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

– 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

Commercial Sugarcane- growing areas of Sri Lanka

Extents under two water regimes (ha)

Irrigated – Sevanagala (1832ha)

Hingurana(5163ha)

Kantale

Rain-fed – Pelwatte (6490ha)

Sevanagala (2387ha)

Study area

• Soil

Reddish brown earths • Terrain Undulating

• Soil bulk density1.2 – 1.65 g/cm

• Location Sevanagala Sugarcane Project

• Latitude (within)

60.26’36” - 60.20’44” • Longitude (within)

800.51’21” - 800.57’45” Rain-fed sector

Irrigated sector

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)

Rainfall Pattern

Sevanagala

050

100150200250300350400450

Month

Rai

n f

all

(mm

)Actual rainfall(mm)

Dependable (0.75)rainfall

2010 Rain Fall - Sevanagala

• 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)– January to February (minor)

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

Cane Yields in irrigated and rain-fed sectors

• Average yield in Irrigated sector is 21% higher than rain- fed sector

• This low yield in rain-fed sector can be reduced by irrigation

0

10

20

30

40

50

60

70

80

90

2004 2005 2006 2007 2008 2009

Year

Ca

ne

ha

rve

st

(t/h

a) Irrigated

Rain fed

• 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

An agro well at Sevanagala

Farmer showing water logged place in D2 area, Sevanagala

Run off in wet season at Sevanagala

Available water sources in Sevanagala

Different water harvesting techniques

Water harvesting ditches

Cement tanks

Small tanks /ponds/ Pathaha – Sri Lanka

Groundwater recharging wells

Poly lined ponds -India

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

Methodology

Land surveying in a farmer field

• Study period: from 2009 to 2010

• Three farmer fields in rain-fed area

Runoff water at lower catena of a farmer field

Placement of run off water harvester

Water logging caused to poor cane growth

• 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)

• Man power and heavy machinery were used to construct water collector

Water harvesting structures were constructed in the farmer fields (Procedure proposed by

HDRA (International Development Program, HDRA, UK)

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

Results & Discussion

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

2 4 6 8 1 0 1 2 1 4 1 6 1 8 2 0 2 2 2 4

2

4

6

8

1 0

1 2

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

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)

Re-filling behavior

Gound Water availability

Agro well at Sevanagala (August, 2009)

Rain Fall (mm)

0

100

200

300

400

500

600

1 2 3 4 5 6 7 8

Rain Fall (mm)

0

100

200

300

400

500

600

Aug-

09

Sep-

09

Oct-0

9

Nov-

09

Dec-0

9

Jan-

10

Feb-

10Dept

h to

the w

ater t

able

from

earth

surfa

ce (c

m)

SOW-3

SOW-2

SOW-1

Groundwater level fluctuations in study area (3 agro wells)

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

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.

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.

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.

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