Mahaweli Ganga Basin by Engr. S. Arumugam,Mahaweli River by Chanaka Wickremasuriya

Extract from Water Resources of Ceylon by Engr. S. Arumugam 1969

60. MAHAWELI GANGA BASIN

 

The Mahaweli Ganga is Ceylon's largest and longest river. It drains an area of 4.034 sq. miles which is nearly one sixth of the area of the island. Its length is 207 miles. It has its sources in the Central highlands and drops nearly 8,000 ft. to flow into the sea at Koddiyar Bay, South of Trincomalee. The Dik Ova which has its source in Marlborough Estatc~-elevation 4,500 ft. and Dambagastalawa Oya, Agra Oya and Nanu Oya from the Ambawela hills, Horton Plains and Pidurutalagala respectively Call above 7 000 ft.) are the four streams that form the Ganga. Dambagas-talawa Oya flows into Agra Oya and these two streams meet Nanu Oya at Talawakelle to form Kotmale Ova which is one of the largest tributaries of the Mahaweli Ganga. Dik Oya meets Kot-male Ova at Mahavilla and from their confluence the river is called Mahaweli Ganga. The pheripheral length of the watershed boundary is 400 miles and water divides separate this river from the Walawe Ganga, Kirindi Oya, Kelani Ganga, Maha Oya, Deduru Oya, Kala Oya and Maduru Ova.

Land Use and Potential

The Mahaweli Ganga basin consists of distinctive natural regions having characteristic soil types, topography, climate and land use potential. The high lands in the wet zone are well developed with tea, rubber and cocoa on the hill slopes and with paddy in the valleys, but there is verv little development in the lower basin.

The existing land use pattern* in the basin is given below:

 

Land Use	Extent Acres	Percentage
1.     Urban	7,520	0.3
2.     Homestead gardens	172,580	6.7
3.     Rubber	32,380	1.3
4.     Tea	357,20	13.9
5.     Paddy	177,430	6.9
6.     Other Permanent Cultivation	84,450	3.3
7.     Shifting cultivation	364,700	14.9
8.     Forest	1,131,190	43.9
9.     Grass Land & Scrub	180,760	7.0
10. Unused Land	15,530	0.6
11. Water & Marsh	50,450	1.9

 

Total                                                                 2,574,710             100%

*Taken from the Report on Survey of the Resources of the Mahaweli Ganga

Basin. Part I by the Hunting Survey Corporation Ltd,

 The above table shows that 65% of the area of the basin, mostly in the plains, is yet available for development.

Existing major irrigation development schemes in the basin consist of:

Name of Scheme	Extent Benefitted Acres
1.     Badulu Oya Scheme	2500
2.     Sorabora Wewa Scheme	1300
3.     Damparawa Wewa Scheme	1100
4.     Mapakada Wewa	300
5.     Bathmedilla Scheme	14000
6.     Allai Scheme	14325
7.     Minneriya Tank	14100
8.     Giritalle Scheme	4400
9.     Parakrama Samudra Scheme	18150
10. Elahra Scheme	4800
11. Kaudulla Scheme	10230
12. Minipe Extension Scheme	10460
13. Hathtota Amuna	600
14. Nalanda Oya Reservoir Diversion Scheme	Nil

Paddy is cultivated in all these lands.

 

Hydrology

The source of the Mahaweli is in the hill country Wet Zone and hence it has two flood peaks and two dry spells. The 820 sq. miles of its catchment area which is in the wet zone experiences heavy rainfall, the highest mean annual fall being 218 inches at Watawala.

'The balance catchment area of 3,214 sq. miles is in the dry zone where the average annual rainfall varies between 55 to 80 inches.

The average annual run-off of the Mahaweli excluding the 600,000 acre feet diverted annually at Minipe, Elahera and Angamedilla anicuts is 7,900,000 acre feet. The mean annual discharges at some points along the river are:

at Peradeniva1,680,000 ac. ft.

at Gurudeniya1,935,000 ac. ft.

at Randenigala2,951,000 ac. ft.

at Weragantota4,206.000 ac. ft.

at Manampitiya6.360.000 ac. ft.

 

The flood cycles in the Mahaweli basin coincide either with the North East or South West Monsoon periods. Major floods were recorded in June 1888, October 1906, December 1913, July 1932, May 1933, May 1940, August 1947 and December 1957. The largest recorded flood experienced in the upper reaches of the river was in August 1947, the flood peak at Peradeniya railway bridge at 2.30 p.m. on the 15th August 1947 was 180,000 cusecs.

 

Flood peak periods in the lower Mahaweli do not necessarilv coincide with that of the upper reaches. In the upper section the river flows mostly through a deep and rocky river channel while the lower portion torms the flood plain. The biggest flood experienced in the flood plain was in December 1957 when the flood peak flow at Manampitiva on the 26th of December was estimated as 514,950 cusecs. The railway embankment at Manampitiva acted as a weir and the flood waters spilled over it for a length of 21,500 ft Also the Weragantota Rest House which was under 3 ft. of water for the August 1947 floods, was almost completely submerged except for the ridge of its roof.

Water Resources of the Maior Tributaries:

The Mahaweli Ganga has numerous tributaries, the main para-metres of the larger ones are:

 

Name of Tributary Stream	Catchment Area	Length 112mls	Drop in feet	Q Ac.ft x 103
1.     Kotmale Ova	226.0	43.3	5500	845
2.     Uma Ova	283.0	46.5	5985	520
3.     Badulu Ova	152.0	37.5	3394	305
4.     Loggal Oya	101.5	28.3	3711	269
5.     Heppola Ova	47.6	22.0	4220	70
6.     Ulhitiva Ova	170.5	38.5	811	138
7.     Hulu Ganga	97.3	18.5	3900	300
8.     Hassalak Ova	46.0	130.0	4250	126
9.     Heen Ganga	49.7	17.6	5583	218
10. Amban Ganga	573.5	77.1	4100	1165
11. Kalu Ganga	107.0	25.0	2775	265
12. Kaudulla Ova	196.0	35.0	517	136

 

Almost all the major irrigation schemes in the area are fed by the tributarv streams. All these schemes are ancient works restored and improved in recent times and reflect the efforts and the skill of the ancient engineers to harness the water resources of the Mahaweli Ganga.

 ----------------------------------------------------------------------------------------------------

From the Sunday Island of  5th September, 2021 - Part 1 

Mahaweli at Mahiyangana

The Mahaweli

 “Mahaweli mahaweli mahaweli”….. Virtuoso Pandit Amaradeva’s classic resonates out there as the author traces this river; geographically, along the topographical contours of this varied land, and historically, along its intricate relationship with this island’s both ancient and contemporary civilizations.

The Mahaweli, or literally ‘the great sands’, is not just a river. And it is not just the island’s longest river (at 335km), or the one with the largest river basin (10,500 of the island’s total 65,000 sq km). The Mahaweli has a natural uniqueness to it that has resulted in a profound bearing on the formation and evolution of our cultural and political heritage. It will not be presumptuous to say that this river, analogous to its meandering trace, has carved the path for the history of this island’s peoples. Or even perhaps, been responsible for the sheer existence of a history itself. Amaradeva poetically alludes to this in his classical ballad.

One can say that the Mahaweli traces its headwaters to the Kotmale Oya and Hatton Oya. The former, having its source along the north western slopes of the Horton Plains plateau, while the latter traces its beginnings along the Watawala ridge. The significance of this will not be lost to even the amateur hydrologist. An overlay of the rainfall patters of Sri Lanka on her map shows that the country’s highest annual average rainfall takes place along this range, and notably, on account of it being fed by the more prolific South West Monsoon, at almost twice the precipitation of its North East counterpart.

This makes for a remarkable fact. The Mahaweli becomes, as far as this author can ascertain, the only Dry Zone river to be fed by the South West Monsoonal rains.

Having harnessed and coalesced these waters, the Mahaweli carves an idyllic path northward along the Gampola valley. The splendor of this valley discernible to even this author, as he once sat at a hermitage on the hills of Hindagala watching this river, dotted on either side by quaint hamlets and rice fields, the vestiges of an ancient kingdom that found refuge during trying times. And alas only to be told by his mentors that he was negating the benefits of his vipassana endeavors by pleasing his senses!

The river thus meanders its way up to Gannoruwa. And here, the providence of nature, or the hands of the formative deities of this land, depending on your preference, make a call. The river encounters a small hillock at Gannoruwa, and perhaps because of it, and unlike like all rivers originating on the western slopes that carve their way down toward the western seaboard, the Mahaweli makes an abrupt right turn.

At some point in pre-history these waters would have then encountered a formidable bridge of Charnockite rock in the escarpment between the central plateau and the southern edge of the Knuckles massif. Eons of hydrological erosion then forced these waters through the gorges of Randenigala and the breathtakingly narrow Rantambe, churning out what would have then been class four and five rapids. Legend has it that the master equestrian King Rajasinghe II would leap across the narrow 20-foot gap on his trusty steed, and that until more recently when the dams of the Mahaweli Development Program took shape, the sounds of these churning waters could have been heard over five km away. Like a giant hydrological serpent, the river breaks through this East-West divide to rear its head onto the eastern half of the island. And here too the seemingly inexplicable takes place.

Having garnered further waters from the Knuckles via the Hulu Ganga, from Pidurutalagala via the Ma Oya, from Horton Plains via the Uma Oya and from even as far as the Badulla and Passara hills via the Badulu Oya and Loggal Oya, instead of finding what would look to the layman as a path of least resistance directly toward the eastern seaboard, the Mahaweli decides to turn north.

The river then traverses this almost directly northern path, covering about half of its total distance, and a third of the island, to break into the ocean via a myriad of mangrove forested deltas at the island’s largest bay at Koddiyar in Trincomalee. Here too merging into yet another natural wonder of what is one of the world’s largest natural harbors, replete with underwater chasms and gorges of over 700m deep. But not until the river has harnessed even greater waters along the way through its largest tributary, the Amban Ganga, it too a creation of the western slopes of the Knuckles range, and the less plentiful Hasalaka Oya and Heen Ganga, which gather waters off the range’s eastern slopes. In this section the Mahaweli creates what is the country’s largest deposits of alluvial soil, spanning the entirety of its northern trajectory and breaking into vast areas of up to 10km wide on account of seasonal flood plains, as well as the largest seasonal sand banks from which the river derived its name.

Thus, it is as if nature was the precursor to our island’s proud hydrological engineering heritage, and even its modern manifestation of the Mahaweli Development Program. For nature seems to have decided long ago to find a way to harness the bounty of water from the island’s salubrious western slopes and nourish its dry north-central and eastern plains. A feat of engineering even modern man would have found hard to, and is yet to, replicate.

But the story of the Mahaweli does not end there. Mankind soon pounces upon this natural marvel to both exploit and tinker with her resources for their benefit. It is akin to having been endowed with a mythical nature’s guitar, and then fine tuning its cords to seek the perfect tune. The resulting dance having spanned over two millennia yet continues. While this story could be arguably best narrated through time, this author will choose to deliver it, like the river itself, along the course of its journey.

The story begins in the upper reaches of the Kotmale Oya, the Agra Oya. Here, literally and metaphorically shrouded in the mists of the Thotupola hill and time, a little south of Pattipola, are the remnants of a little known 220m long tunnel and 11km long canal. Believed to have been constructed circa the 13-14th century, it is perhaps the earliest known subterranean trans basin canal. Considered an engineering marvel for its time, this canal used to divert the west bound waters east into the Uma Oya basin to irrigate the lush fields of the Uva.

Moving down the Kotmale Oya, further nourished by the Nanu Oya is the Upper Kotmale Reservoir and Hydro Power scheme. The third largest power generator of the Mahaweli Development Scheme originally conceived between 1965-69 under and FAO/UNDP funded master plan, this was one of the last to be completed in 2010 after a series of environmental controversies and re-engineering. The river is then joined by the waters of the Devon Oya, Pundal Oya and Ramboda Oya and flows into the famed and beautiful valley of Kotmale, once the sanctuary of the legendary King Dutugemunu during his youth. This valley was inundated by a rock-filled dam 87m high and 600m in length starting in 1978 under the Accelerated Mahaveli Development Program, becoming the second highest hydro electricity generator of the scheme. Its added function being controlling the flood waters of the Gampola valley and optimizing the diversion flow at the barrage at Polgolla.

As the Mahaweli, now as a fully-fledged river or ganga, meanders its way around the upper middle-class suburbs of Kandy, evoking visions of our checkered history with names like Primrose Gardens, Anniewatte and Mawilmada, we encounter the Polgolla Barrage. Polgolla was the first of the projects under the Mahaweli Development Program and was implemented in 1976. At 144m in length and 14.6m in height, a relatively innocuous looking structure compared to its gargantuan brethren, the Polgolla Barrage nevertheless, in this authors view, creates the most geographically impactful diversion of Mahaweli waters.

It starts with an eight km long underground penstock northward to Ukuwele power station. Ukuwele then releases these spent waters into the Dhun Oya, which in turn connects to the Sudu Ganga which then emerges further north as the Bowatenna Reservoir. Built in 1981, the picturesque Bowatenna’s primary purpose was retention and diversion of waters for irrigation. In a bizarre twist of engineering and geographical fate, the released waters of Bowatenna become the Amban Ganga, making the Mahaweli the only river to feed its own tributary.

Waters diverted from Bowatenna are channeled through a tunnel to Lenodara, and from there enter the Dambulu Oya. It is from here that modern man’s diversions of the Mahaweli start to enter the realm of the ancient kings, and their stupendous feats of hydrological engineering and civilization building.

The Dambulu Oya has a little known but unique history, as it is a conduit of Mahaweli waters from two separate modern and ancient diversions. The ancient system starting from Demada Oya, a tributary of the Amban where an anicut built by Dhatusena diverted waters to the Wilimiti Oya, a tributary of the Dambulu. The Dambulu Oya thus takes Mahaweli/Amban waters from both Dhatusena’s creation as well as the modern Bowatenna, via the Ibbankatuwa Tank, north into the gigantic Kala Wewa – Balalu wewa complex and the Kala oya basin. Dhatusena’s “only treasure” as he proclaimed, for which he earned his patricidal son Kassapa’s wrath, Kala Wewa is the largest tank complex of ancient Sri Lanka and was built in the fifth Century AD. Waters from the Kala Wewa are transferred via the famous Jaya Ganga, carved also during the same time with the intricate engineering precision of a gradient of one foot to one mile, 86km to Devanampiyatissa’s third Century BC Tissa Wewa in the ancient citadel of Anuradhapura. Waters also find their way to the more modern Rajanganaya further west via the Kala Oya itself. The excess waters of the Tissa wewa find their way into the Malwatu Oya, the islands second longest river, and off that via the Yoda Ela into the famed Giant’s Tank over 50km north west of Anuradhapura, it too a creation of the legendary Dhatusena, to irrigate the famous Rice Bowl of Mannar.

A bifurcation at Dambulu Oya built in 1976 also takes Mahaweli waters into the ancient and touristically popular Kandalama tank, the origin of which is little known, as well as to the Hurulu Wewa a further 25 km north. Built by Mahasen in the first Century AD, the Hurulu is the primary repository source of Sri Lanka’s fifth longest river, the Yan Oya, where a new reservoir was constructed in 2017 about 50km further north east. Sporting what is Sri Lanka’s longest main and saddle dams totaling a staggering six km in length, the Yan Oya project infuses water into the ancient Padaviya Tank. Originally built to trap the waters of the Ma Oya, the actual origins of this very ancient tank are yet debated but speculated to having been built by Saddhatissa (137-119 BC). 165km from its original diversion at Polgolla, this will be the furthest point north yet traversed by the Mahaweli’s waters.

But Bowatenne is not done yet in her generous dispersions of Mahaweli’s bounty. Rather coincidentally and poignantly perhaps, situated at what is considered the center of the island, the reservoir stands where the iconic Nalanda Gedige temple stood. Since relocated to the banks of the lake, this temple represents a unique fusion of Hindu and Mahayana Buddhist Tantric architecture and is thought to have been built around the 13th Century. Waters thus blessed flow beyond Bowatenna as the mighty Amban, the Mahaweli’s largest tributary, which has an ancient and contemporary history worthy of her own story.

From the Sunday Island of 19 September, 2021- Part 2

Mahaweli's Ultimate Gift Can Unite The Nation

Downriver of Bowatenna along this river is the spanking new Moragahakanda reservoir, the 

latest and last of the ambitious Mahaweli Development Program projects. Completed as

recently as 2018, Moragahakanda also comprises of the Kalu Ganga reservoir scheme. 

The latter, completed at the same time and originating deep in the recesses of the Knuckles

range, is itself a tributary of the Amban. The waters of this reservoir are nevertheless diverted

via a 12 km long tunnel to Moragahakanda as the confluence is downriver of the dam

Hattota Anicut. This is a 30km diversion built by Agghabodhi in the seventh century to divert 

waters to the famous Elehara canal down river of the Moragahakanda Dam. Having harnessed

these waters from the Kalu Ganga, as well as from the Thelgamu Oya, the Moragahakanda 

reservoir is being earmarked for a further ambitious effort via the Upper Elehara Canal Project

(UECP) currently under construction, to transfer waters via South Asia’s longest irrigation tunnel

at 28 km and a further 65 km of canals to the Mahakandarawa, Manankattiya tanks and again to 

the Hurulu Wewa.

In parallel is the construction of the North Western Province Canal Project (NWCP), which will

tap into an outlet from Lenodara and carry Mahaweli waters via a series of tanks and 78km of 

canals into the Mi Oya and Deduru Oya basins. These two river basins are both replete with

ancient irrigation networks of their own, spanning from pre-Vijayan times to Parakramabahu in 

the late 10th Century. Like a giant octopus whose tentacles are gradually encasing the island, 

these two canal projects will thus complete the Mahaweli’s western most encroachment.

Literally yards below the Moragahakanda dam along the Amban lies the iconic Elehara anicut 

and Yoda Ela canal. Remnants of the original stone dam built by Vasaba in the first century, 

increased in height by Mahasen in the third, likely restored by Parakramabahu in the 10th are

still visible today. The diversion was slightly relocated as the canal was restored by the British

during the early part of the 20th century.

The Kalu Ganga reservoir harbors a little known yet now defunct and inundated secret of the

The waters thus diverted travel along the picturesque Yoda Ela, originally also built by Vasaba,

over 30 km to the Minneriya (Mahasen third century) and Giritale (Agbo seventh century) tank 

complexes. Water is further transferred from Minneriya to the larger Kaudulla tank, also 

attributed to Mahasen, but steeped in legend as actually a construct of his estranged sister. 

Princess Bisobandara, banished from the palace for her love of a commoner.

Waters from Kaudulla then find their way to the Kantale (Gantala) tank, built by Agghabodi in 

the seventh century, and the spent waters of this system finally find their way into the 

Tampalakamam bay in Trincomalee, a little north of the Mahaweli’s natural estuary in Koddiyar,

and 95 km as the crow flies from the commencing diversion at Elehara.

As the Amban, after its confluence with the Kalu, continues as the western and northern 

boundary of the Wasgamuwa National park, it makes its final bequeathment to this island’s 

ancient and modern civilization at Angamadilla. Originally built by Upatissa around the fourth 

century, along with the Akasa Ganga canal to divert waters to the Thopawewa, the prolific 

Parakramabahu enhanced both dam and canal to amalgamate five existing tanks and create 

and feed the great ‘Sea of Parakrama’ or Parakramasamudraya, considered the largest of the

 ancient world’s reservoirs.

Having thus exhausted itself, the Amban continues further east to eventually coalesce with its 

great benefactor the Mahaweli at the southern border of the now aptly named Flood Plains

National Park.

But our story must now double back to where we stepped off the great river at the Polgolla 

barrage. After this remarkably significant diversion, the Mahaweli meanders its way through 

the salubrious suburbs of the historic city of Kandy, into the now inundated Teldeniya valley. 

And here it emerges at what is probably the jewel in the crown of the modern Mahaweli 

Development Scheme: Victoria.

A gigantic double curvature dam standing 122 m tall and with a crest length of over half a 

kilometer, it was mostly funded by a grant by her Majesty’s government in 1978. Coincidentally 

and perhaps suitably named in recognition of both the Royal bequeathment and the submerged

Victoria falls, the dam’s primary function, with 722 m cubic meters of storage, is delivering an 

installed capacity of 210MW of hydro power, the highest of all along the Mahaweli system, and 

capturing and regulating waterflow for the myriad of irrigation schemes further downriver.

Twenty km downriver from Victoria is the equally impressive Randenigala Dam. Completed a 

few years after the former with German engineering, Randenigala, though a rock filled dam of 

only 90m height and a crest of 300m, nevertheless creates the largest reservoir in the Mahaweli

scheme at over 860 m cubic meters of storage capacity and has an installed hydroelectricity 

capacity of 120MW.

Under 3 km downriver from Randenigala, straddling the famous Rantambe gorge, is the small 

Rantambe dam creating a reservoir of 21m cubic meters and an installed capacity of 52MW. 

Just below this dam the Mahaweli once again embarks on a generous dispersion of its wealth,

 instigated by both ancient and modern man.

On the left bank lies the ancient Minipe anicut. Originally built by Dhatusena in the fifth century,

 extended by Agghabodhi in the sixth to around 22 km, and thought to have been further 

extended a staggering 78 km by Sena II in the ninth century all the way up to Angamedilla, 

the weir of the modern Minipe is currently being further raised to divert even greater volumes of

Mahaweli waters into what is known as the Mahaweli E system, one of the many agricultural 

zones labeled with alphabetical nomenclature along the modern Mahaweli scheme.

On the right bank, directly opposite the ancient Minipe anicut lies the ‘new’ Minipe anicut and 

the modern Loggal Oya canal. Running 30 km up to the Ulhitiya and then Ratkinda reservoirs, 

these are feeder tanks that eventually carry Mahaweli waters through a five km long tunnel to

the legendary Maduru Oya reservoir, to feed the largest resettlement systems of B & C of the

Mahaweli scheme.

Still shrouded in debate and mystery as to its origins, the Maduru Oya dam is famous for the 

revealing of its ancient sluice upon modern man’s survey and excavation for the optimal site f

for a new reservoir. Dated to the first century BC, and thought to have been constructed by 

Katukanna Tissa, further excavation and analysis of earthen works speculates that the original

dam may have pre-dated Vijayan times. The modern Maduru Oya reservoir, sporting a surface

 area of 6,400 acres, is only second to the giant Senanayake Samudra in Gal Oya, and harbors 

an inland fishing industry replete with idyllic fleets of colorful sailing outriggers.

Having dispersed a considerable share of its wealth, and finally stepping off the central 

highlands, the Mahaweli now continues its journey from Rantambe north along the great flat

lands of the northeast. Past the sacred city of Mahiyangana, its literal translation meaning

 ‘flat land’ in ancient Pali, the Mahaweli now enters the natural wonders of National Parks and 

Wildlife Reserves. All legally constituted as part of the accelerate Mahaweli Development 

Program starting in the early 1980s, these parks, though now the purview of its denizens of 

herds of wild elephant, mugger crocodiles and white bellied sea eagles, still harbor the secret 

relics of an ancient relationship between the river and its people.

Approximately 55 km north of Mahiyangana along the Mahaweli lie the Dastota Rapids and 

Kalinga Island. Now part of the Wasgomuwa National Park, and the first of a series of large

 islands along the Mahaweli, legend has it that Kalinga, with its gigantic hardwood trees, was 

the repository of a great ship building industry from which ships were launched and navigated

 to sea.

While the island is littered with little explained monolithic ruins, ancient narratives and 

topographical evidence also speak of two spectacular canals, one on each bank just above the

 rapids that nourished fields and habitats far beyond. On the left bank are the remnants of the

 Kalinga Yoda Ela. Allegedly built by Dhatusena, it merged with, and with some spectacular 

engineering ingenuity, crossed the Amban at a weir downriver of Angamedilla and carried water

 over 50 km north to nourish the fields as far as Kaudulla.

On the right bank are the remains of the Gomathi Ela, built by Mahasen; it carried waters over 

40 km to the Maduru Oya basin. Thus, Mahaweli waters had long been utilized for the 

nourishment of a civilization that the modern system has only begun to replicate in the late 20th

 century.

Further down river, about half-way through the Flood Plains National Park, the Mahaweli enters 

a controversial zone of its geological history. Aerial photographs, and now with the benefit of 

online satellite imagery, show the faint trace of a dry riverbed to the west of the current trajectory.

 This trace runs approximately 25 km before re-joining the current path of the river.

The famed Somawathiya Chaitya lies adjacent to this dry river, on its eastern bank, but now well

 toward the west of the current river. Chronicled to have been built by Kavan Tissa circa second

 century BC of the Ruhunu Kingdom in recognition of his sister Princess Soma, and whose 

kingdom bordered the Mahaweli, it gives further credence to the fact that the river has likely 

changed course over 2,000 years ago.

But the historical civilizational consequences of this are profound and speculatively mysterious.

 Closer scrutiny at the possible trajectories of the river show that the original course would have

 crossed what is the current trajectory at almost right angles, both just a little north of the 

Somawathiya temple, as well as closer to the sacred site.

Given the hydrological power of the flow, this author will postulate that the ancient Mahaweli, 

prior to its change of course, would have contributed a greater volume of perennial water to both

 the Verugal Ara as well as the Kandakadu Ara, two branches of the Mahaweli that veer off to the

 east at the exact site of these crossings.

These two waterways, while today barren and dry during most of the year, save for a seasonal 

man-made sand bagged barrage at Kandakadu, would have, over 2,000 years ago, carried a 

far greater volume of water into what is Gangapahalawela, Angodavillu, Mavil Aru and the Allai 

tank in Seruwawila.

These names and the areas they refer to evoke legends, folklore, and cryptic references in

 chronicles of ancient irrigation networks and an ancient thriving kingdom in and around today’s 

Serunuwara and Somapura. The jungles of Somawathiya Sanctuary today are replete with

 scattered ancient ruins, mostly undocumented, un-referenced and likely yet undiscovered giving

 further evidence to the existence of a kingdom of this island’s history that is largely unknown, 

and more importantly for this narrative, the Mahaweli’s likely contribution toward it.

The Mahaweli, along the remainder of its northern journey, meanders through large flood plains,

 where evidence lies of historical seasonal usage of their alluvial soils, as well as modern efforts

 of trapping some of these seasonal floods into man-made lakes such as Janaranjana Wewa a 

little south of Sooriyapura. North of the Allai-Kantalai Road, the Mahaweli starts to break up into

 mangrove wetlands and numerous deltas prior to breaking free into the ocean at Koddiyar bay.

But the story of man’s dalliance with the Mahaweli has not ended here. The second phase of the

 North Central Province Canal Project is to carry the Mahaweli’s water all the way up to the 

Northern Province to Iranamadu, the island’s northern most tank. Perhaps again on the back of 

ancient tanks and channels built by Mahasen (Kalnadinna), Vasaba (Thannimurippu) and

 Agghabodhi (Vavunilkulam), the waters of the Mahaweli will reach this ultimate destination.

May be then this island will be finally united. Not just from north to south, but across class and

 caste, language and philosophy, and political partisanship. Hopefully driven by a newfound 

sanity among its denizens yet symbolically attested to by the waters of the Mahaweli.

(Concluded)