is limited because it,
• reduces productive cultivable area
• shallow groundwater level limits the depth
• causes severe drainage problem during wet
season / easiness to repair & de-silting, etc.
• high cost of machinery
• Farmer’s attitudes

19. 1 2
1 0
8
6
4
2
2 4 6 8 1 0 1 2 1 4 1 6 1 8 2 0 2 2 2 4
Capacity - 125 to 150 m3
The capacity of constructed water
harvester is enough to irrigate only 0.2 ha
sugarcane field under the conventional
furrow irrigation method

20. Re-filling behavior
Rainfall occurs (21mm/hr or more)
during dry spell creates surface run off
in RBE soils (Shanmuganathan, 1992)
and recharge the water collector up to
full capacity
In-flow rate (after 9 days to heavy rain
in April, 2009) is 180 l/min
During heavy drought, it was 8.2 – 11.4
L/min (July, 2009)

21. Gound Water availability
Rain Fall (mm)
600
600
Depth to the water table from earth surface (cm)
SOW-3
500 500
SOW-2
400 SOW-1 400
300 300
200 Rain Fall (mm) 200
100 100
0 0
1 2 3 4 5 6 7 8
Jan-10
Oct-09
Sep-09
Dec-09
Feb-10
Nov-09
Aug-09
Agro well at Sevanagala
Groundwater level fluctuations in study area (3 agro wells) (August, 2009)
Agro-wells were heavily utilised for irrigation during the 2nd
dry spell in 2009
Field observations revealed that, these wells were refilled
approximately within a week after each irrigation

22. Conclusions
• 150m3 of run-off water can easily be stored in the
proposed water collectors in Sevanagala rain-fed
sugarcane fields
• Water stored in these run-off water harvesters in
Sevanagala rain-fed farmer fields is not sufficient to
practice conventional furrow irrigation.
• Supplementary irrigation systems can be introduced to
rain-fed sugarcane fields in Sevanagala sugar project, by
incorporating both runoff water harvesters with agro-wells.

23. Suggestions
• Run-off water harvesting in Sevanagala
rain-fed sugarcane fields is not sufficient
to practice conventional furrow irrigation.
Hence, it would be best under Regulated
Deficit Irrigation
• Over-head irrigation which makes
possible controlling irrigation depth,
would be more practical method to
practise regulated deficit irrigation.

24. Further study
• Easy handling and low-cost overhead
irrigation system is being constructed with
locally available materials, and is powered
by two-wheel tractors that are more
common in the sugarcane farming
community at Sevanagala.

25. Acknowledgements
• Dr H.K Sunil – Former Director, Sugarcane Research Institute
• Mr. D.D Nanayakkara - Former Plantation Manager, Sevanagala
Sugar Industries Limited
• Mr. N.A.H.K Athula Siridewa – Agriculture Superintendent
(Plantation), Sevanagala Sugar Industries Limited
• Mr. M.U.K.U Kumara - Agriculture Superintendent (Division 3),
Sevanagala Sugar Industries Limited
• Mr. Nevilson - Former Agriculture Superintendent (Division 2),
Sevanagala Sugar Industries Limited