HYDRAULIC ENGINEERING IN SRI LANKA
INTRODUCTION
What is Hydraulic Engineering?
Hydraulics -
In the simplest of explanations, it is the science that deals with the behavior of liquids in motion and at rest.
Liquids in motion produce forces whenever the velocity or flow direction changes, while at rest produce forces on devices submerged, in the form of pressure.
Hydraulic Engineering -
Is the branch of Engineering that deals with practical applications of using water and other liquids such as collecting, storing, measuring, transporting and regulating/controlling it. You need to make structures or devices, depending on the application, different in nature and in size, in order to use these naturally available resources in your favour.
The design of the Structures or Devices to make use of the water or liquids in the way we want it, depending on the application, requires a thorough understanding of hydraulic concepts and an equally good knowledge of the hydraulic principles.
History
Hydraulic Engineering in Ancient Sri Lanka- Beginning of Hydraulic Civilization
The recorded history of hydraulic engineering in Sri Lanka dates way back to 400 B.C. i.e. four centuries prior to the birth of the Christ (Pre Christian Era) or even much earlier. By the 1st Century B.C. ancient Sri Lankan engineers had mastered hydraulic engineering and the country accounts for one of the most glorious ancient irrigation systems in the world. Further today most renowned authorities in this field claims this as a sustainable water and soil conservation eco-system. This soil water eco-system was to maintain sustainable water levels in the environment and thereby to enhance the lives of not only human but all other living creatures like animals, birds, plants, etc. in the environs.
In meeting with the challenges of nature the ancient people were exposed to in Dry Zone having limited amount of water from rains only for three months during Northeast monsoon for their crops in growing population, paved way to a hydraulic Civilization that has no parallels in the world history.
The achievements of our hydraulic engineering centers around following features;
a. Tank building - Dam and embankments
Small - Abhayawewa (Basawakkulama) (Anuradhapura 220km from Col) – (4rd Cent. BC) - by King Pandukabhaya (377-307 BC),
- Tisawewa (Anuradhapura 220km from Col) (3rd Cent. BC) - by King DevanampiyaTissa (250-210 BC),
Big - Mahavilachchiya (220km from Col), Nochchipatana (220km from Col), etc. Elahera Divern Canal (220km from Col) (1st Cent. AD) - by King Vasbha (67-111 AD)
Big - Minneriya (220km from Col), Kaudulla (220km from Col), Huruluwewa (220km from Col) (3rd Cent. BC) - by King Mahasen (250-210 BC),
Big - Kalawewa (220km from Col) & Jaya Ganga Canal - (5h Cent. AD) –by King Dhathusena (455-473 AD),
- Giritale (220km from Col), Kantalai ((260km from Col) (7th Cent. AD) –by Agbo II (604-614 AD),
Sea - Parakrama Samudraya (300km from Col) - (12th Cent.AD) – by King ParakramaBahu
b. Intake Tower & Sluice– ‘Biso Kotuwa’ Invented 1st by Sinhalese
- Kandy Lake Bisokotuwa ( 120 km from Col),
Kattiyawa reservoir L/B Sluice Bisokotuwa - (200 km from Col) in Mahailuppallama (near Eppawala Mahaweli H-AreaKala Wewa Jaya Ganga Bisokotuwa (180 km from Col) – Modified
Preserved:
Parakrama Samudraya - Diversion Bisokotuwa
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c. Anicuts & Diversion Canals
- River diversion to Tanks -
Elahera Anicut & Diversion Canal 25 miles (40km) on Amban Ganga River (1st Cent. AD) – by King Vasabha (67-111 AD) - (220km from Col)§ Extension of Elahera canal to Minneriya, Giritale upto Kantalai – (1st Cent. AD) by King Agbo II (604-614 AD) - (220km from Col)
Angamedilla Anicut & Diversion Canal on Amban Ganga to Parakrama Samudraya (12th Cent.AD) – by King Parakramabahu (1153-1186 AD) - (300km from Col)
- Tank to Tank diversion - Yoda Ela (Jaya Ganga) 54 miles (90 km) from Kalawewa to Tisawewa (5th Cent. AD) – by King Dhathusena (455-473 AD) -- (220km from Col)
Precise Leveling of Canal first 17 miles 6 inches per mile ( 95 mm per 1 km).
- River diversion to Fields -
MInipe (Manimekhala) Anicut & Diversion Canal-(6th cent. AD)–by King Agbo I (571-604 AD) - (200km from Col)- River to another River -
Haththota Anicut & Yodayo Bendi Ela Diversion Canal on Kalu Ganga River- trib. of Mahaweli to Amban Ganga River and water thro’ Elahera to Rajarata (7th Cent. AD) –by Agbo II (604-614 AD) - (220km from Col)
d. 
Construction of Under ground canals and pipe systems
Construction of Under ground canals and pipe systems - To Ponds in Ranmasu Uyana Gardens in Anuradhapura from Tisawewa - (1th Cent. BC) – by King Vasabha (67-111 AD) -- (220km from Col)
- To Water Fountain Gardens from Sigiriwewa in Sigiriya -(5th Cent. AD) - Kashyapa (473-491 AD)-- (200km from Col)
Maduru Oya Ancient Sluice & Dam Discovered
( 260 km from Colombo on Mahiyangana, Dehiattakandiya, turn off at Aralaganvila)The discovery, of the ancient sluice and the dam in the recent past (in early 1980s) at Maduru Oya by Canadian construction engineers when they ended up selecting the same location using most modern engineering technology.
Therefore it is well worth a trip to these sites to witness yourself the splendor of the existence of one of the world’s foremost Hydraulic Civilizations in ancient Lanka and the beautiful serenity of the modern day Hydro Power complexes.
BISO KOTUWA’ – The ‘Valve-Pit’ and its Functions
1st in the World to invent ‘The Intake Sluice Structure’ - BISOKOTUWA (or The ‘Valve-Pit’) – by Lankans by 3rd Century B.C.By the 3rd century B.C. Sri Lankan engineers succeeded to be the 1st to invent the phenomenal intake sluice structure called BISOKOTUWA to regulate the outflow of water from contemporary large reservoirs successfully taming the vigours of forces exerted from the high pressures and velocities carried along with the releasing water without damaging the Bund. This is compared to the Valve-pit or Valve tower of the 19th Century European engineering by the English engineer Henry Parker. The method of regulating the flow of water from these tanks, was ingenious.
Functions of Bisokotuwa are of fourfold ( a Four-in-one unit):It serves as a surge chamber/tank - accomodates surges during opening & closing of gates in sluice, as a pressure & velocity reducer of releasing water by operating a lower water head than the reservoir, Gate retaining pit and water diverter allowing water to enter in one direction and to release on a another direction.
Gates:
Though any evidence regarding the Gates of Bisokotuwa has not been found as yet but one of the assumptions most accepted among the scholars about Gates is that they would have been made out of wood and controlled by a system of levers and would not have survived the nature.
Undersanding the Function of BISOKOTUWA in the context of modern hydraulic principles
If we apply the modern hydraulic principles, Bernouli’s theorem for the flow of water,
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V = C √2ghThe relationship is that velocity of the flow through a sluice is directly proportional to the square root of the water head of the reservoir.
Where,
V is the flow velocity,
h is the water head,
g is the gravitational acceleration which is a constant,
C is also a constant known as coefficient of velocity.
Accordingly, in high head reservoirs, the super critical velocity of the flow emanating from the sluice may be so great and it may lead to erode the downstream channel. Hence, the velocity has to be controlled to a manageable level.The Bisokotuwa provides a satisfactory solution to this problem. It consists of a chamber with a small inlet conduit and a relatively large outlet conduit. Due to the restriction of flow through the inlet conduit, the water level in the chamber is reduced to a lesser level than the reservoir. Since the water head in the chamber is now reduced, the flow velocity through the outlet conduit is also reduced. Further regulation is possible by providing gates to the inlet and outlet conduits. In some reservoirs, the chamber (Bisokotuwa) is located at further downstream position, i.e. centre of the dam section, which facilitate easy operation of the gates.
Now a days this feature is not in use in the modern reservoirs, since by now we have materials like concrete, which has a more resistance to erosion. The materials like brick, lime mortar etc. which were in use for irrigation works during ancient times, were highly vulnerable to erosion. A bisokotuwa which is still functioning with all its glory, can be seen in Katiyawa reservoir in Mahaweli system H area. (Katiyawa left bank sluice).
Hydraulic Engineering & Hydro Power in the Modern Era in Sri Lanka
The drift of the Kingdoms from Polonnaruwa in the Dry Zone to the southwest of the Wet Zone that took place around the 13th century AD due to the foreign invasions and disturbances, did no good to the flourishing hydraulic civilization. Since this drift in the mediaeval era up until the arrival of Portugese in 1505 AD, there is hardly any evidence available to testify a great deal of development in the works of hydraulic engineering. One reason is that the very nature in the Wet zone did not drive the people into a fresh thinking of engaging in hydraulics as the need for conserving water was minimal as there was plenty of rain and water was in abundance. Neither could we find any evidence during the colonial periods of Portuguese and Dutch, apart of the Dutch canal system in Colombo and suburbs as their interests were different, more focused on business. However the Dutch also have contributed with the construction of their canal system and if it be carefully analyzed it can be seen that they have had plans to extend the system from North-west Puthlam through Negombo as far south as to Kalutara and use it as a resourceful means of transportation, but apparently had not succeeded. But if it was realized it would have had a major share in contributing to the country’s economy by having low cost transportation system. English on the other hand, having stayed for a longer period moved inlands and discovered the ancient works while they cleared the jungles in search of land for the plantations and while some were in search of Elephant Tusks killing thousands of Tuskers. They renovated these structures and put them into operation but there were no new developments.
With the Industrialization in Europe the world became aware of the immense benefits of Electricity and it captured the number one place in development among all other forms of energy, even the former Soviet Union centered their revolution on a theme ‘Development by Electrification’ and gave it top most priority in their post revolutionary agenda.
Around Nineteen Forties (1940s AD), Sri Lanka was also feeling the need of having Electricity to develop the country and thereby uplift the livelihood of the people. By this time the British had already harnessed the potential of the possible streams which ran through some of their estates in the hill country and having them dammed, generated electricity through mini-hydro plants and had their individual Factories electrified which enabled to increase the production of mainly Tea significantly.
Hydro Power
At present we have 16 Hydro Electric Power stations in Sri Lanka with a total of 1205 MW installed capacity, out of which 3 (Inginiyagala, Udawalawe & Nilambe) are small hydro plants.
Kelani Valley Hydro Power Complex: (Commissioning from 1950 – 1982 AD) – 335 MW
The need of Electricity on a national scale to develop as a country was much felt at the brink of the Independence around 1947 and in the search for a locally available source of energy was on. The engineers found the country’s potential of hydro power was in plenty and in so plenty that they did not see a requirement to even search for any other sources of energy for decades in near future. The Engineer Mr.Wimalasurendra pioneered in this effort and all credit goes to him for the revolutionary introduction of the hydro electric power to the country first harnessing the potential of the two main tributaries of Kelani river, Kehelgamu Oya and Maskeliya Oya leaving the river Mahaweli to harness later. This far sited engineer steered the initial works around late 1940s by damming the Kehelgamu Oya at Norton (now called Norton Bridge reservoir) and first putting up a Power station, the so called ‘Construction Power Station’ as the name implies to take electricity for the construction of the first major station Laxapana (now Old Laxapana)at a very nominal expense. By 1982 AD i.e. nearly after 30 years, the Kelani Valley Complex had 5 hydro power stations in two cascades on the two tributaries having finally a total capacity of 305 MW of power completed of course in stages of time in meeting up with the growing demand in the country.
Cascade On Kehelgamu Oya:
1. 
Norton Bridge Reservoir - Old Laxapana Power House -50 MW – In 1950 - 112 km from Colombo
Norton Bridge Reservoir - Old Laxapana Power House -50 MW – In 1950 - 112 km from Colombo(6.3MW x03 Nos.+ 12.5MW x02Nos., Pelton Turbine) - Turn Off at Kalugala ( 98 km) on Colombo-Hatton road and 14 km further.
2. Caslereigh Reservoir – Wimalasurendra Power house -50 MW – In 1964 - 118 km from Colombo
(25MW x02 Nos., Pelton Turbine) - Turn Off at Diyagala Junct.( 108 km) on Colombo-Hatton road and 10 km further.
Cascade On Maskeli Oya:3. Laxpana Reservoir– Samanala- Polpitiya Power House -75 MW – In 1972 - 120 km from Colombo
(37.5MW x02 Nos., Pelton Turbine)
4. 
Canyon Reservoir (1st Arched Dam)– New Laxapana Power House- 100MW - In 1974- 128km, 124 km from Colombo
Canyon Reservoir (1st Arched Dam)– New Laxapana Power House- 100MW - In 1974- 128km, 124 km from Colombo(50MW x02 Nos., Pelton Turbine)
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5. Mausakele Reservoir & Canyon Power House– 60 MW– In 1978-1982 - 130km, 128km from Colombo
(30MW x02 Nos., Pelton Turbine)
Diagram of the Cascade please see below.
Hydraulic Engineering
Renaissance of the Hydraulic Civilization after Independance
Gal Oya & Udawalawe Projects:
It was only after the Independence in 1948 AD that a fresh thought was given by the newly elected Prime Minister D.S.Senanayake to revive the lapsed irrigation works who worked out plans and put them into action. It is not wrong to say that this was a rebirth or a renaissance of the hydraulic civilization and irrigation projects took off the ground launching Largest of the time Gal Oya irrigation Project around 1954 damming across the River Gal Oya at Inginiyagala which was completed in 1958. Inginiyagala is in the East of the country Dry Zone in Ampara District constructed a massive reservoir called Senanayake Samudraya ( Sea of Senanayake) named paying tribute to Late Primier D.S.Senanayake. Generates Hydro electric Power with small hydro machines totaling to 11MW of power.
Around the year 1970 Government launched yet another fairly large irrigation project in Udawalawe damming across the river Walawe which is in the dry Zone bordering the Wet Zone in the south. This also generates hydro electric power with small hydro machines totaling to 06MW of power.
1. Gal Oya Inginiyagala - Senanayake Samudraya & Hydro Power Plant – 11 MW– In 1954-1958 - 350 km from Colombo either on Ratnapura-Balangoda-Monaragala Road or Kandy-Mahiyangana-Mahaoya Ampara Road.
2. Udawalawe Reservoir & Hydro Power plant – 06 MW – 4 km long 36m high – In 1970-1976
170 km from Colombo on Rathnapura Pelmadulla, Timbolketiya turn off. Few kilo meters further to south you can have a bath in the natural Hot Water Spring near Suriyawewa another ancient irrigation site Urusitawewa where a Bisokotuwa also can be found.
The Mahaweli Irrigation & Hydro Power Scheme – 660 MW
Largest of all Irrigation Schemes:
Electric Power demand was ever rising and people had look for sources. Engineers were familiar that the potential of the longest and largest river Mahaweli stood untapped form its regions of origin in the hill country, the upper Mahaweli regions, and it had a huge potential for hydro power generation and the plans were on the table to harness the potential for irrigation with lot of Hydro power. A Master Plan was being prepared from 1960s.
Mahaweli Master Plan (prepared by UNDP-FAO team in 1968) was to irrigate 350,000 ha. (901,500 ac.) of land and to generate electricity to give around 600MW of power to the national grid on its way down to the irrigating lands which was to be completed in 30 years. It panned to construct a series of reservoirs in the Mahaweli Ganaga, its tributary the Amban Ganga which had been already diverted at two places by ancient engineers, Maduru Oya , Yan Oya & Malwathu Oya and the lands to be developed under 13 Systems which covered almost all Nothern part and most of the Eastern part of the country.
This plan implemented two trans-basin diversions of Mahaweli river one at Polgolla (Polgolla-Bowatenna Complex- started 1970 completed in 1976)and the other at MInipe(Victoria-Minipe Diversion). At Polgolla water is diverted to Kala Oya through Ukuwela Hydro power station generating 38MW of electricity and through Bowatenna reservoir left bank tunnel to Huruluwewa & Kalawewa through which to Anuradhapura city tanks, to Elahera-Minneriya-Kantalai system and Angamedilla-Parakrama Samudraya system through Bowatenna hydro power station generating 40MW of Electricity.
At MInipe water is diverted to Ulhitiya-Rathkinda reservoir and to Maduru- oya through the 30 km long Trans-Basin Canal which is the largest canal as well as the 1st canal to be concrete lined for the entire length which conveys water on a ‘water bridge’ called Aque-Duct to cross over the Badulu Oya river.
Major Structures in Mahaweli Sheme:1. Polgolla Diversion Barrage – 1970-1975 AD - 125 km from Colombo
Concrete Barrage - 146m long and 18 m High
10 Double leafed sliding wheel gated overflow type spillway.
Ukuwela Power Station - 38 MW - 1970-1975 AD - 146 km from Colombo
2. Bowatenna Reservoir & Hydro Power Plant – 40 MW - 1973-1976 AD - 171 km from Colombo
Two sectional Dams Embankment Dam– 93m long 29m high
Concrete Dam 226m long, 30mhigh
6 Radial Gated Spillway
3. Kotmale Dam & Hydro Power Plant – 201 MW - 1979-1984 AD - 160 km from Colombo
Rockfill with upstream Concrete Membrane Dam - 600 long, 87m high
3 Radial Gated Spillway
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4. Victoria Dam & Hydro Power Plant – 210 MW - 1980-1984 AD - 170 km from Colombo
Double Curvature Arch Concrete Dam - 520m long, 122m high
8 Radial Gated Spillway
5. Randenigala Dam & Hydro Power Plant – 126 MW - 1982-1987 AD - 185 km from Colombo
Rockfill with Clay Core Dam - 485m long, 94m high
3 Radial Gated Spillway | |||
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6. 
Rantembe Dam & Hydro Power Plant – 52 MW - 1987-1992 AD - 190 km from Colombo
Rantembe Dam & Hydro Power Plant – 52 MW - 1987-1992 AD - 190 km from ColomboConcrete Gravity Dam - 420m long, 41.5m high
4 Radial Gated Spillway
7. Minipe new Anicut and Trans-basin Canal to Ulhitiya - 200 km from Colombo
Concrete lined – 30m long
Aqua-Duct at Badulu Oya –Man made river (canal called Aqua-Duct) on top of a natural river.
It is called an Aqua-Dust because its shape is similar to a duct which carries water.
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Statistics
How the Hydro & Thermal Power Contribute to the Total Electric Power Generation in Sri Lanka over the Past 20 Years.
DATA
Electricity Generation of Hydro Power Plants in Sri Lanka –Averages 1997-2006
Hydro Plant | Installed Capacity | Energy Generation GWh/Year | Each System Contribution% to Total Hydro Generation | |||
Capacity MW | No. of Units | Total MW | Average Historic | Long Term Expected | ||
Kelani System | ||||||
Canyon | 30 | 2 | 60 | 137.7 | 178 | |
New Laxapana | 50 | 2 | 100 | 487.1 | 515 | |
Polpitiya | 37.5 | 2 | 75 | 400.7 | 466 | |
Wimalasurendra | 25 | 2 | 50 | 96.9 | 120 | |
Old Laxapana |  8.33 | 3 | 25 | 259.9 | 293 | |
12.5 | 2 | 25 | ||||
Sub Total | 335 | 1382.3 | 1572 | 39% | ||
Mahaweli System | ||||||
Kotmale | 67 | 3 | 201 | 376.4 | 502 | |
Ukuwela | 19 | 2 | 38 | 152.9 | 164 | |
Victoria | 70 | 3 | 210 | 559.6 | 886 | |
Randenigala | 61 | 2 | 122 | 274.3 | 494 | |
Rantembe | 24.5 | 2 | 49 | 156.3 | 246 | |
Bowatenna | 40 | 1 | 40 | 45.9 | 64 | |
Sub Total | 660 | 1565.4 | 2356 | 44% | ||
Walawe System | ||||||
Smanalawewa | 60 | 2 | 120 | 270.4 | 421 | |
Udawalwe -Small Hydro | 2 | 3 | 6 | 6.5 | 15 | |
Sub Total | 126 | 276.9 | 436 | 8% | ||
Kalu Ganga Syatem | ||||||
Kukule | 35 | 2 | 70 | 270.4 | 317 | |
Nilambe - Small Hydro | 1.6 | 2 | 3 | 8.9 | N/A | |
Sub Total | 73 | 279.3 | 317 | 8% | ||
Gal Oya | ||||||
 Inginiyagala - Small Hydro | 2.475 | 2 | 5 | 26.5 | N/A | |
3.15 | 2 | 6 | ||||
Sub Total | 11 | 26.5 | 0 | 1% | ||
1205 | 3530.4 | 4681 | ||||
Average historic for period 1997 - 2006 | ||||||
Annual Electricity Generation - Total System in GWh
YEAR | Mahaweli System | % Cntrib | Kelani & Other Hydro | % Cntrib | Thermal | % Cntrib | Total Gneration | |
1984 | 517.3 | 136.6 | 653.9 | |||||
1985 | 987.8 | 40% | 1384.9 | 57% | 70.5 | 3% | 2443.2 | |
1986 | 1279.1 | 48% | 1355.8 | 51% | 6.4 | 0% | 2641.3 | |
1987 | 844.8 | 31% | 1339.4 | 49% | 524.3 | 19% | 2708.5 | |
1988 | 1361.6 | 49% | 1235.1 | 44% | 199.5 | 7% | 2796.2 | |
1989 | 1474.2 | 52% | 1325.4 | 46% | 52.6 | 2% | 2852.2 | |
1990 | 1724 | 55% | 1421.2 | 45% | 3.8 | 0.1% | 3149 | |
1991 | 1535 | 45% | 1585.1 | 47% | 260.9 | 8% | 3381 | |
1992 | 1561.3 | 45% | 1282.3 | 37% | 640 | 18% | 3483.6 | |
1993 | 1909.9 | 53% | 1536.2 | 42% | 186 | 5% | 3632.1 | |
1994 | 2210.2 | 51% | 1880.5 | 43% | 275.2 | 6% | 4365.9 | |
1995 | 2663.4 | 56% | 1846.8 | 39% | 269.3 | 6% | 4779.5 | |
1996 | 1808.5 | 42% | 1421.2 | 33% | 1123.3 | 26% | 4353 | |
1997 | 1620.7 | 33% | 1823.7 | 37% | 1463.6 | 30% | 4908 | |
1998 | 1951.8 | 35% | 1956 | 35% | 1660.3 | 30% | 5568.1 | |
1999 | 2111.6 | 35% | 2036.9 | 34% | 1921.5 | 32% | 6070 | |
2000 | 1546.5 | 23% | 1606.3 | 24% | 3531.3 | 53% | 6684.1 | |
2001 | 1409.1 | 22% | 1409.1 | 22% | 3478 | 55% | 6296.2 | |
2002 | 1160.2 | 17% | 1425.5 | 21% | 4204.5 | 62% | 6790.2 | |
2003 | 1429.9 | 19% | 1758.3 | 23% | 4429.8 | 58% | 7618 | |
2004 | 1045.1 | 13% | 1709.4 | 21% | 5293.8 | 66% | 8048.3 | |
2005 | 1256.2 | 14% | 1914.6 | 22% | 5538.4 | 64% | 8709.2 | |
2006 | 2123.9 | 23% | 2166.1 | 23% | 5073.2 | 54% | 9363.2 | |
Avg 85-06 | 1591.6 | 36% | 1610.0 | 36% | 1827.6 | 27% | 5029.1 | |
STD | ||||||||
MAX | 2663.4 | 56% | 2166.1 | 57% | 5538.4 | 66% | 9363.2 | |
MIN | 844.8 | 13% | 1235.1 | 21% | 3.8 | 0.1% | 2443.2 | |
Avg 85-89 | 1189.5 | 44% | 1328.1 | 50% | 170.7 | 6% | 2443.2 | |
Avg 85-94 | 1488.8 | 47% | 1434.6 | 46% | 221.9 | 7% | 2443.2 | |
Avg 97-06 | 1565.5 | 23% | 1780.6 | 26% | 3659.4 | 50% | 7005.5 | |
Avg 02-06 | 1403.1 | 17% | 1794.8 | 22% | 4907.9 | 61% | 8105.8 |
The Expansion of Hydraulic Structures during the Ancient Hydraulic Civilization
TYPE | TIME | KING | STRUCTURE | WORLD |
Small Tanks 543 B.C. (Arrival of Aryans) –1st Century B.C. Anuradhapura Period | 5th Century B.C. | Village Chief | Village Tanks | |
4th Century B.C. | King PANDUKABHAYA (437-367 B.C.) | Abhayawewa Tank (Basawakkulama) Jayawewa Tank | ||
3th Century B.C. | King DEVANAMPIYATISSA (250-210 B.C.) | Tisawewa Tank WalaswewaTank (Karachchavapi) | ||
2nd Century B.C. | King SADDA TISSA (137-119 B.C.) Brother of Dutugemunu | Pelivapi, Samanavapi, Talattavapi,Kulumbarivapi,Viharavapi, 18 Tanks | ||
Medium Tanks 1st Cent. A.D.. –3rd Cent. A.D. | 1st Century A.D. | King ILA NAGA ( 33 - 42 B.C.) | Tissa Wewa, Dura Tisa Wewa | |
1st Century A.D. | King VASABHA ( 67 – 111 B.C.) | Mahavilachchiya Tank, Manaketiya,Nochchipotana,Hiriwadunna, Kaali,Mahavaapi + 11 Tanks Elahera Anicut & Diversion Canal + 12 Canals | ||
Large Tanks 3rd Cent. A.D.. –10th Cent. A.D. | 3rd Century A.D. | King MAHASEN ( 274 - 301 A.D.) | Minneriya Tank, Kaudulla wewa, Hurulu wewa,Maminiya, Maagalla,MahaGal Kadawala,Niramulla, KaalaPasaana vapi, Hulugalla, Mora wewa + 16 Tanks; Pabbathenna Canal + small Canals | |
4th Century A.D. | King UPATISSA ( 365- 406 A.D.) | Topawewa + 6 Tanks | ||
5th Century A.D. | King DATHUSENA ( 455 - 473 A.D.) | Kalawewa Tank, Balaluwewa, Madatugamawewa,Manamattawewa, AakattiMurittuwewa, MahaaPabbatawewa + 18 Tanks; Yoda Ela (Jaya Ganga) | ||
King KASHYAPA ( 477 - 495 A.D.) | Sigiriya Water Gardens, Water Fountains, Underground water piping from sigiriya wewa | |||
6th Century A.D. | King MUGALAN II ( 531 - 551 A.D.) | Nachchaduwa wewa (Pathpahan), Padawiya wewa( Danawvaapi), Garitharavaapi | ||
6th Century A.D. | King AGBO I ( 571 - 604 A.D.) | Mamaduwa wewa, Kurundu wewa, SiriwaddaManaka wewa,Thattimurippukulam wewa; Minipe Anicut, Minipe Diversion Canal | ||
7th Century A.D. | King AGBO II ( 604 - 614 A.D.) | Kantalai Tank (Gantalawewa), Giritale wewa, Haththota Anicut, Minipe Diversion Canal Extention | ||
Large Tanks 3rd Cent. A.D.. –10th Cent. A.D. Polonnaruwa Period | 11th Century A.D. | King MAHA VIJYABAHU ( 1055 - 1110 A.D.) | BuduGuna wewa, Renovation works | |
12th Century A.D. | King MAHA PARAKRAMABAHU ( 1153 - 1186 A.D.) | Parakrama Samudraya (Sea of Parakrama), Panda wewa,Baana Samudraya; Angamedilla Anicut & Diversion Canal, Gothami Canal, Kalinga Anicut & Diversion Canal, Ridibandi Anicut & 2 other Anicuts at Deduru Oya | ||
King NISHSHANKA MALLA ( 1187 - 1196 A.D.) | Paandi Vaapiya + Renovation works |
