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.

Another example of the insufficiency of relying on theoretical and book knowledge is ignoring the real problem(s) in such situations.  In this context, the work and insights of pioneering scholars and engineers such as Joseph Needham and DLO Mendis, modern engineers who understood the value of ancient hydraulic engineering, are invaluable. 

Each large irrigation construction in Sri Lanka fails to incorporate their suggestions and wisdom. Their recognition of the brilliance of Sri Lanka’s ancient water civilization reminds us that looking back can often provide the best solutions for moving forward.