Mahaveli waters: Power and irrigation conflict

The Mahaveli Development Project was planned in the late 1960s as a multi-purpose project to provide water for irrigation and for enhancing hydropower generation. At that time the politicians boasted of exporting electrical power to India.

Implementation of the project on a 30-year programme commenced in the early 1970s under the Sirimavo Bandaranaike Government, as the ‘Diversion of Mahaveli Waters to North’. She was able to complete Polgolla Diversion, Ukuwela Power House, Bowatenna Tunnel and Power House, improvement of Kalawewa and associated works.

J.R. Jayewardene’s Government, which came into power in 1977, modified the project into the ‘Accelerated Mahaveli Scheme’ compressing the 30-year programme into a mere six years. Under the World Bank guidance, having successfully negotiated funding from different countries, the Government was able construct the Victoria, Randenigala and Rantembe dams and power houses, right bank channel to divert water to Maduru Oya Reservoir and irrigation works for settlement of farmers and complete the project generally on schedule.

Power generation capability

Sri Lanka’s current power generating capacity is given as:

Kotmale (Upper and Lower): 351 MW

Diverted from Polgolla: 80

Victoria to Rantembe: 386

Laxapana Group: 335

Samanalawewa: 124

Others: 92

Total hydropower: 1,368 MW

Of the island’s total hydropower capacity, contribution from Mahaveli River (Kotmale to Rantembe in above), amounting to 817 MW, Kelani River (Laxapana, etc.) provides 335 MW. Thus, Mahaveli River is the foremost contributor to hydropower.

Thermal power: Current thermal power generating capacity is divided between:

CEB owned: 876

Privately-owned: 835.5

Total thermal: 1,711.5 MW

In addition small hydro projects produce 201 MW, solar power 13 MW and bio energy and wind power 15 MW, making a total installed capacity of nearly 3,300 MW.

Irrigation water from Mahaveli

During the mid 1970s, with the construction of the Polgolla Dam, part of the Mahaveli waters were diverted, generating electric power at Ukuwela and Bowatenna Power Houses and waters continued to fill Kalawewa and Rajangana Wewa, which feed other tanks for irrigation purposes.

Kalawewa, built by King Dhatusena, was in existence for over 1,000 years, storing rainwater for the paddy farmers. With the diversion of the Mahaveli waters, Kalawewa storage capacity was enhanced and additional paddy lands were opened under the Rajangana Scheme and other minor tanks.

Waters that continue along Mahaveli without diversion, after power generation at Victoria, Randenigala and Rantembe, are diverted again via Right Bank Channel to Maduru Oya Reservoir for distribution to Mahaveli Systems A, B and C.

During the early 1980s when farmers were settled under System C, by J.R. Jayewardene government, which happened to be in the Eastern Province, Tamil politicians vehemently protested that the Tamil-dominated Eastern Province’s demography is being changed by settlement of Sinhala people and the settlement had to be stopped. The commencement of communal problems in 1983 put a stop to further colonisation.

Power from Mahaveli

Diverted waters at Polgolla produce 40 MW of power each at Ukuwela and Bowatenna Power Stations and balance waters continue to fill and generate power at Victoria (210 MW), Randenigala (126 MW) and Rantembe (50 MW) reservoirs and respective power plants, constructions completed in the early 1980s and utilise the same water in cascading generating plants.

While diverted waters at Polgolla produce a total of 80 MW of electric power, non-diverted waters are capable of producing 386 MW of power. Based on power generation only, diverted water’s capacity to produce power is less than 20% of total. Thus for the production of electrical power, most effective would be to divert only 20% of the water at Polgolla, allowing 80% of water to be used for power generation.

Warning from World Bank

During the planning stage of the Mahaveli Development 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 Mahaveli Project would become a failure.

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 Mahaveli System C was designed accordingly. But the farmers prefer to keep paddy fields inundated for weed control purposes, which consumes a huge quantity of water.

Paddy cultivation practices

Village level paddy farmers at the cultivation committee meeting agree on a cultivation programme, which prescribes a period for release of water from tank and farmers are expected to prepare the fields and sow their seed paddy by the agreed date.

Normally in Anuradhapura area, Maha rains commence around 15 September and prior to the rains the fields are dry and hard, where field bunds damaged due to machinery running over during harvesting and transport.

Rains soften the ground and after the first rains farmers repair the damaged field bunds, the second and third rains collect water in the fields and ploughing is made possible. Historically, rain water collected in the tanks was reserved for Yala cultivation and when the rain waters are insufficient the deficiency is supplied from tanks.

Currently ploughing and preparation of fields for paddy is totally done with machinery, requiring less water and time. Therefore the release of water for land preparation can be reduced and further reduction is possible with the use of rain water. If a farmer is unable to complete his land preparation in time, he could always use a shorter maturing variety of rice and still harvest with the other cultivators. Therefore it is possible to reduce usage of water for paddy cultivation without a reduction of output.

Electricity generation vs. irrigation

Mahaveli Development Scheme was a project to provide water for irrigation as well produce hydropower for the country and has given rise to conflicting demands of water requirements from the two sectors. The scheme was completed with borrowed funds and principle and interest need to be settled by the country. For the project to be a success, balance need to be reached in optimum usage of both sectors.

From the time ancient kings built irrigation tanks in the dry zone, farmers were supposed to cultivate Maha season with rain water, collect and store rain water in tanks for issue during dry months. Similarly the diverted water needs to be utilised prudently without wastage.

But in reality, Kalawewa is kept substantially full with diverted water almost all the time and for the best part of the year, the Victoria reservoir remains practically empty, producing only a small fraction of the electricity it is capable of generating. A situation that exists even today. If Victoria Reservoir was kept filled instead of Kalawewa, there would have more power production from the same quantity of water due to enhanced water head at the generators.

Surely, in the planning stages of Mahaveli Diversion Project, Engineers would have identified the sufficiency of water in the Mahaveli River for irrigation as well as power generation; otherwise all these expensive structures and power-plants would not have been planned.

Wastage of water

During the planning stage of the Mahaveli Development Project, there would have been certain allocation of water to each reservoir, to get optimum usage from rainfall. But due to various influences, greater quantity of water is being diverted to the north. Few realise that most of the diverted water are being wasted and are at the cost of power generation through Victoria, Randenigala and Rantembe Power Plants, who were supposed to use the same water in cascading generating plants.

With the normal rainfall, irrigation tanks which were supposed to collect and store rain water, lack the storage capacity, as they are already full with Mahaveli waters, spill over creating floods. This happened in late 2010 and early 2011 where flooding happened on three occasions, even in April 2011 during the height of normal dry season Rajangana Wewa spilled over. No one seems to care about sheer wastage of water and the decline in power generation.

Malwathu Oya, flowing through the Anuradhapura town, discharges waters to the sea at south of Mannar. For over 1,000 years the waters of Malwathu Oya were diverted to feed Giant’s Tank close to Mannar, located in the driest sector of the country.

Most of the catchment area of Malwathu Oya is the Anuradhapura District. Also the rains as well as excess water discharged from paddy fields from Anuradhapura West and Rajangana areas flow into Malwathu Oya. The wastage of water from paddy cultivation is so high, that on number of occasions during the past few years, Giant’s Tank too spilled over due to excess water.

Victoria Stage II

The Victoria Project was planned to be completed in two stages and the Stage I was completed in early 1980s as a British aid grant, with a power generating capacity of 210 MW and the Stage II was to enhance power generation capacity by further 210 MW. Stage II was to be implemented after the completion of Kotmale Dam, which was expected to store and regulate flow of water in the upstream Mahaweli River.

The originally proposed Victoria Power Plant Stage II has been overlooked for some decades for unknown reasons. But the subject re-appears periodically in various documents. In a document titled ‘Preparatory Study for Environmental and Social Considerations’ dated 25 October 2007, accessible over the Internet, the environmental aspects of the project are discussed.

The proposed Stage II will include construction of an additional tunnel and generators capable of adding 210 MW of power to the national grid at a cost of US$ 222 million, which could substantially reduce power generation expenditure with expensive imported fuels. Non-implementation of Victoria Stage II remains a mystery.

The continuous wastage of water from Mahaveli over the years, gave the impression that the water quantity flowing is insufficient for the full power production even at the current Victoria Stage I power station. When Mahaveli water is insufficient for Stage I, how can anyone even suggest Stage II which was supposed to add further 210 MW into national grid?

Get back to basics

When Victoria Stage II was planned to enhance hydropower by further 210 MW, planners were well aware of the sufficiency of water in Mahaveli River for cultivation purposes as well power generation. As the World Bank officials noted in late 1970s, water needs intelligent distribution between irrigation and power for the best interest of the country. World Bank staff observed our farmer cultivation practices and warned prudent usage of water is a pre-requisite for successful implementation of Mahaveli Project.

After all such warnings the Mahaveli Authority and the CEB should have been more careful and should bear the responsibility for having diverted most of the water and filled up Kalawewa, sabotaging power production in Victoria and other plants down the line.

Over the years we have never witnessed any propaganda requesting farmers not to waste irrigation water. The claim that insufficient water for the full power production at Victoria Stage I is a fabrication created by some officers of CEB.

What needs to be done is to control and reduce diversion of water to Kalawewa and fill up Victoria Reservoir, so that maximum power could be generated from Victoria, Randenigala and Rantembe power plants. The issue of irrigation water to cultivators be controlled and the farmers in the country and in Anuradhapura area in particular need to be educated on the optimum use of rain water, control and prudent use of water from irrigation tanks.

Now with the country’s self sufficiency in rice, the farmers could be encouraged to cultivate more subsidiary crops as chillie and maize, which consume less irrigation water, especially on marginal lands.

Who benefited

When additional quantities of Mahaveli waters were diverted to Kalawewa, who benefited from the issue? Obvious were the farmers who were delighted to have been assured of uninterrupted supply of irrigation water and the local politicians who got the credit.

With the diversion excessive quantities of water, electricity generation dropped and the resulting shortfall of power had to be supplemented with increased power purchases from the private power generating companies.

The continuous wastage of water led to the belief that Victoria Stage II was impractical due to insufficient water. It is the private power-generating barons who benefitted from the waste of power-generating water. The CEB staff that was responsible for wastage of Mahaveli waters would have been amply compensated from the private power-generating companies.

(The writer is a Chartered Civil Engineer who graduated from Peradeniya University and has been employed in Sri Lanka and abroad. He was General Manager of State Engineering Corporation of Sri Lanka and left the position in February 2010. He is presently employed at a Chinese construction organisation. He also ran a manufacturing and a sales organisation for over a decade.)