Prof. Sunil Wimalawansa

Water has always been the cornerstone of human survival and agricultural development. In ancient Ceylon—modern-day Sri Lanka, once known as Hela—visionary engineers and kings created one of the world’s most advanced irrigation networks. This remarkable hydraulic civilization demonstrated profound foresight, engineering skill, and ecological harmony, establishing a sustainable system that supported thriving communities and bountiful agriculture for centuries.

The evolution began with simple rain-fed agriculture, which gradually transformed into a sophisticated rainwater harvesting system. Small village reservoirs, known as wewa,” were at the heart of this transformation, ingeniously constructed to collect and store monsoonal rains. These tanks were more than just water storage units—they were sacred, often built alongside Buddhist temples, symbolizing the unity between nature, faith, and daily life.

Among the most significant innovations were the sorowwa” (sluices), bisokotuwa” (regulation chambers or access towers), spillways, and embankments—sophisticated hydraulic mechanisms that allowed precise water control. These technologies enabled the creation of large cascading tank systems, in which water from one tank overflowed into the next, ensuring consistent irrigation throughout the year. These interconnected reservoirs transformed arid regions into fertile farmland, supporting rice cultivation and securing food supply for millions.

Strategic river diversions, permanent weirs, and an expansive network of channels were added later to enhance the functionality of these reservoirs. These innovations reflected technical brilliance and an understanding of sustainability, water conservation, flood control, and soil retention. This holistic approach, refined over centuries, formed a resilient ecological framework that balanced human needs with nature.

Regrettably, modern engineering approaches have often dismissed or neglected this ancient wisdom, (falsely) claiming that they are inefficient. Driven by large-scale development priorities, many modern water infrastructure projects have ignored the time-tested principles of Ceylon’s hydraulic civilization. Recent projects like those at Udawalawe and Lunugamvehera exemplify the consequences—poor planning, soil degradation, sinking lands, water wastage, and frequent flooding.

Besides, the mentioned constructions created land subsidence—a gradual settling or sudden sinking of the Earth’s surface owing to hydro compaction, subsurface movement of earth materials, sinkholes, and thawing permafrost. The focus of modern hydraulic engineering was providing water for agriculture. Consequently, rather than focusing on practical and worthwhile, it implemented ‘mechanical’ solutions (ignoring the nature), sidelining the integrated ecological balance that ancient systems achieved. It is a classic failure due to egotistic and improper prioritizations.

Hydrology today must reclaim its original purpose—not merely manipulating water flow but managing water holistically for agriculture, flood mitigation, and ecosystem preservation. Reviving and integrating ancient Sri Lankan irrigation knowledge with modern innovations offers a pathway to sustainable water management, food security, and economic revitalization.

Each major modern irrigation project in Sri Lanka has consistently failed in the intended benefits and humanistic aspects by the failure to incorporate the invaluable insights of pioneering engineers such as D.L.O. Mendis and Joseph Needham, along with dedicated professionals like Mr. Godfrey de Silva—former Chief Irrigation Engineer in Kandy and later Chairman of the Mahaweli Authority—and a few other pragmatic engineers who deeply valued Sri Lanka’s ancient hydraulic heritage. These experts recognized the brilliance and sustainability of the centuries-old water systems, emphasizing ecological harmony, community-driven management, and long-term resilience.

I remain deeply grateful to these visionaries for sharing their knowledge, which we have applied over the past four decades through charitable projects focused on water and agricultural initiatives, including the provision of potable water to rural communities affected by chronic kidney disease of unknown origin (CKDu) (now called, CKD of crystal-tubular nephropathy (CKD-CTN) [https://pubmed.ncbi.nlm.nih.gov/37408060/; DOI: 10.1186/s40001-023-01162-y]. 

Sadly, modern engineering has largely disregarded this rich legacy, resulting in inefficient infrastructure (geo-genic and Geo-Bio issues), increasing water scarcity, and significant environmental degradation. The prevailing approach has been narrowly focused on transporting water from point A to point B, while neglecting critical elements such as ecological balance, soil conservation, and groundwater recharge.

A striking example is the high prevalence of CKD-CTN—a likely a “geogenic” issue resulting from groundwater contamination—in Mahaweli-affected (and other) regions, such as Dehiattakandiya. This emerging public health crisis reflects the consequences of poorly planned water interventions that ignored traditional ecological safeguards. The failure to incorporate ancient wisdom and holistic water management practices has led many large-scale irrigation projects to fall short of their intended benefits, ultimately causing long-term harm to both communities and ecosystems.

Conclusion:
The ancient irrigation systems—refined over millennia with engineering precision and environmental foresight—offer time-tested, practical solutions. Reintegrating these foundational principles with modern innovations is not only wise but necessary. Such an approach could restore ecological balance, ensure sustainable food and energy security, and strengthen resilience in the face of climate change. Honoring and learning from Sri Lanka’s ancient water legacy is more than a tribute to the past. It is essential for building a sustainable and equitable future, as well as ensuring food sustainability—a practical necessity for resilient development.