Friday Nov 15, 2024
Friday Nov 15, 2024
Wednesday, 12 April 2017 00:00 - - {{hitsCtrl.values.hits}}
A couple of weeks ago I visited Polonnaruwa, travelling from Habarana road across the canal that transfers water from Minneriya Tank to Kantalai Tank and the canal was completely dry, indicating water received by Minneriya Tank from Amban Ganga was not sufficient. The fact was not surprising considering the unprecedented drought the country was facing.
Proceeding along I noticed Minneriya and Kaudulla tanks had some water, possibly replenished from recent rains. But arriving at Polonnaruwa I was pleasantly surprised to see Parakrama Samudraya brim-full with water, a beautiful sight. For a long time I had not seen the tank so full. The tank’s main water outlet, visible from the main road in Polonnaruwa town, was discharging water to paddy farmers.
Travelling along the several-kilometre-long tank bund of Parakrama Samudraya I noted the water level reached almost to the top of the tank’s spillway. A spillway is a structure common to every tank, large or small, generally concrete, allowing discharge of excess water. Over the concrete structure were steel spill-gates nearly three metres high (10 gates in all) and the water level was only six inches from the top. In a mild flood, excess water would flow over the spill gates, and depending on quantum of incoming water one or more gates could be opened a few inches or even full depending on the intensity of the flood.
I passed the tank and continued my journey along the Angammedilla canal bund, that supplies water to Parakrama Samudraya from Amban Ganga. The road at Angammedilla diversion takes a winding path over the two sluice structures. Adjacent to the road is a new bridge built across the two waterways, yet to be opened, possibly waiting for a politician. The question is, with less than 100 vehicles passing over a day, who needed the bridge?
Travelling half a kilometre inside the wildlife park one reaches the ancient Angammedilla sluice constructed by our ancient engineers taking advantage of the river bend. The ancient rock-filled sluice had been washed away, but part of the sluice still remains. The river water is currently diverted by a concrete dam built by the British. In heavy flows excess water passes over the sluice and the river continues, finally discharging into Mahaweli around 16 km away.
Travelling from Angammedilla along Kalugahawela-Bakamuna-Dambulla road one crosses the Elahera road, which runs on the bund of the ancient Elahera canal. The Elahera diversion draws water from Amban Ganga only two km downstream from Moragahakanda dam where the President inaugurated water filling on 8 January to coincide with two years of the new Government.
Elahera canal divides at Diyabeduma, supplying water to Giritale and Minneriya tanks. Water from Minneriya Tank through Yoda Ela supplies waters to Kaudulla and Kantalai tanks. When we came across Elahera canal, water was stagnant, indicating water was not diverted at the anicut, but sent downstream towards Angammedilla, resulting in Parakrama Samudra being full at the expense of others.
According to the Mahawansa, Elahera canal was constructed by King Washaba. The irrigation system includes a diversion structure constructed at Elahera across Amban Ganga (a tributary of Mahaweli Ganga), which starts from Matale foothills. This huge canal conveys water to Minneriya, Giritale, and Kantale reservoirs, also a large number of small irrigation tanks.
The first stretch from Elahera to Diyabeduma (where it bifurcates to Minneriya and Giritale) is 20.75 miles long. Further 2.50 miles, it enters Giritale tank and the other branch enters Minneriya. Giritale and the Kantale tanks were constructed by King Agbo (604 AD), but King Parakrama Bahu I had renovated the Giritale during the Pollonnaruwa era.
Minneriya Tank, built by King Mahasena (275-301AD), is equipped with two spillways. The north releases water to Kantale tank through Gal Oya. These irrigation works were rehabilitated by the British during 1903 and 1953.
How did Parakrama Samudra exclusively get water?
What surprised me was, how did Parakrama Samudra exclusively get water to the point of spilling over, while tanks fed by Elahera canal got nothing? In addition, Kalu Ganga receiving rains from eastern slopes of Dumbara discharges into Amban Ganga midway between Elahera anicut and Angammedilla. Last Maha season rains were a failure and paddy farmers who depend on rains suffered. Some rains arrived in late February and early March and brought some water to tanks. But Parakrama Samudra exclusively received water almost to spill-over, which indicates special treatment, depriving tanks fed through Elahera.
Normally, Maha rains arrive during the second half of September and farmers cultivate paddy fields in October that are harvested in January. But in mid-March farmers in Polonnaruwa were just beginning to harvest which would continue for a month, indicating fields were sown during December. Both Elahera canal and Parakrama Samudra received water from Amban Ganga for the past centuries. Did the officials treat them differently as the President originated from Polonnaruwa?
Moragahakanda dam is located on Amban Ganga nearly two kilometres upstream of Elahera diversion. During the construction of 
Moragahakanda, water flow was not disturbed but the drought reduced water to downstream tanks. When the President inaugurated filling of Moragahakanda on 8 January, downstream flow got stopped. Moragahakanda tank got filled very fast and TV stations showed animals trapped on islands and trees being rescued by the officials of the Wildlife Department.
The water filling continued for nearly six weeks and farmers downstream suffered, until water was released from Moragahakanda. It is clear that the released waters were given exclusively to Parakrama Samudra and tanks feeding from Elahera canal were denied. The filling of Moragahakanda tank was not only with collected rain water from northern slopes of Dumbara mountains, but included diverted Mahaweli waters from Bowatenna.
According to the Mahaweli Master Plan of 1958, the development of Mahaweli was to be implemented as three projects; (a) Polgolla Diversion, (b) Victoria – Minipe Diversion and (c) Moragahakanda Reservoir, to provide irrigation facilities to North and North-Central Provinces.
The implementation of Polgolla Diversion including Ukuwela and Bowatenna was completed during 1973-77, when Maithreepala Senanayaka (MS) was the Minister for Irrigation in the Sirimavo Bandaranaike Government. The Minister, originating from Medawachchiya, studied and married from Jaffna, was very much interested in Project C.
The J.R. Jayewardene Government, elected to power in 1977, modified the original program, dropped Moragahakanda, under an accelerated program completed dams and power plants at Victoria, Randenigala and Rantembe and the Right Bank Channel delivering water to Maduru Oya and System C, all in six years. These irrigation facilities are responsible for the country achieving near self-sufficiency in rice.
I discussed Mahaweli diversion with Dr. P.N. Fernando an engineer who was involved in the design and planning of the Mahaweli Project during the post-1977 era. According to him, Polgolla tunnel was built excessively large to divert maximum water to the north and Victoria was to be much smaller. During the redesign Victoria was enlarged to current 210MW generating capacity with provision for an additional plant of similar capacity on completion of Kotmale. In addition Rantembe dam and power plant was introduced.
Transfer of excessive water from Polgolla
The ability to divert excessive quantities of water from Polgolla was misused to supply excessive water to Kalawewa and to fill Anuradhapura group of tanks especially for the Poson season in June, supposedly for the benefit of pilgrims visiting Anuradhapura. But by June farmers have completed Yala cultivation. If this water was allowed to continue downstream it would have generated power at Victoria (210 MW), Randenigala (126 MW) and Rantembe (50 MW) power plants, whereas diverted waters at Polgolla could produce only 40 MW of power each at Ukuwela and Bowatenna power stations.
The original Moragahakanda scheme was meant to transfer water along a concrete lined NCP canal to satisfy the requirement of farmers north of Medawachchiya ending at Iranamadu Tank.
Maha cultivation normally commences in mid-October with rains arriving around 20 September and harvested in early January. Last Maha season rains disappointed farmers and most farmers cultivated in December, which were being harvested from mid-March. Then farmers would have needed most water during January/February period. But with the stoppage of water flowing in Amban Ganga to fill Moragahakanda, farmers were deprived of cultivation water. When water was released six weeks later, matured paddy did not require water. The question is, who planned the Moragahakanda filling?
Moragahakanda reservoir is capable of continuously delivering to Minneriya group of tanks and to Parakrama Samudraya. But delivering water to Kantale would require first filling of Minneriya tank. But tourism in Sigiriya/Habarana region heavily depends on witnessing the world famous ‘Elephant Gathering,’ the collection of elephants who feed on grass growing on the Minneriya tank bed when water edge recedes with usage. But if the tank remains continuously filled, there would be no grass for the elephants and tourists too would disappear.
Now, Moragahakanda has been filled (at least part), who would use the water? Moragahakanda water is supposed to be diverted north, but canal construction to deliver water northwards has not even commenced. According to the program the first section of the canal carrying Moragahakanda water near Anuradhapura would be complete only in 2024.
When Moragahakanda was planned during the 1960s, the tank was expected to deliver water northwards beyond Medawachchiya where the annual rainfall is less than 1,500mm per year. But the current plan which envisages issue of additional water to existing irrigation systems, as demanded by farmers and local politicians, would result delivering only one-tenth of Moragahakanda water to Iranamadu tank in Kilinochchi. That too would be in 2034 if all goes as per the program.
Mahaweli waters are diverted at Polgolla barrage through an eight km long tunnel capable of diverting 2,000 cusecs and generate 40MW of power at Ukuwela and join Bowatenna reservoir on Amban Ganga. Here 700 cusecs of water are diverted through a six km long tunnel, generating further 40MW of power, and continues in a trans-basin canal to Kalawewa and Rajangana reservoirs. The balance 1,300 cusecs flow down Amban Ganga and could be diverted into existing Elahera and Angamedilla and un-diverted waters joins Mahaweli and to the sea.
Meanwhile, un-diverted waters are stored in Victoria, Randenigala and Rantembe reservoirs which are capable of generating 386 MW of power, while diverted waters generate only 80 MW. Thus from a power generating point, best would be to divert least water at Polgolla. In addition, Victoria dam allows installation of a further power plant of 210 MW, which was expected after completion of Lower and Upper Kotmale reservoirs to stabilise water flow in Mahaweli.
For over a thousand years, Kalawewa supplied waters to paddy fields downstream, in addition supplied water through Yoda Ela to Anuradhapura tanks. In a similar manner Elahera and Angamedilla diversions delivered Amban Ganga waters to Minneriya group and Parakrama Samudra. During ancient times there was no Mahaweli diversion and farmers in both regions cultivated with available waters. The diverted waters were expected to be sent to north, the driest region of the country, while supplementing former two regions.
Since 1980 when Victoria power plants group became operational, for nearly 40 years Mahaweli waters were wasted under the diversion. During the very period Sri Lanka suffered with power cuts, CEB promoted non-moving Norochcholai and bought power from private power generators at massive costs. Polgolla water diversion and hydro-power plants were controlled by CEB engineers.
A few weeks ago the Daily Mirror reported that Nalaka Samarasinghe, an irrigation engineer, addressing a public awareness program organised by Elehera irrigation engineers informed that paddy cultivators in Sri Lanka used six acre feet of water for one acre of paddy during a season. This meant that 6,266 litres of water was used to produce one kilo of rice. He pointed out that according to the UN, only 3,450 litres of water was required to produce a kilogram of rice and excessive use of water warranted a better water management mechanism.
Similar warning was made during the planning stage of the Mahaweli Project in the late 1970s, the World Bank pointed out that Sri Lanka’s rice farmers consume the world’s highest volume of water for an acre of paddy cultivation and warned unless this consumption pattern is curbed, the entire Mahaweli Project would become a failure.
Accordingly, studies were carried out to ascertain the water requirement of paddy and researchers discovered that rice plants could grow without substantial loss of crop output, even when water is provided once in six days. Agriculturists proposed water be issued to fields every fourth day and the irrigation water distribution system for paddy fields in Mahaweli System C was designed accordingly. But farmers prefer to keep paddy fields inundated for weed control purposes, which consumes a huge quantity of water.
Massive wastage of water for 40 years
When Mahaweli was diverted in 1976, water was released to cultivate additional lands under Kalawewa (Mahaweli System H) and the balance was to be diverted to north of Anuradhapura, receiving lowest rainfall (under 1500mm annually) that were not facilitated under ancient irrigation systems. The trans-basin canal was expected to end at British-built Iranamadu tank near Kilinochchi.
At Polgolla 2000 cusecs of Mahaweli waters were diverted to Bowatenna and only 700 cusecs were transferred to Kala Wewa and balance of 1,300 cusecs (plus additional waters collected between Ukuwela and Bowatenna) was allowed to flow into Amban Ganga and to the sea for 40 years.
If the water diversion at Polgolla was confined only to requirement of Kalawewa, the balance 1,300 cusecs would have generated power at Victoria, Randenigala and Rantembe reservoirs with an additional capacity of 306 MW. Even today when the country faces the biggest drought and power crisis, waters continue to be diverted at Pogolla to be wasted. Since the 1990s CEB purchased power from Private Power Producers (PPP) to cover power shortages and most PPP contracts expired few years ago. CEB made use of the current drought to renew the agreements with PPPs.
Continuing the wastage of water was possible due to satisfying politicians by providing excessively high water to paddy farmers and filling Anuradhapura group of tanks for Poson pilgrims and now filling Moragahakanda tank and Parakrama Samudra to satisfy the President.
The massive wastage of waters for over 40 years by the CEB with the connivance of politicians has cost the county of billions of rupees, but also farmers got used to wasting precious water to the extent they use the highest quantum in the world and demand still more. The last Government modified the water distribution of Moragahakanda; will the current Government ever wakeup from their slumber to realise the massive wastage?
Sri Lanka is struggling to payback the foreign loans obtained for development projects, the main reason being the country’s inability to make full use of the facilities/resources delivered by the projects. Mahaweli project was expected to supply irrigation water to Kalawewa, majority water to be diverted to north and to generate hydro-power. When excessive quantities of water were diverted, hydro-power generation collapsed.
When so much water was wasted in Mahaweli for over 40 years, no organisation that was entrusted with the responsibility of ensuring proper utilisation of the country’s water resources raised alarm. Even our environmental organisations failed and only few citizens have complained of wasting precious water for political propaganda.
