Amid the ongoing dry weather spell, ensuring an uninterrupted supply of drinking water has become a crucial concern, despite the heavy rainfall experienced earlier under the southwest monsoon. 

Showcasing the gravity of the situation, the National Water Supply and Drainage Board (NWSDB) earlier this month announced water supply interruptions in several areas as a result of the ongoing severe dry weather and urged the public to use water sparingly and responsibly.

The board said that water levels in key reservoirs were rapidly dropping due to the prolonged drought, while water consumption had surged as people coped with the heat. It further requested people to minimise activities such as washing vehicles and gardening, while using water only for necessary daily tasks.  

Nevertheless, speaking to The Sunday Morning, NWSDB General Manager Eng. T. Barathithasan assured the public that there was no drinking water shortage at present, saying: “We have spread awareness and people have reduced consumption.”

He added that should the dry weather persist, the board may consider reducing the duration of water supply from the current 24-hour provision to manage resources. 

The scale of the problem 

Despite Sri Lanka boasting a hydraulic civilisation, with ancient villages and communities having been designed around water sources, today, around one-third of the population is vulnerable and deprived of water sources, according to the United Nations Development Programme (UNDP).

This is a stark reversal from its ancient cascade system of tanks and diversion canals, with in-built efficient and equitable socio-technical water management methods, which enhanced the long-term development of not only the water sources but also the surrounding natural resources on which the communities and their livelihoods depended.

The UNDP has cautioned that Sri Lanka remains off-track in achieving water security, making the call for action on water resilience more urgent as climate challenges loom. Its report titled ‘Understanding Multidimensional Vulnerabilities: Impact on People of Sri Lanka’ further outlines that water is the second greatest contributor to vulnerability in the country. 

“Nearly half of Sri Lanka’s population, 48.8%, lack disaster preparedness, a key vulnerability factor aggravated by accelerating climate risks, while 35.6% are vulnerable and deprived of water sources, compounding the impacts of the poly-crisis, raising significant concerns in the context of El Niño’s and La Niña’s potential impacts coupled with the effects of climate change in Sri Lanka.”

While communities in the dry zone face chronic struggles with water scarcity, especially in the northern region due to regional discrepancies in water equity and accessibility, the Food and Agriculture Organization also notes that Sri Lanka is categorised as ‘highly water stressed’.

Attributed to land use changes

Given that periods of heavy rainfall do not appear to fortify Sri Lanka’s water supply against ensuing dry periods, this raises questions about the country’s water resources management systems and infrastructure.

University of Moratuwa Hydraulic and Water Resources Engineering Division Professor in Civil Engineering Lalith Rajapakse, who is involved in agencies promoting water conservation and management as the Director of the UNESCO Madanjeet Singh Centre for South Asia Water Management, pointed out that Sri Lanka faced water scarcity even after periods of heavy rainfall due to significant land use changes. 

“In the past, after the rainy season, the water level in household wells remained unchanged for about three to four months. But now, the water level drops immediately after the rainfall season. This is because we have changed land usage in source catchments,” he said. 

He explained that from these upstream catchments, rain water entered into subsurface layers and slowly recharged wells, rivers, and streams downstream. 

According to him, increasing urban development has drastically altered the land’s ability to absorb water. With the clearing of vegetation from upstream source catchment areas and the increase of impermeable land cover such as roads, roof cover, yards, pavements, etc., water is no longer able to infiltrate the ground. 

Instead, water flows swiftly overland, being diverted to drains, streams, and rivers and reaching the ocean, often within 10-15 minutes after a rainfall event. This swift runoff leaves no room to replenish groundwater. 

As a result, groundwater levels, which rely on gradual infiltration, receive minimal replenishment during rain events, causing them to drop sharply after rainfall to minimum level.

As such, Prof. Rajapakse said that rainwater harvesting was encouraged in the dry zone in order to allow more water to seep into subsurface layers, ensuring that groundwater enriches wells and streams downstream even months after rainfall events. 

Man-made and climate change impacts 

Sri Lanka’s ancient cascade irrigation system of interconnected small reservoirs that naturally harvest rainwater is no longer able to cater to the full spectrum of the country’s modern day population needs. In addition, Prof. Rajapakse also noted that man-made impacts had led to the destruction of some of these cascade systems. 

He pointed out that changes in rainfall patterns also contributed to the severe water scarcity during the dry period. “Rainfall patterns have changed. Earlier, we had three to four months of dry season followed by longer wet periods. However, wet periods are getting shorter, with intense rainfall occurring within a short period. Meanwhile, dry periods are getting extended, with long periods of drought.”

Further, he noted that with most of the major reservoirs being partly filled with floating sediment, they lacked full capacity at the moment. However, if this ancient irrigation system were to be restored, it would help in water conservation to a significant extent, a task that the Irrigation Department and various other national organisations are attempting, according to Prof. Rajapakse. 

Need for policy support

The increased population and urbanisation points to a crisis in the offing, given the growing pressure on water resources. 

“Rainfall itself is not uniformly distributed and on top of that, when we don’t exact water uniformly, it creates water scarcity,” Prof. Rajapakse noted. 

According to him, this calls for a policy to protect source catchments – the upstream forested parts of highland areas where most of the rivers and streams originate, which carry water downstream to areas with higher population density. 

“Sri Lanka has been trying to introduce a water policy from the 1960s or 1970s, but it was unsuccessful due to various reasons. During the dry period last year, there were many arguments on whether to allocate more water for power generation or irrigation. If we have a national water policy, we can avoid such confrontations entirely,” he added. 

Further, he noted that the practice of water conservation should be inculcated among the population, since water could no longer be treated as a free commodity, unlike in the past when the population was less dense and there was sufficient water to fulfil all needs. 

“For instance, if 70-80% of water resources are allocated for irrigation, we will be using water that can be used for other purposes – such as power generation and drinking water – for irrigation instead. We should therefore start using smart irrigation practices where we can cultivate paddy without wasting water. We should also go for crop types and patterns that can save water,” Prof. Rajapakse said. 

He noted that there should also be a household-level endeavour to undertake rainwater harvesting which would support groundwater enrichment, ensuring that wells retain more water.

Efforts to improve storage 

Against this backdrop, according to NWSDB General Manager Barathithasan, the board is coordinating with the Irrigation Department and Mahaweli Authority given the prevailing dry season. He attributed the current scarcity despite the recent rains to certain incomplete projects.  

However, with the construction of the Basnagoda Reservoir and with the extensions almost at the completion stage, he gave an assurance that the drinking water scarcity in certain areas would be resolved.   

“We have now restarted the Kalu Ganga project that was stopped due to funding issues caused by the economic crisis. Its completion will take another five years and we will be able to add additional capacity,” he added. 

The NWSDB is also expecting funding for the Ambatale Water Treatment Plant, which the General Manager opined would solve the drinking water issues of the Western Province. 

In terms of storage capacity for other regions, Barathithasan outlined the dedicated reservoirs being constructed, such as Per Aru in Vavuniya and the Basnagoda Reservoir in the Gampaha District. The current focus is on a reservoir at Pali Aru for the dry areas in the region.

“The Government is also focusing on the Malwathu Oya Reservoir, which is under construction. Once these reservoirs are established, the dry zone areas will benefit in future with continuous water supply mainly for drinking as well as irrigation purposes to a certain degree,” he said.