Final phase of Mahaweli Development Scheme underway:

Drought emphasises need for urgent completion

by Gamini Warushamana

The final phase of the Mahaweli Development Project (MDP) is now underway to address water shortages in the Dry Zone up to Northern province. The prevailing drought has emphasised the need for urgent completion of the project.

Additional Secretary, Ministry of Irrigation and Water Resource Management (MIWRM), Sisira Kumara told Sunday Observer Business that this project, especially the North Central Province (NCP) canal is the only way to provide water to remote areas of the NCP and North Province (NP) and a long-term and sustainable solution for the issue.

Excerpts of the interview.

There is a misconception that the NCP Canal project is only to provide water to the Iranamadu tank in the North.

Iranamadu tank is the last major reservoir included in the MDP to provide Mahaweli water under the NCP Canal similar to other major reservoirs in the NCP which benefited from the diversion of Mahaweli waters.

In the next 25 years water will become the most important commodity and sharing this equitably while establishing the water rights of the farmers who enjoy such rights at present, will be the only way to take this country to prosperity while improving the living standards of the poor farming community in the area.

There are three major components of this phase; Moragahakanda and Kalu Ganga reservoirs and North Central Province (NCP) Canal. Construction works of the two reservoirs are now under way and are the last two major reservoirs in the Mahaweli Development Project planned in 1968.

The Moragahakanda reservoir is the most important in the Mahaweli system to address irrigation water deficit of developed Mahaweli areas under Polgolla-Amban Ganga complex. The NCP canal will supply water for irrigation to the areas identified in the Mahaweli master plan, further North in the Dry Zone.

The capacity of the Moragahakanda reservoir is 570 million cubic meters (mcm) and the dam is being constructed across Amban Ganga.

The capacity of the Kalu Ganga reservoir is 250 mcm and the dam is being constructed across the Kalu Ganga.

These two reservoirs will add around 820-mcm additional water capacity to the existing Mahaweli system enabling added flexibility of water allocation and will help to reduce the adverse impact of climate change anticipated in the future.

As per the water balance studies there will be an excess of 100 mcm of water which could be transferred from Kalu Ganga reservoir to Moragahakanda to be used in other areas. This excess water in the Kalu Ganga reservoir will be transferred to Moraghakanda reservoir through a nine-kilometre long link tunnel.

The Mahaweli Authority of Sri Lanka (MASL) has planned to provide this water to Manankattiya - Mahakandarwa tanks which are in need of additional water as per the MDP. The total area expected to benefit from Moraghakanda and Kalu Ganga complex is about 93,122 hectares.

Water rights

There is a misunderstanding among some sectors that once the Moragahakanda and Kalu Ganga reservoir project are completed, the people in Polonnaruwa would be deprived of water rights due to the diversion of the Kaluganga and Ambanganga.

This is not true because water available in the two reservoirs with the diversion of the Mahaweli river through Polgolla is not sufficient to provide water beyond Mahakandarawa tank.

In the planning stage of the Kalu Ganga reservoir, the farmers in the Polonnaruwa area specially the farmers under Parakrama Samudra irrigation scheme who receive Kalu Ganga water at present through the Angamedilla diversion scheme protested regarding their water rights.

Accordingly, the Irrigation Department (ID) and Mahaweli Authority of Sri Lanka (MASL) and GA Polonnaruwa on behalf of the farmers signed a memorandum of understating that at times of water shortage, priority will be given to transfer water from either Moragahakanda or Kalu Ganga reservoirs to Parakrama Samudra and ensure their water rights in the future.

The NCP canal sub project is vital to address the plight of the farmers in most remote areas of Kebithigollewa, Horowpothana, Medawachchiya, Kahatagasdigiliya, Rambewa and Mihintale in the NCP including Padaviya - Wahalkada and Pavattakulum schemes.

People in Vavuniya and Killinochchi in the Northern Province (NP) also suffer due to a severe water shortage. Further, an acute kidney disease is fast spreading in the NCP threatening the lives of the people.

The provision of safe drinking water has been identified as one of the measures to combat this disease.

According to areas recognised as Mahaweli areas by the government in 1979 all the people under MDP have an equal right to get their share of water.

The objectives of MDP are to divert the surplus water of Mahaweli river basin for irrigation of 365,000 ha to attain self-sufficiency in food, provision of land and job opportunities to landless people and hydro-power generation. However, by 2012, 44 years after the launch of the project, only 150,000 ha or 41 percent of the work has been completed.

Over time, the government has revised MDP accounting for socio-economic changes and national development priorities.

The government's present priorities for the irrigation and water resources sector focus on ensuring availability of water for irrigation and minimising variations in water availability by implementing trans-basin diversions to divert water to dry zone areas.

In November 2012 Government approved the Upper Elahera Canal from the Moragahakanda reservoir to launch the delayed NCP canal project.

NCP Canal area

As originally proposed in the MDP, Moragahakanda and Kalu Ganga are the main irrigation infrastructure needed for the development of NCP canal project area.

The Ministry of Irrigation and Water Resource Management (MIWRM) carried out a comprehensive water balance study and the study considered present environmental, social and technical constraints.

This study has identified two water sources for optimum use of water in the Mahaweli river and adjacent river basins.

One is the transfer of water from Randenigala reservoir augmented with Heen Ganga and Hasalaka reservoirs. The Heen Ganga and Hasalaka are two major tributaries in the left bank of the Mahaweli river and most of the water presently flows to the sea through Mahaweli river without being used.

Simultaneously it is proposed to divert lower Uma Oya water to Randenigala through Lower Uma Oya reservoir with the development of hydro power to compensate power loss due to transfer from Randenigala. This source will trap the present spillage amounting to about 900 mcm annually of Mahaweli water from the Minipe anicut located below Mahaweli major cascade Victoria, Randenigala and Rantambe.

Diversion

The Minipe anicut is the gravity water diversion point to Minipe scheme (system E) in the Mahaweli left bank and systems C and B under Maduru Oya reservoir in the Mahaweli right bank.

After allowing for environmental releases and the need of water for new development projects, it is proposed to divert about 550 mcm annually from Randenigala using spilling water over Minipe anicut with another 150 mcm from Heen Ganga and Hasalaka reservoirs to Kalu Ganga reservoir and will be used to augment the Moragahakanda reservoir.

This route will add additional effective storage (Victoria and Randenigala) to the Mahaweli system and open another water transfer route to Moragahakanda reservoir adding flexibility to existing water transfer systems in the Mahaweli-Amban Ganga complex to mitigate climate change effects witnessed today and resulting in greater flexibility to the Mahaweli system.

The second source needs, lifting of water from Mahaweli river at Kalinganuwara in the Mahaweli river, considered as another ancient water diversion point combined with Angamedilla in the Amban Ganga. In the original Mahaweli Master Plan lifting of about 800 mcm of water annually amounting to about 30% of water requirement of NCP canal development area is proposed from Angamedilla.

Dry year

Under the proposal, the quantity lift has been reduced to about 300 mcm of water annually to Moragahakanda system.

Even in a very dry year such as 2014 sufficient water is flowing in the Mahaweli river and part of this water if lifted could be used to minimise the drought conditions prevailing in the NCP.

This source also will add great flexibility in the operation of the Mahaweli system facilitating early commencement of cultivation in the Mahaweli system 'G' area and other existing major irrigation systems and will pave the way for optimum use of Maha rainfall in the NCP.

Supplementing Moragahakanda from the above two sources it is possible to provide approximately 1000 mcm from Moragahakanda to NCP Canal area including 70 mcm is allowed as drinking water. Thus, it should be clearly understood that full development of NCP canal is possible only with transfer of water through the above two sources to Moragahakanda reservoir complex.

Once additional water is transferred then it is possible to extend the NCP Canal beyond Mahakandarawa tank without affecting the Polonnaruwa irrigation system. An environment-friendly water diversion system is proposed from the NCP Canal to feed the minor tank cascade system.

This comprises about 1,000 tanks situated in the ancient settlement areas of which major part lies in NCP, north of Anuradhapura and the balance part in Northern province in an around Vavuniya town, fulfilling the dream of the farmers in the area.

Neither large-scale system development as done in the past nor new areas have been proposed for development. The existing forest areas will be linked to create large forest range areas for co-existence of wildlife minimising the human-elephant comflict in the area.

Another notable achievement in this project is paving the way for diversion of the Mahaweli to water scarce Hakwatuna Oya scheme in the upper Deduru Oya basin and upper Mi Oya irrigation system in the driest areas of the NWP in the Polpitigama, Galgamuwa and Ehetuwewa and Yapahuwa Pradeshiya sabah areas fulfilling the dreams of farmers in the area.

It is estimated that about 130 mcm of water could annually be transferred to this area through the existing Wemedilla-Dewahuwa water diversion system while stabilising the systems further.

Climate change

Today, the country is going through one of the severe droughts in recent times with no rains in some parts of the country for the past nine months.

The only way to fight future climate change effects, drought and floods in the NCP is to add storage capacity to the Mahaweli system. The proposed supplementary water diversions linking the existing and proposed irrigation infrastructure will minimise these effects in the future.