Uma Oya Trans-Basin Multipurpose Project – A critical review

9 April 2015 07:11 am - 1     - {{hitsCtrl.values.hits}}


Economic feasibility of Uma Oya Project

In an article published in Sunday Island of April 25, 2008, Dr. G.T. Dharmasena, former Director General of Irrigation and a consultant to United Nations Project Services in Sri Lanka (UNOPS) stated, “It has to be noted that it is not logical to assume that all available water at the dam sites can be diverted due to downstream water requirements and also to the rapid fluctuations of water levels in the river caused by flash floods.
From detailed studies it was found that from the annual total of 211 MCM of water volume, only 130 MCM can be diverted to Kirindi Oya based on the most recent estimates of 211 MCM of total water. Based on this, the annual generation of power estimated at 175 GWh. This is a reduction of 56 percent in comparison to the estimate of 312 GWh made by consultants LAVLIN.”
Dr. Dharmasena also stated: “In view of the above, it is expected from the officials engaged in the planning of the first layout of the project to take the following matters into consideration during the initial stage of the implementation of this project.”
n“The water availability in Uma Oya has to be refined by an intensive hydrological study using the current techniques and most recent hydrological and land use data.”
  • “Downstream irrigation and water supply requirements within Uma Oya below dam sites should be thoroughly assessed.”
  • “Environmental and social implications due to diminished flow in Uma Oya and acceptable minimum flow have to be established.”
  • “The impact of Mahaweli System C (Aranaganwila) and B (Maduru Oya) as a result of the diversion has to be considered.”
  • “Based on a critical review of water availability in Uma Oya for trans-basin diversion, it is appropriate to review the economic viability of the project once again.”
It is queried whether the above issues were appropriately dealt by the project proponents and the consultants, including the Central Engineering Consultancy Bureau (CECB) before the commencement of project activities.
Dr. Dharmasena also gave an alternate suggestion to provide water for the Moneragala, Hambantota and Ampara Districts, which is as follows:
  • “The Kumbukkan Oya is a major river in the Monaragala District discharging about 470 MCM of water annually to the sea. There is no possibility of utilizing this water within Kumbukkan Oya due to the geographical location of the Yala National Park. Most of the irrigable lands lie within the sanctuary and therefore this water has to be diverted to another basin for development. One of the most attractive diversion proposals is to divert this water by damming Kumbukkan Oya at a suitable location to Veheragala reservoir in the Menik Ganga basin via a trans-basin reservoir. Then this water can be diverted from the Veragala reservoir to Lunugamvehera via the existing system.”
It is queried as to why the CECB and Canadian consultants LAVLIN did not look into this alternative proposal without giving preference to the Uma Oya project. 
Emeritus Professor C.M. Madduma Bandara of the University of Peradeniya in a lecture delivered recently, under the title ‘Adapting to Climate Change: The Role of Higher Education and Research’ commented on the Uma Oya as a critique below:
  • “Whereas the Government of Sri Lanka (GoSL) promotes the project for its irrigation and power generation benefits, others are more cautious and warn that the Uma Oya Watershed cannot sustain such water diversion. Currently, water from Uma Oya is utilized downstream to irrigate agricultural areas under the Mahaweli Project. With the construction of the Uma Oya Project, yet more water would be diverted from the river.”
  • “With the construction of the reservoirs and the tunnel, people living upstream of the planned tunnel are also likely to suffer from water shortages.”
The writer strongly believes that the above predictions from the learned professor, which are in harmony with the experienced former Director General of the Irrigation Department, have now become a reality and the question remains what possible effective remedial measures are possible to make this project feasible.

Geological factors related to tunnel failure and land subsidence
The tunnel trace as seen from the surface leads to a drastic change in elevation from the intake site at Dayaraba close to Welimada to the underground power station at Randeniya. The area is frequently underlain with limestone subject to rapid weathering. The apparent loss of water from surface wells may be due to a cast topography that led to underground flow of water to the tunnel along these cast zones.
The land subsidence experienced recently near Bandarawela is due to sink holes in a limestone terrain seen by the writer while traversing the hilly terrain. 
It is queried whether the tunnel trace was drilled at regular intervals before tunnel excavation after detailed geological mapping to locate areas overlain by limestone and other  rocks that are easily subject to weathering. The percentage of core recovery will be an indication of such underground cavities.
The writer has been traversing on foot over the surface of some of these areas along the underground tunnel trace and had noticed sink holes especially in the area over Welimada and Bandarawela and the famous Dowa Cave temple could be above the tunnel.
If such unfavourable and weak zones were detected by surface mapping and underground drilling, the tunnel trace could have been changed before construction started.

The water released from the Randeniya power station will be used to supplement Handapangala and Lugamvehera and the Weheragala reservoirs before release to the Kirindi Oya. Such flow of water will be from two main channels that would flow without many problems except for the disturbance of the wildlife in the area. It is believed that the Handapangala is the habitat of dwarf elephants and this rare species will be extinct when the project is completed.

Conclusions and recommendations
Sunday Times on March 29, 2015 under the heading ‘Uma Oya Project sees some light at the end of the tunnel’ reported that expert committees consisting of 120 members from the CEA, NBRO, GSMB and academics from the University of Peradeniya   have submitted reports putting forward solutions to the recent problems encountered by the Uma Oya Project. In addition, the   CEA has also submitted its own report.
The critical issues raised in this article may be helpful to come to a conclusion whether this project should go ahead or not. The main problem that has emerged at present is the flow of water into the tunnel and the drying up of domestic wells and land subsidence upstream especially in the Bandarawela and Welimada areas.
The writer must commend the initial work carried out by the former Director General of the Irrigation Department and research by Emeritus Professor Madumma Bandara, who predicted the present environmental disasters, and it is surprising that these two are not in the committee appointed by the GoSL as their valuable advise will be helpful to take a final decision on this project, which has now reached an advanced stage. According to the paper reports, the construction of the underground tunnel is almost completed.
The writer also appreciates the two Iranian scientists who published research papers on their findings in 2011 on the environmental impact of the Uma Oya Project focusing on landslides and flooding and it should be queried whether serious consideration was given by the CECB and the Iranian project contractor as well as other consultants. 
It is also reported that the underground power plant at Randeniya will be constructed by Poyry Engineers from Vantta, Finland. The writer is not aware whether the construction has commenced and if so, caution must be exercised as there are limestone and quartzite bands in this area.
The writer was involved in resolving the leaking of water from the Ukuwela underground tunnel under the AMP in the late 1970s and it was resolved by injecting a violet dye on the surface and tracing the dye inside the tunnel and sealing the leak. The leak was between two major rock bands.
Another method is to introduce radio isotopes from some of the surface streams and domestic wells if not harmful to health and detecting the isotopes in the water inside the tunnel. It is recommended to get the advice from the Atomic Energy Authority (AEA). This method was proposed to monitor the movement of minerals sands from upstream of the Mahaweli River to Pulmoddai and also on the intake of phosphate by plants in soils mixed with rock phosphate from Eppawela.
In conclusion, a more detailed study should be carried out to come to a definitive conclusion on the economic and environmental feasibility of this mega project without rushing to conclusions with inconclusive technical evidence. It is also commented on the dramatic increase in project costs from Rs.16 billion in 2000 to the present Rs.58 billion after project activities started in 2010. The CECB is the project consultant and is under the Mahaweli Development Ministry. Further, the GSMB and the CEA are also under the same ministry and the question has arisen whether there is a conflict of interest with project proponents and consultants as in the Port City Project commented by the writer some time back.
The reader could also access the writer’s article on landslides falling within the Uma Oya basin published in the Daily Mirror Business section on 5/11/2004.
(Dulip Jayawardena, a retired Economic Affairs Officer United Nations ESCAP and former Director Geological Survey Department – present GSMB from 1983 to 1985, can be contacted at
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  • Lalith Thursday, 16 April 2015 12:29 PM

    FIY and Visualization the Issue ajith

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