A public lecture delivered at Institute of Engineers, Sri Lanka (IESL) on 6th November 2019 at CEB Conference Hall

1. Ancient Water Resources Management in Sri Lanka
P.B. Dharmasena, 0777-613234, 0717-613234
dharmasenapb@ymail.com, dharmasenapb@gmail.com
https://independent.academia.edu/PunchiBandageDharmasena
https://www.researchgate.net/profile/Punchi_Bandage_Dharmasena/contributions
http://www.slideshare.net/DharmasenaPb

2. CONTENT
• Multipurpose water management in ancient Sri Lanka
• Water management master plan
• Ancient water based city planning
• Shortage of water or wastage of water?
• Tank cascade systems: The first agricultural heritage in Sri Lanka
• Traditional tank-village ecosystem
• Ancient rainwater harvesting – Evidence from Pidurangala

3. Multipurpose water management in ancient Sri
Lanka
Water management was of multi-purpose:
• Food production – irrigation;
• Human needs – settlement, drinking water, bathing, recreation, other
domestic needs;
• Rainwater harvesting systems;
• Existence of the environment (flora, fauna, environs);
• City planning (Anuradhapura, Sigiriya)
• Parks, landscaping etc. (water springs, ponds)
• Administrative boundaries
• Natural disaster mitigation (Flood, drought, cyclone, epidemics)

4. Water Management Master Plan of Sri Lanka
Country level
Inter-river basin level
Inter-reservoir level
Sub-watershed level
Village level
Field level

5. Kevesastha (Northern)
Upulwangiri
Rakungiri
Mahagiri
Chalaka
Neelagiri
Kawasthalabha
Dhumaka Kaddeera Indra
Agni

6. Kevesastha (Northern)
Upulwangiri (Kala Oya)
Rakungiri (Malwathu Oya)
Mahagiri (Samanala mountain area)
– Kelani, Kalu, Walawe, Mahaweli
Chalaka (Mi Oya)
Neelagiri (Modaragam Aru) Kawasthalabha (Yan oya)
Dhumaka Kaddeera (Deduru Oya)
Indra (Maduru Oya, Mundeni
Aru, Gal oya)
Agni (Kumbukkan Oya,
Menik Ganga, Kirindi Oya

7. • Inter-river basin water resources
sharing
• Dambulu Oya - Malwathu Oya
diversion canal (860 AD)
• Malwathu Oya - Kanadara Oya
diversion canal (860 AD)
• Yoda Ela - Nachchduwa feeder
canal (540 AD)
• Inter-reservoir water resources
sharing
– Kalawewa - Thisawewa Yodha
Ela (470 AD)
– Nachchaduwa - Nuwarawewa
feeder canal (290 AD)
– Balaluwewa -
Siyambalangamuwa feeder
canal (290 AD)
– Basawakkulama - Maha
Vilachchiya feeder canal (470
AD

8. Sharing water resources in the past
(600 BC – 1200 AD)
• Inter-river basin water
resources sharing
• Dambulu Oya -
Malwathu Oya
diversion canal (860
AD)
• Malwathu Oya -
Kanadara Oya
diversion canal (860
AD)
• Yoda Ela -
Nachchduwa feeder
canal (540 AD)
Mahakanadarawa
Nachchaduwa
Kalawewa-Balaluwewa
Dambulu oya
Malwathu oya
Kanadara oya
Kala Oya

9. Manewa cascade
Mahakanumulla cascade
• Single bank canal
• It runs along contour
• Water is collected from upstream
• Water is released to both sides
• Canal moves along tank upstream
• Tank cascade systems are fed
Kalawewa-Thisawewa Giant Canal

10. April – May 2010
“Inconvenient Truth” behind
Engineering Designs of
Irrigation Projects developed
during the Last Century.
“……….Those days we thought
that the canal was planned to
avoid rock barriers as the ancient
people did not own the
technology to break them
……..”
- Eng. Mahinda Panapitiya

11. • Inter-reservoir water
resources sharing
– Kalawewa -
Thisawewa Yodha Ela
(470 AD)
– Nachchaduwa -
Nuwarawewa feeder
canal (290 AD)
– Balaluwewa -
Siyambalangamuwa
feeder canal (290 AD)
– Basawakkulama -
Maha Vilachchiya
feeder canal (470 AD)
Kalawewa-Balaluwewa
Thisawewa
Siyambalangamuwa
Nachchaduwa
Nuwarawewa
Mahavilachchiya
Basawakkulama
Malwathu oya
Thalawa oya
Kala oya
Sharing water resources in the past
(600 BC – 1200 AD)

12. It could be the city plan of
Ancient Anuradhapura kingdom
Mystery of Star gate

14. Jethawanaramaya
Ruwanwelisaya
Thuparamaya
Abhayagiriya
Lowamahapaya
Ancient water based city
planning (Anuradhapura)
Isurumuniya
Jayasrimahabodhi
Mirisawetiya
Inner
City

15. Water culture in Anuradhapura Kingdom
• Water cordon around the kingdom (Thisawewa, Nuwarawewa,
Basawakkulama, Bulankulama)
• Focused to enrich groundwater in the kingdom
• Paddy lands under these tanks are relatively low
• Catchments are not adequate
• Tanks are fed by an adjoining river basin
• Alluvial soil is found due to Malwathuoya and Halpanoya
• How these gigantic structures could be sustained?
• Hard bedrock to trap groundwater (granitic gneiss සහ charnockite
gneiss)

16. Gaminiwapi (Bulankulama)
Abhayawapi (Basawakkulama)
Thisawewa
Nuwarawewa
Perimiyankulama
Thuparamaya
Jethawanaramaya
Abhayagiriya
Ruwanwelisaya
LowamahapayaMirisawetiya
Source: Thusitha Wagalawatte et al 2015
Charnockite gneiss
Granitic gneiss
Quartzite

17. Granite Charnockite

18. Ponds, water cordons, water tunnels and wells are scattered in the
kingdom to replenish and monitor groundwater

19. Cities being sunk due to depletion of groundwater table
1. Beijing in China by 11
cm/ year
2. Mexico by 28 cm/ year
3. Jakarta by 28 cm/ year
4. Bangkok by 12 cm/ year
1
2
3
4

20. Annual average rainfall: 2,000 mm
Land extent: 65,610 km2
Total volume of water: 131.22 bil. m3
Discharge to sea: 66.18 bil. M3 (>50%)
No. of river basins: 103
Major reservoirs and dams: 80
Small tanks: 14204
Small anicuts: 12,942
Source: N. Eriyagama et al 2015
Shortage of water or wastage of water?

22. River basins – Water losses to Sea
River Basin Total Basin
Area (km2)
River
lengths
(km)
Total Rainfall
(million m3)
Drainage to Sea
(million m3) %
Deduru Oya 2,616 142 4,794 1,608 34.0
Kala Oya 2,772 148 4,424 587 13.0
Malwathu Oya 3,246 164 4,592 568 12.0
Yan Oya 1,520 142 2,269 300 19.0
Kelani Ganga 2,278 145 8,692 5,474 62.0
Gin Ganga 922 113 3039 1903 62.0
Kalu Ganga 2,688 129 10,122 7,862 77.0
Walawe Ganga 2,442 138 9,843 2,165 22.0
Mahaweli Ganga 10,327 335 26,804 11,016 41.0
Meeoya 1,516 109 2,176 338 16
Shortage of water or wastage of water?

23. River Basin Total Basin
Area (km2)
River
lengths (km)
Total Rainfall
(million m3)
Drainage to Sea
(million m3) %
Kalu Ganga 2,688 129 10,122 7,862 77.0
Source: Dept. of Agrarian
Development
Major reservoirs: 0
Minor tanks: 3

24. River Basin Total Basin
Area (km2)
River
lengths (km)
Total Rainfall
(million m3)
Drainage to Sea
(million m3) %
Kelani Ganga 2,278 145 8,692 5,474 62.0
Source: Dept. of Agrarian
Development
Major reservoirs: 2
Minor tanks: 9

25. River Basin Total Basin
Area (Km2)
River
lengths
(km)
Total Rainfall
(million M3)
Drainage to Sea
(million M3) %
Gin Ganga 922 113 3039 1903 62.0
Source: Dept. of Agrarian
Development
Major reservoirs: 0
Minor tanks: 0

26. River Basin Total Basin
Area (km2)
River
lengths
(km)
Total Rainfall
(million m3)
Drainage to Sea
(million m3) %
Deduru Oya 2,616 142 4,794 1,608 34.0
Major reservoirs: 4
Minor tanks: 2408
Source: Dept. of Agrarian
Development

27. River Basin Total Basin
Area (km2)
River
lengths
(km)
Total Rainfall
(million m3)
Drainage to Sea
(million m3) %
Malwathu Oya 3,246 164 4,592 568 12.0
Major tanks: 05
Minor tanks: 1731
Source: Dept. of Agrarian
Development

28. River Basin Total Basin
Area (km2)
River
lengths
(km)
Total Rainfall
(million m3)
Drainage to Sea
(million m3) %
Walawe Ganga 2,442 138 9,843 2,165 22.0
Source: Dept. of Agrarian
Development
Major/ medium reservoirs: 12
Minor tanks: 750

29. River Basin Total Basin
Area (km2)
River
lengths
(km)
Total Rainfall
(million m3)
Drainage to Sea
(million m3) %
Kala Oya 2,772 148 4,424 587 13.0
Major reservoirs: 3
Minor tanks: 1015
Source: Dept. of Agrarian
Development

30. River Basin Total Basin
Area (km2)
Total Rainfall
(million m3)
Drainage to Sea
(million m3) %
Yan Oya 1,520 2,269 300 19.0
Major tanks 2
Small tanks 746

31. Source: Dept. of Agrarian Development
River Basin Total Basin
Area (km2)
Total Rainfall
(million m3)
Drainage to Sea
(million m3) %
Mee Oya 1,516 2,176 338 16.0
Major tanks 1
Small tanks 750

32. Network of tanks
and streams
No flood and no
drought
Malwathuoya
Kalaoya
Yanoya

33. Nachchaduwa
Kanadarawewa
Vilachchiya
Kalawewa and
Balaluwewa
Huruluwewa
Network of tanks and streams in the form of cascades

34. Tank clusters or cascades
Hydrology based definition
• A ‘cascade’ is a connected series of tanks organized within a micro-catchment (meso
catchment) of the dry zone landscape, storing, conveying and utilizing water from an
ephemeral rivulet’. – Madduma Bandara, 1985
Ecology based definition
• Tank cascade is an ecosystem,
where water and land resources
are organized within the micro-
catchments of the dry zone
landscape, providing basic needs
to human, floral and faunal
communities through water, soil,
air and vegetation with human
intervention on sustainable basis’.
– Dharmasena, 2017

35. Distribution of tank
cascades in Sri Lanka
Main factors:
1. Morphology (landscape)
• Lower elevation,
• Moderate undulation
2. Rainfall
• Bimodality
• ~1500 mm/ year
3. Soil and geology
• Regolith aquifers
• Low infiltration
• RBE – LHG

36. Tank clusters or cascades

37. Tank clusters or cascades

38. Sanitary places of
women and kids
Sanitary places of men
Faeces as a nutrient source to paddy fields
Tank-village system has been declared now as a
Globally Important Agriculture Heritage System (GIAHS) by UN
A Self sustained System based on precise management of water

39. Godawala
Perahana
Gasgommana
Iswetiya
Tank water – no pollution, no sedimentation: safe drinking water, good storage

40. Landa
Thisbambe
Gangoda Kattakaduwa
Kiul-ela
Paddy field - no salinity, good fertility: High productivity

41. Therefore, I suggest it is essential to probe deeply the awakening of ‘Sri Lankan Water Culture’
not only through a physical/ engineering point of view but also on the basis of a spiritual
dimension.
When we attempt to study the creations made by a human society nurtured in a spiritual environs
by using only physical and environmental principles we may understand only a fraction of it.

48. Sigiriya kings
must had been in
need of clean
drinking water

50. Evidence of a
huge explosion
Not a natural
decay

51. Rainwater flow
pitch (convex)

62. Balancing Stone

63. So called
balancing
stone

64. Finally ……….
The platform area of Pidurangala rock is about 2 ha. If it is
assumed that 80% of monthly rainfall could be collected from
this flow pitch, the volume, which could be stored monthly is:
Months Jan. Feb. Mar. Apr. May Jun. Jul. Aug. Sep. Oct. Nov. Dec. Total
Rainfall
(mm) at
75%
probability
30.3 12.6 26.0 87.7 31.8 3.1 3.4 4.4 25.9 132.0 168.3 105.7 631.2
Runoff (m3) 485 202 416 1,403 509 50 54 70 414 2,112 2,693 1,691 10,099

65. • According calculations at least 10,000 m3 of water can be
collected from this system.
• What does it mean?
• This historical perception can be rejected as a myth.
• However, this system if rehabilitated will supply annual
water storage of 10,000 m3 to the people, who are living
around and are threatened with the chronic renal disease
with unknown aetiology.
Then …..

66. • If the daily drinking water requirement is 3
lits./head, the problem of annual drinking
water requirement of 9,000 people can easily
be solved

67. Multi-disciplinary approach is
required to study the ancient multi-
purpose water resources management

68. Sri Lankan
Water
Heritage
Hydrologist
Anthropologist
Architect
Geologist
Archaeologist