DESALINATION - OR A RIVER FOR JAFFNA?



article_image

Restored Thondamannar Barrage – Part of the River for Jaffna

A River for Jaffna Project Area

Restored Ariyalai Barrage – Part of the River for Jaffna

by Thiru Arumugam


 


Proposed Desalination Plant in Jaffna


 


In 2010 the Asian Development Bank (ADB) approved a total loan facility of 130 million US dollars for the "Jaffna and Kilinochchi Water Supply and Sanitation Project". The local costs of 26 million dollars were to be met by the Government of Sri Lanka. The project involved providing safe drinking water for 300,000 people in Jaffna Town and surrounding areas and sanitation facilities for 80,000 people in Jaffna Town. The source of raw water was to be Iranamadu Tank in Kilinochchi. Water was to be pumped from here to a treatment plant near Pallai in the Jaffna Peninsula, and treated water distributed to consumers from there.


From the outset there were protests from the farmers of Kilinochchi who said that there was presently only enough water in Iranamadu Tank, in an average rainfall year, to cultivate only 30% of the paddy fields for the Yala crop and if water is pumped to Jaffna, then there would be no water left for any Yala cultivation.


In view of these protests, it would now appear that Iranamadu Tank as a source of raw water has been abandoned and the source of water is to be a Reverse Osmosis Desalination Plant sited in the Jaffna Peninsula sea coast at Thalaiyadi, near Maruthankerny, with a capacity of 24 million litres per day (Mld). The original loans appear to have been reduced to 94 million dollars in view of the cancellation of the need for pumping water from Iranamadu to Jaffna and the sewage treatment plant for Jaffna Town has been dropped.


However, Desalination Plants are very expensive to build and run and additional loan facilities amounting to 120 million dollars have been earmarked by the ADB to meet the cost of this plant, making the total loan facilities for this project 214 million dollars plus local costs to be met by the Government of Sri Lanka. Tenders closing on 02 May 2017 have been invited from Contractors to Design, Build and Operate (DBO) a 24 Mld Sea Water Reverse Osmosis (SWRO) Desalination Plant at Thalaiyadi in Jaffna Peninsula.


Desalination Plants are expensive to build mainly because of the high cost of the membranes that are used. Powerful high pressure pumps are also required to pump the water through these membranes and they consume a lot of electricity. A 24 Mld Desalination Plant will probably consume about five to six megawatts of electrical power.


A ball park idea of the cost of desalinated water can be obtained by comparing it with the 100 Mld Minjur Desalination Plant near Chennai, South India where bulk electricity charges are about the same order as in Sri Lanka. The plant was commissioned in 2010 and is operated by Chennai Water Desalination Ltd (CWDL) who sell the treated water to the Chennai Water Supply and Sewerage Board. The contracted selling price of the water negotiated in 2005 is 1.03 US dollars per kilolitre.


Water produced by the proposed Thalaiyadi Plant will be more expensive than this, firstly because the above-mentioned price was negotiated in 2005 and secondly because the Thalaiyadi Plant capacity at 24 Mld is about a quarter of the size of the Minjur Plant and therefore the cost per kilolitre would be higher. A not unreasonable assumption would be that the water produced at Thalaiyadi will cost about 1.20 dollars per kilolitre or 180 Sri Lankan Rupees at current rates of exchange.


The 2013 Annual Report of the National Water Supply and Drainage Board (NWSDB), the latest to be posted on-line, states that the average cost of water production for all their plants is 28 Rupees per kilolitre. In other words, the cost of water produced by the proposed Thalaiyadi Plant will be more than six times the average cost of water produced by all the other NWSDB plants, and will have to be sold to consumers at a fraction of the cost price, thus incurring substantial losses to the Board.


There is however a cheaper alternative source of raw water called "A River for Jaffna Project". This is a scheme designed by local engineers and the capital cost is less than one-tenth the capital cost of a Desalination Plant. Running costs are negligible because there is no pumping involved.


 


A River for Jaffna


The River for Jaffna (RFJ) Scheme was proposed over 50 years ago. Work was started on the scheme at that time and it was partially completed. It is a scheme to improve the fresh water availability in the Jaffna Peninsula underground aquifer, thereby reducing salinity in the Jaffna wells and also make cultivable thousands of acres of land previously uncultivable due to soil salinity. It will also improve the water quality in 30% of the wells in Jaffna which are presently saline, thus making additional water available for agricultural pumping. It consists of the following parts:


(a) Reconstruction of the Thondamannar Barrage to prevent salt water access inland, thereby making Vadamarachchi Lagoon (VL) a fresh water lagoon.


(b) Constructing a new barrage at Ariyalai to prevent salt water access inland, thereby making Upparu Lagoon (UL) a fresh water lagoon.


(c) Blocking the openings under the Elephant Pass road and rail bridges and constructing a new dam and spillway at Chundikulam at the eastern end of Elephant Pass Lagoon (EPL), to make EPL a fresh water lagoon.


(d) Constructing new 4 km long Mulliyan Link Channel to convey water from EPL to VL and UL. Controlled discharge would be made from EPL to VL as the water level in VL dropped due to percolation into the aquifer and evaporation.


All water flows in the RFJ are gravity flows and there is no pumping involved. Items (a), (b) and (c) above were completed about fifty years ago, thus making EPL, VL and UL fresh water lagoons. However due to lack of funds, Item (d), the Mulliyan Link Channel was never completed. Thus water from EPL was never conveyed to VL. After a few years the Chundikulam Dam in EPL breached due to heavy floods. Also the wooden stop logs in the Thondamannar and Ariyalai Barrages perished and all three lagoons reverted to their former condition of salt water lagoons after a few years.


In subsequent years the Irrigation Department tried repeatedly to obtain funds to complete the RFJ scheme but was never successful in obtaining the funds to carry out the necessary repairs and complete the scheme. However, about five or six years ago funds were released for the restoration of Thondamannar Barrage and subsequently for restoring Ariyalai Barrage. This release of funds was consequent to the passing of unanimous resolutions by the Institution of Engineers, Sri Lanka and Pugwash Sri Lanka calling on the Government to complete the scheme. The work on the two Barrages was successfully completed and Vadamarachchi and Upparu are fresh water lagoons once again. Elephant Pass Lagoon, however, remains a salt water lagoon.


The present position is that the Australian Consulting Engineers, SMEC, were asked to produce a National Water Use Master Plan of 30 water projects all over the country. These projects are to be implemented over the next twenty years. A Project Review Committee then studied SMEC’s reports on the 30 projects and rated River for Jaffna as the No. 1 priority project. SMEC were then asked to prepare the Terms of Reference for a Feasibility Study for River for Jaffna, which they have completed. SMEC have estimated that the cost of completing RFJ is Rs 1,412 million or 9.4 million US dollars at current rates of exchange.


ADB’s Final Report on the Jaffna Kilinochchi Water Supply Scheme, Executive Summary, dated March 2006, quotes in Table 10 that the available recommended abstraction rate from the Jaffna aquifer is 25 Mld, which is more than the 24 Mld capacity of the proposed Thalaiyadi Desalination Plant. However, the ADB Report disregards the Jaffna aquifer as a source of raw water as it states that it will require a minimum of 103 borehole/well pumps (page 6). It must be noted that this estimate of 25 Mld was before Vadamarachchi and Upparu were converted into freshwater lagoons, and this together with the similar conversion of Elephant Pass lagoon will increase the water available extraction even further. Borehole/well pumps are appropriate for deep water sources, whereas in Jaffna where the fresh water lens in the aquifer is shallow, the appropriate method would be to use collector wells, because if borehole wells are drilled deep they will tap saline water. Collector wells are large diameter wells about five metres in diameter and the depth of the well should not go into the saline water layer which is below the fresh water lens. From the bottom of the well horizontal adits or tunnels of large diameter are drilled radiating like spokes from the well. These adits act as collectors and increase the available water for extraction several fold over a conventional well. A Sri Lankan Company, Mini-Well Systems has perfected this method and has constructed collector wells with capacities of over 2 Mld each in Biyagama, Horana, Kosgama etc and proposed a scheme for Kattankudy with a yield of 10 Mld. These include collector wells for the NWS&DB. Further details can be seen in the book by V Tharumaratnam and D V Canyon, Sustainable Water from Collector Well Systems in Sri Lanka, Pingelly, West Australia, 2008. Therefore it can be seen that strategically located collector wells in the Jaffna Peninsula can provide the raw water requirements of the Jaffna Water Supply Scheme without having a very expensive Desalination Plant.


In 2009, the writer corresponded with ADB Manila and suggested completing the River for Jaffna Project and drawing water from the Jaffna aquifer as source of water for the Jaffna Water Supply Scheme. Alternatively, Elephant Pass Lagoon could be considered as the raw water source after conversion to a fresh water lagoon. A reply was received dated 20 July 2009, signed by the Director, Urban Development Division, South Asia Department, ADB stating inter alia that "We agree with you that the proposed River for Jaffna would provide benefits primarily for agriculture and ground water recharge........... The River for Jaffna should be further considered.......".


The irony of the situation is that if the Thalaiyadi Desalination Plant is completed and the River for Jaffna is not, for several months of the year there will be fresh water from Kanaganarayan Aru flowing into Elephant Pass Lagoon and gushing out to the sea at Chundikulam and diluting the sea water over a large area. Meanwhile about a couple of kilometres to the north at Thalaiyadi there will be a Desalination Plant labouring and expensively converting the diluted sea water back to fresh water !!!


The Northern Provincial Council is holding a Northern Province Water Resources Development Colloquium in Jaffna from 28th to 30th January 2017 and it is hoped that this matter will be considered in depth at the Colloquium.


 
 
 
 
 
 
 
 
 
 
animated gif
Processing Request
Please Wait...