The Uma Oya project, conceived as an important segment of the Accelerated Mahaweli Programme (AMP), was studied for the development of water resources for hydropower development by the United States Operations Mission (USOM) and the Canadian Hunting Survey Corporation (CHSC) as far back as 1959. Subsequently, the UNDP/FAO Master Plan (1968-1969) for the AMP proposed the construction of the Upper and Lower Uma Oya reservoirs for such purpose.
Lahmeyer International Company in Germany during 1988 -1989 formulated a ‘Master Plan for Electricity Supply in Sri Lanka’ and under this plan identified a three-stage development in Uma Oya for hydropower generation. After the review of the three-stage development by experts from Germany in 1989, a two-stage development was recommended.
The AMP was launched by the Government of Sri Lanka (GoSL) in 1978, which included both the development of water resources and hydropower, with a view to increase the production of food and power generation and to alleviate unemployment. However, the AMP did not cover the development of the Hambantota, Monaragala and Ampara Districts, which have large extents of suitable land for cultivation, where the major constraint is lack of water.
Accordingly, the need to augment the water resources of the above areas based on a policy for irrigated agriculture became a priority and identified the trans-basin diversion of water from the upper catchment of the Uma Oya into the Kirindi Oya as an option.
In view of the above policy decision, a pre-feasibility study of the Uma Oya Multipurpose Trans-Basin Project was carried out by the Central Engineering Consultancy Bureau (CECB) in 1991. It must be stressed that the CECB conceived this project as presently being implemented as an alternative to the in basin hydropower project under the AMP.
The latest study of the Uma Oya basin is the trans-basin concept prepared by SNC Lavalin Inc (Canada) (SNC-LAVALIN) in 2000 in collaboration with the CECB.
As a field geologist who traversed on foot most of the area covered by the Uma Oya basin during the basic geological survey for the preparation of geological maps, I would like to analyse the changes in ground conditions that have given rise to serious irreversible technical and environmental issues that have arisen since the project was launched by the previous government in April 2008.
Geographical location of the project
Uma Oya is a major tributary of Mahaweli Ganga, which has its headwaters in the Pidurutalagala range, Nuwara Eliya, flows through Welimada and Kandeketiya in the Badulla District and the confluence with the Mahaweli River is just above the Rantabe reservoir (Uma Oya falls). The basin covers a drainage area of 700 square kilometres.
Geology of project area
The project area falls within the Nuwara Eliya, Haputale, Buttala and Hanguranketa Geological sheets of 1:50,000 scale (revised from 1:63,360 scale) mapped by the geologists of the Geological Survey Department (present GSMB) form 1965 to 1980 and these maps were available to the teams that carried out the feasibility studies.
The regional geology consists of high grade metamorphic rocks (rock changed by excessive temperature and pressure from sediments over 3000 million years BP) and consists of charnockites khondalites, crystalline limestones, quartzites, etc.
The significant variation of the structural geology of the area in the regional strike, which is mostly east-west with varying degrees and in the lowlands tends to be north-south. The explanation to this change is that the rocks of the highland area (Highland Series) are formed by upliftment of the central plateau millions of years back.
However, another school of thought postulates that this change of elevation was due to erosion. The Subsequent gravity survey carried out by the Geological Survey in collaboration with the New Zealand Geological Survey in 1974 has favoured a theory of upliftment.
The structural geology of the area south of Wellawaya where the trans-basin channel will run to feed the Kirindi Oya will traverse an area with a strike direction of rocks running north south underlain by different rocks such as gneisses and quartzites, etc., grouped under the Vijayan Series.
It is queried whether the experts who carried out the feasibility studies from the CECB as well as the Canadian consultants from SNC–LAVALIN as well as the CEB studied these geological maps and also carried out detailed geological mapping of the area including the proposed reservoir beds, dam sites tunnel traces before construction commenced in 2010.
According to the information collected from the print media, in summary the project envisages the construction of two 30-meter and a 40-meter high dams across the Dalgolla Oya and the Mahatotila Oya (two main tributaries of the Uma Oya at Puhulpola and Dyraaba - close to Atampitiya and Welimada). A link tunnel 4 kilometres long between the reservoirs will also be constructed.
From Dyraaba near Welimada a 3.29-meter wide and a 24-kilometer long trans basin tunnel will be constructed to an underground power station at Randeniya close to Wellawaya on the right bank of Kirindi Oya.
It is envisaged that the installed capacity of the power house at Randeniya will be 90 MW to produce 312 GWh of electricity (recent figure is 231 GWh).
It is proposed to divert 192 MCM of water annually to the Kirindi Oya to augment the Handapangala and Lunugamwehera and Weheragala reservoirs by feeder channels in the lowlands. The recent figures give the flow as 145 MCM, a reduction of over 47 MCM.
The total project cost in the year 2000 was Rs.16000 million (Rs.16 billion) and is funded by the Government of Iran. The recent figures are US $ 450 million (Rs.58.5 billion Sunday Times February 15, 2015) with a project escalation of Rs.42.5 billion.
EIA and environment clearance
The initial Environment Impact Assessment (EIA) of the Mahaweli Project was carried out by Tippets-Abbot-Mc Cathy Stanton (TAMS) of the US and a report was submitted to the then Director General of the Mahaweli Authority in February 1980. At this stage, the project was to be only a hydropower project and not planned to divert water from the upper reaches of the Uma Oya to Kirindi Oya. The 322-page report covered in detail the environment impacts and included land use, soils, forestry, wildlife, fisheries, wetlands and public health and was a valuable guideline for project proponents of the AMP.
An interesting research paper by Dr. Zanar Tokmechi of the Islamic Azad University Mahabad titled ‘Land Slide: A Key Problem in Uma Oya Project Risk Controlling’ published in World Applied Science Journal 12 (9) 1512 -1516 in 2011 had identified risky landslide zones and recommended the “best possible places to arrange buildings and equipment found in the Uma Oya project.” It had been identified that:
“If there is a wrong mobilization the landslide risk will be high.”
“It is clear from results that high risky landslide zones for the Uma Oya project is about 30 percent while, low and no risky zones are about 50 percent and 20 percent, respectively.”
“According to findings we say that it is dangerous to mobilize Uma Oya Project in zones 1, 3, 4 and 6.”
Please note that maps of the six zones are given in the research paper and prudent to check whether these high risk zones were avoided.
The author also stated, “Landslides are aggravated by human activities. Activities include deforestation, cultivation and construction. Main causes can be vibrations from machinery, blasting, earthwork which alter the shape of a slope, removal of deep-rooted vegetation and construction.”
Another research paper by Dr. Zaniar Tokmechi of the Department of Civil Engineering of Islamic Azad University, Mahabad, Iran titled ‘Finding Risky Environmental Zones Due To Flooding In the Uma Oya Project’ published in Advances in Environmental Biology 5(9):2950-2955 in 2011, flood risk zones were identified in the project area and concluded that:
“If there is a wrong mobilization the flood risk is high.”
“It is clear from the results that the high risky flooding zones in the Uma Oya project is 25 percent while low and low and no risky zones are about 50 percent and 25 percent, respectively.”
“According to findings we can say that it is dangerous to mobilize Uma Oya project in zones 2, 4 and 5.”
It is interesting to note that both researchers had identified the entire Uma Oya Project into 14 zones from the hill country to the plains and zones 1, 3, 4 and 6 are subject to landslides and 2, 4 and 5, respectively are subject to flooding with zone 4 subject to both landslides and flooding.
The important issue that has emerged is whether the consultants and the present contractors have avoided these high risk zones or whether remedial measures were taken to avoid them before construction started.
(Dulip Jayawardena, a retired United Nations ESCAP Economic Affairs Officer, can be contacted at email@example.com)