Features

The Salinity Barrier and Nilwala Floods: Clearing up Misconceptions

Published

2 years ago

2024/01/7

Thilina Walpola

Figure 1: Salinity Barrier across Nilwala River

by Dr. R. Galappatti,
Chairman, Lanka Hydraulic Institute (LHI).

Introduction

Recent experience of high water levels in lower reaches of the Nilwala Ganga has been attributed by various parties to the construction of the Salinity Barrier in 2018-2022, 5.4 km upstream of the sea outfall. While it is understandable that the affected communities would blame the most recent construction in the river channel for this, many technically qualified persons have also subscribed to this view without either examining hydraulic computations or making any measurements at the barrier. We are concerned that ill-considered attempts are being made to interfere with the structural integrity of the barrier and endanger a major piece of water supply infrastructure.

The salinity barrier is designed to protect the water supply intakes from salinity intrusion and ensure an uninterrupted supply of drinking water to around 600,000 consumers by the year 2035, in the Matara and Hambantota districts, under the Matara Stage IV Water Supply Project of the National Water Supply & Drainage Board (NWSDB). The conceptual design of the barrier including its dimensions, levels and operating rules was carried out by Lanka Hydraulic Institute (LHI).

Regular review meetings were held at regional level by the NWSDB with participation of the Irrigation Department. The Central Engineering Consultancy Bureau (CECB), the EIA consultant, also participated, with full access to the details of the ongoing work at all stages of the study. Modifications were made to the study approach and the designs as required.

The hydraulic studies including design calculations were carried out and the main parameters of the barrier were determined and verified using physical and numerical model studies. This focused on the salinity barrier, particularly its flood impacts, and led to a positive EIA report after public consultations were completed. Detailed designs and construction of the barrier was carried out by a Korean Company (Kolon Samsung C&T) with Ceywater as the local design partner under a Design-Build contract.

The Salinity Barrier

The final design consists of providing a 5-bay gated type structure with vertical lifting gates and piers across the inner stream section 5.4 km upstream of the sea mouth, in the river reach between Thudawa Pump station and Navimana ferry crossing. The gates are 10m wide and 3.1m high with the gate sill fixed at –2.5 m MSL. Gate top at closed position is at +0.6 m MSL and the gate bottom in fully open position is to be at 5m MSL during high and normal flow conditions. This level is above the High Flood Level, as the top level of the flood bund is only around 4.3 m MSL.

Three of the five gates were to be made of two separate sections to allow the upper section to be lowered independently, to make it possible to lower the upstream pool level when necessary for irrigation water management at the request of the Irrigation Department. Sheet-pile cut-off walls were provided across the low-lying areas of the flood plain on either bank to prevent saline water bypassing the main structure during operation and to ensure that during dry weather the river flow is confined to the inner channel and not to overflow into the floodplain. In addition to these main features, gate operating structures, cut-off walls, access roads etc. were included in the design.

The barrier is in full conformity to the stipulations in the MOU signed between NWSDB and the Irrigation Department in March 2017, and the Irrigation Department granted approval for the NWSDB to implement the project.

Figure 2: Salinity Barrier across Nilwala River

Impacts of the Salinity Barrier

The increase in river water level during floods, and operating conditions and concerns of the stakeholders due the proposed structure, were the main considerations in determining optimal values for gate openings, gate sill levels and other parameters for the design.

The upstream flooding impact of the barrier design was computed using a numerical model and verified by carrying out a series of physical model tests at Lanka Hydraulic Institute (LHI). These were used to verify that the flow pattern around and downstream of the gated structure was satisfactory.

The water levels in the upstream river reach, with and without the barrier, were estimated for different flow conditions including floods up to 100 yr return period. The estimated anticipated water level rise just upstream of the Salinity Barrier was about 1 cm maximum during floods of 100 yr return period. There was a higher (4-7 cm) relative water level rise during bank full and low return period floods.

Backwater propagation lengths have been calculated and these anticipated water level rises were considered acceptable. It is relevant to note that, the acceptable head loss at the planned Kelani Ganga salinity barrier was fixed in the range 5 cm to 6 cm for a 100 yr flood.

As far as the flood impact of the cut-off wall is concerned, the impact will be negligible because this wall, with a top level of only 0.8 m MSL, will be well and truly submerged during a major flood. Further there is an allegation that debris might trap buildup from the river bed level to the sill level of gates, and exacerbate flooding. Even if debris are accumulated, its total hydraulic impact is still negligible. Further, fresh bathymetric survey conducted in Dec 2023 has even revealed that there is in fact no debris accreted upstream of the gate structure.

Long inundation period during present flood compared to previous floods

While it has been demonstrated that construction of the Salinity Barrier is not the cause of recent floods, it is nevertheless necessary to investigate why this long inundation of paddy lands occurred and determine what actions need to be taken to prevent or reduce the probability of a recurrence.

In this context it is necessary to examine what happened in May 2017 when there was an extreme flood event in this basin. The flood was caused by an extreme rainfall event of about three days duration that caused a sharp flood peak reaching a daily average water level of 4.32 m MSL at Thalagahagoda on the very next day. The water levels receded to normal levels within the next ten days while it took seven days to decrease to flood alert level (1.4 m MSL) at Thalagahagoda. The return period of this flood is said to be between 75 and 100 yr.

Figure 4: Rainfall Pattern and Drawdown of Water Levels during 2017 Flood

The duration of the long series of rainfall events that spread out over more than two months from Mid-September to end November 2023 is markedly different – both from the point of view of the basin and the time of the year when it took place. While the water level at Thalagahagoda peaked only at 2.92 m MSL in 2023, the level continued to stay above 1.7 m MSL (Minor flood level) for almost the entire period (Oct to mid of Nov).

Figure 3: Rainfall Pattern and Drawdown of Water Levels during Sep Oct 2023 Flood (06th Sep – 22nd Nov 2023)

The markedly different nature of this flood – including its extremely slow recession could only be explained by considering the retention (storage) of flood water on the flood plain which is divided into two on either side of the Nilwala flood bund. The area adjacent to the river will drain slowly into the river channel in the normal manner. The water collecting in the “protected area” must be pumped out at a few pumping stations located along the flood bund.

Duration of operation of these pumps is on record but their pumping rate is not known. An additional point to be considered is that the measured water level profile on the short river reach downstream of the barrier show a steeper slope indicating a more constricted channel from the railway bridge to the sea.

It is also important to note that the rainfall pattern in 2023 is unusual and unexpected, and that no usual rainfall runoff model could accurately interpret it. The models, in turn, must be more detailed, to include the flood plain storage and pumping rates to represent the flood routing performance of the system under such unusual rainfall patterns which might be a trend caused by climate change.

It must also be borne in mind that the Nilwala basin is not a stranger to flooding, though not so late in the year. The steep upper basin that descends suddenly into a largely flat coastal plain is characteristic of all large wet zone rivers in Sri Lanka.

Conclusions

The long-duration flooding experience in the Nilwala basin in 2023 has not been caused by the construction of the Salinity Barrier.A more detailed representation of the flood plains and pump operation is needed to quantify accurately the long recession of the flood plain

The marked change in rainfall patterns might be due to a climate change effect and this type of effect might also impact other river basins in the wet zone. This requires attention.

The ill- considered removal of the low cut-off wall across the lower floodplain should be restored to avoid possible shut down of water supply intakes in the next dry season.

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Features

Proactive peacemaking becomes a paramount need

Published

5 hours ago

2026/06/4

Sahan Weerasooriya

Wasting wars: Some war-displaced people in Lebanon. BBC

It may be some time before the full impact of food inflation is felt in the West. Until such time the world would continue to keep itself in suspense over whether the Trump administration is in earnest when it seeks to convey the impression that it is backing a negotiated solution in West Asia.

As is usually the case, consumer stress would be one of the final determinants of political change. To the degree to which the average US consumer somehow ‘muddles through’ and puts the food on the table, to the same extent would the Republican sections of the US public in particular be tolerant of the Trump administration’s inconsistent handling of the West Asian war and the main issues stemming from it. That is, there would be no grave popular disaffection and a demand for political change in the short term.

However, the indications are that the Trump administration’s support base is suffering some erosion in the wake of the current economic crisis. While reports indicate that Democratic sections are firming-up their opposition to the political centre, Republican support for Trump is also showing signs of waning, we are given to understand.

The above developments are probably why Trump is on record as having given Israeli Prime Minister Benjamin Netanyahu a ‘dressing down’ recently on his seeming intransigence on the question of giving negotiations a chance in West Asia. The show of displeasure could be really aimed by Trump at containing the impatience of the American public.

However, the current ground situation in the Middle East, particularly the uncontained bloodshed, is likely to impress on the thinking sections of the world that more than temporary political change is needed in West Asia and the US.

A well thought out political solution that addresses all the contentious issues at the heart of the Middle East conflict is what enlightened opinion would demand, and very rightly. Right now, the ‘peace efforts’ initiated by the Trump administration give the impression of being piecemeal solutions at best.

There have been, of course, numerous initiatives in the past aimed at bringing permanent peace to the Middle East. These failed mainly because they did not address in full the root causes of the conflict.

At bottom the Middle East conflict is mainly about race and religious hate bred by socio-economic and material inequalities. For instance, if the Palestinian people were not displaced and deprived of land occupied by them at the time of the founding of the Israeli state, ethnic enmities would not have grown to the current unmanageable proportions.

When addressing the above questions, though, it must be remembered that the Israelis too were a displaced people who were entitled to land and a state of their own in the Middle East. Basically, out of these seemingly irreconcilable and conflicting demands have grown the Middle East imbroglio.

Middle East peace is considerably about reconciling these demands and arriving at a solution that would ensure the creation of two states that would opt for peaceful co-existence thereafter.

As long as the US does not see the need for a non-partisan solution that addresses the needs of both ethnicities and religions and goes all-out, as it were, to have it implemented, the Middle East would continue to bleed.

However, staunching the blood flow through the creation of two states would be only half the job done, though a very important part of it. More pernicious, pervasive and difficult to remedy are the inter-ethnic and inter-religious hatreds that have been unleashed over the decades.

However, if substantial, long-lasting peace is to be fostered in the region the latter ‘demons’ would need to be exorcised from the hearts and minds of the communities concerned. No doubt an uphill task but one that must be undertaken by those who wish the region well.

The UN would need to put its ‘best foot forward’ in such undertakings but it is time that it dawned on the international community and other caring quarters that Middle East peace, and all other such uphill challenges, require proactive peacemaking on the part of all civilized sections for their effective management. That is, public involvement in peacemaking too is a must.

Since hatreds are harboured in the human consciousness the enmities embedded in the latter need to be managed and defused judiciously alongside other undertakings in a peace process. In the case of West Asia, such enmities could be even spread globe-wide besides being multi-dimensional. For instance, it ought to be thought-provoking that Iran is insistent on a peace initiative that would also include Lebanon.

Besides security considerations it is also ethnic and religious affiliations that account for Iran making this demand. For instance, the Shias are a numerically important religious community in Lebanon and they provide a significant number of Hizbollah fighters, who are in a vital sense carrying out a ‘proxy war’ for Iran. It also needs to be factored in that Iran is a Shia-majority country.

Thus trans-border religious affiliations could add to the complexities and enormity of ethno-religious conflicts. However, the task of managing centuries-long enmities needs to be launched and prodded on with by peacemakers since a downing of arms alone would not guarantee substantive peace.

It is not realized sufficiently that the process of ending hatreds begins with mutual apologies by antagonists to a conflict for the harm inflicted on each other. This would be anathema in some ears but there is no getting away from the requirement. It is the vital first step to permanent peace anywhere.

In fact there could be no reconciliation worth speaking of without such mutual apologies. It is a point worth re-iterating in these times when even the government of Sri Lanka is voicing the need for national reconciliation. Well, without the words, ‘I am sorry’, there could be no permanent end to enmities – they would do well to remember.

The above requirements may not go down very well with governments, but they resonate in the hearts and minds of most people, since they are inheritors of religious traditions of some kind.

This is a principal reason why peacemaking works well when publics too are involved in them. The effectiveness of such campaigns increases several fold when they have a Mahatma Gandhi or a Jawaharlal Nehru at their helm. A strong proactive involvement by the public in peace could lead to the emergence of such leaders at some point in these campaigns.

Features

Dialog Brings Sri Lanka’s Largest Digital Vesak Experience to Matara

Published

5 hours ago

2026/06/4

Sahan Weerasooriya

From left to right: Hon. Saroja Savithri Paulraj, Hon. Sunil Handunnetti, and Lasantha Theverapperuma experience the Dialog 5G Ultra-powered VR tours.

Official Digital Partner of the 2026 ‘Dakshina Prabha’ National Vesak Zone

Dialog Axiata PLC, Sri Lanka’s #1 connectivity provider, collaborated with the Ministry of Buddha Sasana, Religious and Cultural Affairs to bring one of Sri Lanka’s largest and most technologically advanced Vesak experiences to the ‘Dakshina Prabha’ National Vesak Zone. The three-day celebration, in Matara attracted more than hundred thousand visitors, who engaged with a series of innovative digital activities powered by Dialog 5G Ultra, including Artificial Intelligence (AI) and Virtual Reality (VR) experiences, digital pandols and a Data Dansala. The opening ceremony was attended by Hon. Sunil Handunnetti, Minister of Industry and Entrepreneurship Development and Hon. Saroja Savithri Paulraj, Minister of Women and Child Affairs, along with distinguished guests and Dialog’s senior management.

One of the key attractions at the venue was the Dialog 5G Ultra-powered Virtual Reality (VR) experience, which attracted more than 35,000 participants. The activation enabled devotees to virtually visit and pay homage to sacred Buddhist sites, including the Jaya Sri Maha Bodhi in India and the Atamasthana in Anuradhapura, directly from the Vesak zone in Matara.

Visitors receive complimentary mobile data through Dialog’s QR-powered Data Dansala.

Dialog also conducted an AI Digital Vesak Greeting Card Competition from 21 May to 01 June 2026, attracting numerous entries from across the country. The shortlisted designs were showcased across 20 large LED screens throughout the venue and across Matara City, and were also made available for download via mobile devices. Further, through the use of AI, traditional Jathaka Katha were reimagined in a digital format, demonstrating how technology can be used to preserve and enhance cultural and religious heritage. Together, these initiatives blended traditional Vesak celebrations with emerging technologies, offering visitors a unique and immersive way to engage with Vesak traditions.

Extending the spirit of Vesak through connectivity, Dialog conducted a special Data Dansala powered by its QR Reload platform, enabling visitors to receive complimentary mobile data by scanning QR codes placed across the venue. In addition to the Matara National Vesak Zone, similar Data Dansala activations were also conducted at the Gangaramaya and Bauddhaloka Vesak zones in Colombo.Visitors also had the opportunity to create personalised Vesak-themed digital photos through an AI Photo Booth, generating AI-enhanced portraits using their own photographs and adding a contemporary digital element to the Vesak celebrations.

Visitors watch AI-generated Jathaka Katha

Commenting on the initiative, Hon. Sunil Handunnetti, Minister of Industry and Entrepreneurship Development, said, “The 2026 Dakshina Prabha Vesak Festival marked the first time AI-powered digital innovations were incorporated into a National Vesak Festival in Sri Lanka. Presenting Buddhist stories and teachings through technology created a new and engaging way for visitors to connect with these traditions. We thank Dialog for supporting this initiative and for working closely with us to bring our vision to life. Their contribution played an important role in making this first-of-its-kind event a reality.”

Lasantha Theverapperuma, Group Chief Marketing Officer of Dialog Axiata PLC said, “We thank the Government of Sri Lanka for the opportunity to support the 2026 Dakshina Prabha National Vesak Festival and for embracing technology as part of this year’s celebrations. As the Official Digital Partner, we were privileged to contribute through our Dialog 5G Ultra and AI capabilities, creating new ways for visitors to engage with Vesak traditions while preserving their cultural significance for future generations.”

Beyond supporting the National Vesak Zone in Matara, Dialog also enhanced the Gangaramaya and Bauddhaloka Vesak zones through a range of digital activations during the Vesak season. The company additionally continued its sustainability initiatives, including the Thirasara Aloka Poojawa, which illuminated rural places of worship through solar-powered lighting solutions.

Features

Beauty, elegance and talent…for women

Published

5 hours ago

2026/06/4

Sahan Weerasooriya

Universal Woman is an international pageant focused on “beauty, elegance, and talent” for women, positioning itself as a platform to shape global ambassadors. The 2026 edition will be held in Cambodia, and Sri Lanka will be there, as well.

According to reports coming my way, contestants, at the international event, will work with industry trailblazers, under international standards.

Sri Lankan supermodel, runway and pageant trainer Chulpadmendra Kumarapathirana, is the National Director for Universal Woman Sri Lanka 2026.

With over two decades in the industry, Chula was crowned Miss Sri Lanka 2006, and has since shaped the next generation of titleholders through her Colombo-based Chulpadmendra Catwalk Studio, widely regarded as one of the country’s leading modelling academies.

The team behind Universal Woman Sri Lanka 2026

A former host of Derana Miss Sri Lanka for Miss World 2008 and a judge for Miss Universe Sri Lanka 2025, Chula now serves as National Director for Universal Woman Sri Lanka 2026, leading the franchise’s search for Sri Lanka’s delegate to the international final in Cambodia.

Applications for Universal Woman Sri Lanka 2026 are being taken, via WhatsApp: 077 659 4994, says Chula.

The judging panel for Universal Woman Sri Lanka 2026 includes Senaka De Silva, Pageant Aesthetic Advisor & Chairperson of the Judging Panel, Angela Seneviratne, Caroline Jurie, Rozelle Plunkett, and Suraj Mapa.

Universal Woman Sri Lanka 2026 officially began its journey with a first round of auditions, held in Colombo, marking the start of an exciting new chapter in Sri Lanka’s pageant industry.

Launching the first round of auditions

The platform aims to empower women while selecting an intelligent, confident, and inspiring representative to compete at the Universal Woman International Pageant 2026 in Cambodia, this September.

Universal Woman Sri Lanka now moves forward with the vision of creating one of the country’s most prestigious and empowering pageants while preparing to crown a queen who will proudly represent Sri Lanka on the international stage.