The document summarizes a study on using low-cost rainwater harvesting tanks to improve incomes for households in Sri Lanka's dry zone. Nine farmers built 5m3 ferrocement tanks to collect surface runoff. They tested three cropping patterns: single crops between contours, mixed crops on contours, and N-fixing trees on contours. Results showed no difference in water collected or income increase between patterns. However, incomes doubled in Maha season compared to before. Most importantly, water availability allowed cultivation in the Yala season for the first time. Farmers' incomes increased and they used excess water for other purposes like brick making.

1. RAINWATER HARVESTING FOR HOME GARDENS IN DRY ZONE OF
SRI LANKA
P. A. Weerasinghe
Faculty of Agriculture, Rajarata University of Sri Lanka
Puliyankulama, Anuradhapura, Sri Lanka.
aruni50@yahoo.com
T. N. Ariyananda
Lanka Rain Water Harvesting Forum
28/3A, Subhadrarama Mawatha
Nugegoda, Sri Lanka
tanuja@sltnet.lk
C.S. Weeraratna
Sugarcane Research Institute
Telawala Road
Ratmalana, Sri Lanka
csweera@sltnet.lk
ABSTRACT
A study was conducted on how harvested rainwater in low cost surface runoff tanks would
improve the income level of households living in the dry zone area of Sri Lanka. To collect rain
water, low cost ferro cement surface runoff tanks with 5 m3 capacity were built at the bottom
of the land towards the slope, where the runoff rainwater flows through the contours into the
tank. Three cropping patterns were introduced, ie. one crop planted between contour bounds,
mixed crops planted on the same contour and N- Fixing trees (i.e. Gliricidia) planted on the
contour. The contouring the land helped to direct water to the tank as well as to control
erosion. Results showed that the three different cropping patterns used had no significant
difference in amount of water collected in tank or to the income increase by cultivation.
However, regardless of the cropping patterns 100% of income increase was observed in Maha
in compare with the income prior to the project intervention. Due to availability of water,
farmers started cultivate in Yala 2004 which they have not done in past. Farmers used excess
tank water not only for cultivation but also to generate income by other means eg. brick
making.
INTRODUCTION
Out of 6 million hectares of Sri Lanka, around 4 million are in the Dry Zone which has five
Agro- Ecological Regions (AERs). The rainfall in the Dry Zone varies from 750 mm to 1500
mm. Around 1000 mm is received during the Maha season (October – February) and 500 mm
in the Yala season (April – July).
Paddy is mainly cultivated in the Dry Zone. Among field crops such as chilly, maize, pulses,
some vegetables and fruits crops are taking prominent place in dry zone cultivation.. An
average lowland holding is 0.4 hectares and an upland holding is 1.2 hectares. The
agricultural productivity in the Dry Zone has stagnated during the last few decades mainly due
to a host of factors and one is inadequate water.
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2. Agriculture is the main source of income of nearly 80% of the people living in these areas.
Poverty is widespread mainly in the Dry Zone of Sri Lanka. For example in Anuradhpura
district in dry zone, around 50% of the households are below poverty level (Annual Report,
Samurdhi Authority 2002) ie. below a monthly income of Rs.1500/- which is equivalent to US$
15 Hence successful crop production determines to a great extent their poverty level and
depends on the efficient use of available water and some other factors. The rainfall is less
during Yala season and available water for cultivation of crops during this period is
inadequate.
From the total rainfall around 25% of rain water is lost in the form of surface run-off and
conserving this water will not only promote crop growth in areas where water is limiting, but
will also reduce soil erosion. Among various methods of storing of water harvesting and
conservation, the most common and economical method is storing of water in sub-surface
tanks (Gould J and Nissen P. E, 1999). Therefore, a study was conducted on how harvested
rainwater in low cost surface runoff tanks would improve the income level of households living
in the dry zone area of Sri Lanka.
METHODOLOGY OF THE STUDY
The Site Selection
The selected site, Kurundamkulama, Unit 11 is located within the Mihintale Divisional
Secretariat in Anuradhapura district in Sri Lanka. The area gets an annual average rainfall of
1000 mm in two seasons, from October to December, during the Maha season (around 700
mm) and from May to July, during the Yala season (around 300 mm). The main source of
water for the village is one tube well and one agro well.
Selection of Beneficiaries
From the socio economic survey conducted within households in the village, nine (9)
households were selected for the research after circulating a questionnaires and following a
brief discussion to confirm the facts stated in questionnaires (Table1).
Questionnaires were mainly focused on,
Ø Details of Family members
Ø Educational level
Ø Income Sources
Ø Description of land
Ø Last year income gained in Maha and Yala seasons
The selection criteria for Farmers were based on scarcity of water for cultivation, monthly
income level (below Rs.1,500/- which is US $ 15. cultivable land minimum of one acre (with
one exception), sloping land and willingness to participate.
Information Generated From the Questionnaire
The information generated from the questionnaire is summarised in the table 1.The main
occupation of the household is farming. The education level is generally up to G.C.E. Ordinary
Level. The average income earned during 2002 Maha crop production was Rs. 775/- per
farmer. Only one farmer earned an income of Rs. 1,250/- during 2002 Yala and rest of the
households did not cultivate during Yala season due to non availability of water. Ninety
percent of the households surveyed are below the poverty line (monthly income is below Rs.1,
500/-). The average number in household is four (4) members.
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3. Table 01: The summarised results of the survey conducted in the Kurundamkulama, unit 11
village.
Monthly No. of Acers
No. of Condi 2002 2002
Income No. of Cultivated
memb tion of Product Income (Rs)
Farmer (Rs) Acers 2002
ers Land Maha Yala Maha Yala Maha Yala
Farmer 1 3 1000/- 1 Slope ½ ¼ Chilli 1350/-
Long
bean
Farmer 2 Chilli
Brinjal
2 1000/- 3 1/2 Slope 1 1675/-
Long
bean
NOT CULTIVATED
NOT CULTIVATED
Farmer 3 4 1000/- 1 Slope ¾
NOT CULTIVATED
Farmer 4 Chilli
5 1500/- 1½ Slope 1 1000/
Brinjal
Farmer 5 1000/- Chilli
4 1 Slope ¾ 750/-
Maize
Farmer 6 4 1500/- 1 Slope ¾ Chilli 600/-
Farmer 7 4 1000/- 1 Slope ½ Maize
Farmer 8 4 1000/- ½ Slope ½ Chilli 1000/
Farmer 9 Chilli
Long
6 2000/- 1½ Slope 1 ½ 600/- 1250/
bean
Brinjal
Land Preparation
First, the farmers were requested to draw a sketch map showing the direction where the land
is sloping, in order to select the site to build the runoff tank. They were also asked to mark
suitable place for growing crops, location of the house and the place where the annual and
perennial plants were already grown in the land.
Three methods of planting crops were introduced,
Ø One crop planted between contour bounds
Ø Mixed crops planted on the same contour
Ø N- Fixing trees (i.e. Gliricidia) planted on the contour
Together with farmers contour mapping of the land was done and advice was given, to
prepare the land accordingly. The nine farmers were grouped in to three and each group was
assigned a cropping method. Objective of this grouping was to measure the effectiveness of
each cropping methods separately.
Crops Recommended For Maha and Yala
In consultation with the farmers the project team recommended the cultivation of Long bean
(Vigna spp) Chillies (Capsicum spp) , Maize (Zea mays) and Brinjals (Solanum spp.) during
Yala. The farmers were provided with seeds and water required for the crops during the latter
part of the rainy season was taken from the run-off tank constructed in the bottom of the slope
In 2004 Yala season, farmers recommended to cultivated crops such as Snake gourd (Luffa)
Thibbatu (Solanum spp.) and Papaya (Carica papaya)
Rain Fall Measurements
Through out the research period rain fall was monitored using a rain gauge at one of the
households.
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4. Low Cost Rain Water Tanks
Surface runoff tanks were built at the bottom of the land towards the slope, where the runoff
rainwater flows across through the contours into the tank. Rainwater before it reaches the tank
flows through small field of grass grown near the mouth of the tank and then through a mesh
and finally through sedimentation traps. The traps are made in such a way, that the first step is
the widest and second and final steps being proportionately narrowest so, that the water
doesn’t rush into the well but flows slowly filtering the sediments.
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Constructed Ferro cement tanks were 5000 L (5 m ) in capacity and 190 cm deep with 210 cm
diameter (Diagram 01). Ferro cement was selected over brick tank as the cost of Ferro
cement tank is two third cheaper. The average cost of constructing a Ferro-cement tank was
Rs 7,500/- (US$ 75) at the time of construction i e. in year 2003 (excluding unskilled labour).
The beneficiary contributed in the construction by providing unskilled labour and local
construction material. Chicken wire mesh was used to reinforce the tank since it is cheaper
and available freely at the local market. Hand pump with a water meter was fixed to the tank to
measure the amount of water drawn. The tank was covered with either tar sheet cover or
polyethylene cover to prevent evaporation and developing algae through exposure to sun. To
prevent the breeding of mosquitoes in these tanks farmers were advised to grow fish as
predators.
The construction of the tanks was finished in June 2003 and collection of surface runoff water
started since then.
Two selected masons from the village were initially trained in construction of rainwater tanks.
These masons were used to build the tanks in the village.
210 cm
200 cm
Tar sheet or Diagram 1. Schematic
thatched cover 85 cm 3
structure of a 5m under
ground Ferro cement surface
Hand pump 190 cm
RESULTS AND DISCUSSION
Rainfall Pattern
The total rain fall received from June 2003 to July 2004 at Kurundankulama was 998mm. The
rain fall received during Maha (October - February) 2003/04 was 537mm, Yala (April - July)
2004 was 408 mm, intermittent (March) rain was 56.7 mm.
During the year 2003/04, the area received a Maha rain fall of 750 mm which was 28 percent
less than usual average rain fall. During Yala 2004 too, less rainfall was received than normal.
In fact whole of the district and the province faced a severe drought during this year.
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5. Water Collected and Extracted In Tanks
Table 2. Collection and usage of water in surface runoff tanks in both seasons
Names Maha 2003 Yala 2004
Volume of water Volume of water Volume of water Volume of water
3 3 3 3
collected in (m ) extracted (m ) collected in (m ) extracted (m )
Farmer 1 7.7 0.4556 2.1 2.0411
Farmer 2 7.12 0.049 8.6 3.2116
Farmer 3 4.71 2.46 4.5 1.8744
Farmer 4 2.83 0.0847 7.6 1.4768
Farmer 5 6.6 1.43 8.2 1.3105
Farmer 6 1.63 0.0501 5.8 2.5077
Farmer 7 5.46 1.32 2.5 2.9839
Farmer 8 5.99 0.2962 2.8 1.7507
Farmer 9 6.72 1.8747 3.4 3.0916
Total 48.76 8.0203 45.5 20.2483
Average 5.417 0.8911 5.055 2.2498
As shown in the Table 2., in early Maha season less water was extracted from the run off
tanks. This was due to the fact that the beginning of cultivation was done with rain water.
However, the tank water was used for cultivation during the latter part of the season when the
rain ceased. The availability of the water in the tank helped farmers to save not only their
annuals but also the perennial crops in their home gardens.
During Yala season due to the drought, farmers were depend on the harvested rainwater for
their cultivation. Extracted water for cultivation was more than double compired to Maha
season.
CROP AND INCOME
Maha season
When the total income of beneficiaries for the Maha season 2003 was compared with that of
2002, a marked increase in their income was observed. Prior to the project intervention the
average gross income of the beneficiary households was Rs.996/- where as in 2003 after the
project intervention the Maha income rose up to an average of Rs.2084/- thus doubling their
previous income (Table 3).
Yala Season
During 2003 Yala season before the project intervention, except farmer no. 9, none of the
farmers had cultivated any crops due to insufficient water. The profit of farmer 9 was
Rs.1250/- for 2003 Yala season.
In 2004 Yala season, after discussion with the farmers in the project group, seven of the
beneficiary group cultivated crop such as snake gourd, Lufa, Thibbatu (Solanum sp.) and
Papaya. Two of the farmers were sick during the Yala season and started cultivation later.
Farmer no. 1 and 4 used their collected rain water for brick making. Their income during this
period was Rs.7000/- and 9000/- respectively. Average Gross income of the seven farmers
who cultivated and sold their products by the end of the Yala season was Rs.622/- (Table 04).
Although the average income earned during the Yala season was less than the Maha season
2003, it was a considerable achievement that farmers started cultivate in Yala season too.
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6. Table 3. Crops Cultivated, land area, crop produce and income earned during Maha season in
2003
2002
Maha 2003 Maha Season
Season
Farmer
Income No. of Total
Cultivated Crop
(Rs)/ Acres Income Expenses
and produce
Season Cultivated (Rs)/Season (Rs)
Farmer 1 Long bean 29Kg 4275/- 1355/-
1350/- 1 Brinjals 260Kg,Chilli
1Kg Maize 300Kg
Farmer 2 1/2 Long bean 35Kg, 1335/- 170/-
1675/-
Chilli 37Kg,Maize 150
Farmer 3 1/2 Long bean 30Kg, 5033.50 1207/-
- Chilli 179Kg, Brinjals
46Kg, Maize 250
Farmer 4 1000/- 1/2 Long bean 13.5 Kg 3751.50 735/-
Chilli 52Kg, Brinjals
400Kg
Farmer 5 1 Long bean 53Kg 1595/- 712/-
750/- Chilli 20Kg, Maize
100 Kg
Farmer 6 1/4 Long bean 10Kg 180/- 483/-
600/-
Chilli 3Kg
Farmer 7 1/4 Long bean 5.5 Kg 150/- 205/-
-
Chilli 12.5 Kg
Farmer 8 1/4 Long bean 26Kg 1745/- 865/-
1000/- Brinjals 30Kg, Chilli
23Kg
Farmer 9 1/2 Chilli 18Kg Brinjals .691/- 513.50
600/- 11Kg Long bean
27Kg
Average 996.40 1/2 2084 694
Table 4. Crops Cultivated, land area, the produce and income earned during Yala season in
2003
Farmer 2002 Yala
Season 2003 Yala Season
Cultivated Crop & Total
No. of Income
Income Quantity Expenses
Acres (Rs)
(Rs)
Cultivated
Farmer 1 Lufa 20Kg, Thibbatu -
*
- 40Kg, Papaya 7000/-
*Rain water in tank used
for brick making
Farmer 2 1/4 Snake gourd 19Kg, Long 1225/- -
bean 9Kg, Pumpkin
51Kg, Brinjal 12Kg
Farmer 3 <1/4 Loofer 8Kg, Snake gourd 235/- -
5Kg, Thibbatu, Papaya,
Pumpkin
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7. Farmer 4 <1/4 Loofer,Thibbatu, Papaya 9000/-* 100/-
Rain water in tank used
for brick making
Farmer 5 1/4 Loofer 23Kg, Capsicum 1290/- 100/-
3Kg, Thibbatu, Papaya
Farmer 6 1/4 Loofer 12Kg , Thibbatu 260/- 78/-
Farmer 7 1/4 Loofer, Thibbatu, Papaya 118/- -
Farmer 8 1/4 Loofer, Thibbatu, Papaya, 185/- 130/-
leafy vegetables
Farmer 9 Rs1250/ 1/4 Loofer 8Kg, Pumpkin, 440/- 40/-
Papaya
Average 1/4 Rs. 622* Rs. 56
* excluding income gained from brick making
OUTPUT OF THE PROJECT
The contouring the land helped to direct water to the tank as well as to control erosion.
Planting of Gliricidia on the contour bunds provided mulch and N-fixing bacteria to the soil.
However, the benefit of gliricidia was not observed during the research period as the effects
are realized over a long period.
There was no significant difference of crop yields among the 3 cropping patterns used.
Longer term data is needed to observe any significant difference if there is any.
Two hundred percent of income increase was observed in Maha 2004 in compare with the
income prior to the project intervention.
Farmers started cultivated in Yala season too, due to the availability of water.
The water saved during Maha was a great asset to the farmers, as even during the Maha
season when the rain ceased earlier, the only way they were able to save their crop was by
using the water in the rainwater tanks.
Two trained masons are now been used by other projects to built Ferro cement tanks.
Discussion with farmers at the end of the project has indicated that bigger capacity tank such
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as 10m would have been more useful, especially since this Maha season rains ceased early.
REFERENCES
Annual Report, 2002. Samurdhi Authority, Ministry of Samurdhi, Sri Lanka.
Gould J and Nissen Petersen E, (1999).Rain Water Catchments Systems for Domestic Supply
Intermediate technology Publication Ltd. UK
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