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by M S M De Silva, Chartered Civil Engineer

In the Uva Wellassa, on the eastern side of the Walawe Ganga, lies an enormous extent of arable lands that could be utilized for the irrigated cultivation of rice and other crops. Unfortunately, this region has a very dry climate and neglible water resources. The rainfall is marginal when compared to the neighbouring wet zone regions. The Uva Wellassa does not get the benefit of the heavy rains of the south-west or the north-east monsoons. Also there is hardly any potential ground water resources.

The already developed lands in the Uva Wellassa under the command of the Udawalawe and Lunugamwehera irrigation and settlement projects are currently experiencing severe irrigation water shortages. At the Udawalawe project with a potential irrigable command of 60,000 acres, the left bank canal construction had to be abandoned halfway at Suriyawewa due to a shortage of irrigation water and 20,000 acres of land under its command remain undeveloped. At the Laungamwehera project, with a potential irrigable command of 40,000 acres, water from the reservoir cannot be led into the already constructed right bank canal system to irrigate 20,000 acres of new lands under its command because the water in the reservoir is only sufficient to irrigate the lands under the command of the right bank canal and the Ellagala anicut system.

It has to be recorded that in both the above irrigation and settlement projects, the resident paddy famer uses 20 acre feet of water to cultivate two crops of paddy annually on one acre of land. This high rate of water use is for a specific purpose as a non - toxic weedicide, which is a cultural practice over the ages when water was abundant and also because imported weedicides are uneconomical in view of their high cost.

It therefore becomes necessary to augment the water resources of the Uva Wellassa by the diversion of water from the neighbouring wet zone river basins. Three such sources are available and are described briefly below:

Kukule Ganga

The Kukule Ganga is a major mid-basin tributary of the Kalu Ganga in the western providence. The Kukule Ganga receives the full blast of the south - west monsoonal rains. Most of the annual rainfall comes down in the six monsoonal months April to September each year. The heavy rainfall produces large and repeated flows during the rainy season and during the balance six months of the year, when there is little rainfall, the flow is sharply reduced to an insignificant dry weather flow. At the project site, the Kukule Ganga has a basin area of 120 square miles, an annual average rainfall of 150 inches and annual water yield of 735,000 acre feet which is almost equal to the water yield of the Gal Oya at the Senanayake Samudhra. The Kukule Ganga is a very favourable water resource for diversion to the Uva Wellassa for irrigated agriculture. It has a very large water yield at the project site and is situated only 20 miles away from the Uva Wellassa. Unfortunately, the Ceylon Electricity Board is currently constructing a hydro-electric project on the Kukule Ganga at the project site. Due to the monsoonal nature of the Kukule Ganga, a large storage reservoir is required at the project site for the regulation of its water flows. The construction of a storage reservoir at the project site was rejected due to high displacement of people and livestock, large inundation of cultivated lands and consequent damage to the environment and ecology of the neighbouring Sinharaja rainforest and wildlife reserve. So, instead a diversion weir is to be constructed at the project site, making it the Kukule Ganga run-off-river project.

The entire run-off-river Kukule hydro project will incorporate a 110 meters long and 16 meters high concrete diversion weir with four spillway gates constructed across the Kukule Ganga, an intake structure and sand trap, (on the left bank) a headrace tunnel 5.65km in length with an internal diameter of 6.4 meters (unlined), a 140 meters high vertical pressure shaft with an upstream surge tank, a tailrace tunnel 1.6 km in length and other appurtenances. The power cavern 200 meters underground is to have two Francis units of 35 MW to generate 317 million Kwh of electricity annually with 12.4 hours average daily operatingtime. The regulating head pond capacity will be 1.63 million cubic meters.

The Kukule run-off-river project is not multi-purpose undertaking and therefore it is a wasteful use of scarce water resources. The tail water from the Kukule underground hydro-power station amounting to about 670,000 acre feet annually, cannot be used for the second time, because water is not required for the irrigation of paddy lands lower down on the Kalu Ganga basin. The incident rainfall in that regoin is more than adequate for this purpse. And so, 670,000 acre feet of precious water is wasted to the Indian ocean annually.

This unconcernedly is allowed to take place while simultaneously, only 20 miles east of the Kukule Ganga basin lies the Uva Wellassa undeveloped with over 100,000 acres of arable lands uncultivated and unproductive due to a severe shortage of irrigation water.

The Uma Oya is a major mid-basin tributary of the Mahaweli Ganga. Water can be diverted to the Uva Wellassa from the upper watershed of the Uma oya by the implementation of a reservoir on it, and a tunnel conveyance system to lead the water to a hydro-power station on the right bank of the Kirindi Oya about eight miles north of Wellawaya town. The tailrace water from this hydro-power station will flow along the Kirindi Oya past Wellawaya and Tanamalwila towns and reach Lunugamwehera reservoir in the Uva Wellassa.

However, this water amounting to about 220,000 acre feet per annum can be usurped by the resident farmers with paddy lands on both banks of the river below Wellawaya town for a Yala crop of paddy which they are presently unable to do due to a severe shortage of irrigation water. It is unlikely that a substantial quantity of Uma Oya water would reach Lunugamwehera reservoir in the Uva Wellassa.

Ratnapura town is at the center of the upper watershed of the Kalu ganga. Several tributaries of the Kalu Ganga flowing from the north have a confluence about 5 miles north of Ratnapura town to from the main Kaluganga stream. The other large up-basin tributaries of the Kalu Ganga, namely the Denawak Ganga, the Wey Ganga, the Niniella ganga and Hanguru Ganga confluence with the Kalu Ganga close to Ratnapura town.

The catchments of these tributaries have heavy rainfall and have a large water yield.

Currently, there is a shortage of electricity in Sri Lanka and its demand is increasing by 8 to 10 percent annually. The situation would ease only by the year 2007 when the coal fired thermo-electric power stations are in place. The Kukule Ganga run-off-rover hydro-project will be commissioned in the year 2002 but the generation of electricity at its hydro-power station cannot be curtailed till the year 2007.

In the event the Kukule Ganga waters are diverted to the Uva Wellassa for irrigated agriculture, it is necessary to ascertain whether the income derived from irrigated agriculture there is comparable with the income derived at the Kukule Ganga run-off-river hydro-project.

With the use of about 670,000 acre feet of Kukule Ganga water the Kukule gange run-off-river project can generate 317 million Kwh of electric energy.

The current selling price of one Kwh (unit) of electricity for domestic use is Rs. 5.32 per unit including the surcharge. At a selling price of Sri Lanka rupees 5/00 per Kwh, the total annual revenue amounts to Rs. 1585 million.

Agriculture at Uva Wellassa

With the use of about 670,000 acre feet of Kukule Ganga water, 26,800 hectares of land can be cultivated with one crop of paddy per annum. This amounts to a water usage rate of 25 acres feet per hectare per one crop of paddy annually which is the current water usage rate at the Udawalawe and Lunugamwehera irrigation and settlement projects.

The current average production of paddy in Sri Lanka is 74 bushels per hectare. At 20 bushels to a ton this amounts to 3.7 tons of paddy per hectare. At a paddy/rice conversion ration of 0.64, the equivalent production of rice in Sri Lanka is 2.368 tons/hectare. So total production of rice by one crop on 26,800 hectares of land 26,800 x 2.368 = 63462 metric tons.

Assuming the price of imported rice = Rs. 25,000 per metric ton.

Total revenue from rice production amounts Rs. 1587 million.

It has to be noted that the income in either of the above two cases is almost the same. More important, the revenue obtained from the sale of electricity comes in Sri Lanka rupees and cannot be used to settle the foreign commitments of the Ceylon Electricity Board. On the other hand, the revenue derived from the production of rice in the Uva Wellassa saves foreign currency as this additional quantity of rice can be reduced from the normal import quota of rice to Sri Lanka. These foreign exchange savings could then be used to settle the foreign commitments that the Ceylon Electricity Board had incurred to construct the Kukule run-off-river project. So, the diversion of the Kukule ganga water to the Uva Wellassa for the irrigated cultivation of rice crops appears to be as economically viable as using the same water at the Kukule ganga run-off-rive project for the production of electricity. As mentioned earlier, the only constraint is that the Kukule waters could be redirected to the Uva Wellassa only after the year 2007. Unlike the original idea of constructing a 100 meters high dam and reservoir on the Kukule ganga at the project site that was rejected, these three reservoirs in the upper watershed of the Kukule ganga are located in isolated and uninhabited regions and therefore there is no displacement of people and livestock nor the inundation of cultivated lands.

The engineering community of Sri Lanka is amending their hydraulic project proposals for the Kukule ganga, at the expense of more economically favourable proposals in order to safeguard the environment and ecology of the immensely valuable Sinharaja rain forest and wildlife reserve, which is in extent 19,000 acres or 30 square miles.

Today, there is a new ominous treat to the Sinharaja rain forest reserve. The World Bank, supported by Conservation International (USA) and Global Environment Facility (USA) has come out with an ambitious plan which proposes recovering monies lent by the World Bank to Sri Lanka, which monies remain yet unpaid. The plan comes in the form of swapping the debt owed by Sri Lanka to the USA in exchange for a 30 year lease of the virgin Sinharaja rain forest and wild life reserve.

The above threat looms larger in view of the PA government agreeing to "Consider" the situation with little hope of ever moving out of its debt position and in view of the financial crisis faced by the PA government and the loans awaiting to be obtained from the World Bank at present, it would be difficult, even with the interests of the country at heart, for the PA to reject the offer in its totally. Conservation International does not hide the room plan allows for these investors to carry out research under "conservation", when it speaks of General Environment Facility resource base holding a scientific community. It speaks also of making "best use of resources and expertise" in meeting the "urgent" need of the threat to ecological balance. It will only leave countries like Sri Lanka with greatly exploited forest cover.

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