Sorabora Wewa and the Unique Sluice

Located just 1 km from present-day Mahiyangana town, Sorabora Wewa is one of the most prominent and unique irrigation reservoirs of ancient Bintanne. It is a popular stop for visitors en route to the sacred Mahiyangana Rajamaha Viharaya.

A Reservoir Without a Bisokotuwa

Historically known as the “Sea of Binthanne,” Sorabora Wewa stands out among Sri Lanka’s ancient reservoirs. It is believed to be the only surviving reservoir that does not utilize a Bisokotuwa—the vital pressure-regulating chamber found in nearly all large ancient reservoirs. The Bisokotuwa, a revolutionary invention from as early as the 4th century BCE, allowed the ancients to control water pressure and construct massive reservoirs with embankments protected from erosion.

Typically, sluice gates are installed within the embankments and work in conjunction with the Bisokotuwa. However, at Sorabora Wewa, the builders ingeniously bypassed this method by cutting a deep canal through a natural rock formation away from the bund. This rock sluice served the same function without the need for additional structures, as the rock itself withstood the immense pressure of water.

Construction and Scale

The reservoir was constructed by damming the Diyawanna Oya with a massive embankment measuring 1,590 feet (485 meters) in length and 40 feet in height. The embankment is approximately 11 feet wide. At full capacity, the reservoir spans about 1,100 acres (4.5 sq km) and holds 11,800 acre-feet (approximately 14.6 million cubic meters) of water. The rock-cut sluice gates, located away from the embankment, are about 5 feet wide and display expert craftsmanship.

The Legend of Bulatha – Builder of Sorabora Wewa

According to tradition, Sorabora Wewa was constructed in the 2nd century BCE by a lesser-known but mighty general named Bulatha during the time Prince Gemunu was campaigning against the Tamil king Elara. As the prince and his ten famed warriors advanced toward Anuradhapura, they temporarily camped at a village called Kadali Pathra—modern-day Keselpatha—near Mahiyangana.

Bulatha, a strongman from Kiripattiya village in Ududumbara, joined Gemunu’s forces at this point. He was entrusted with the daily task of collecting and delivering various provisions: treacle from Meemure, milk from Kiripattiya, betel leaves from Kevulgama, and areca nuts from Puwakpitiya (now Popepitiya), navigating the treacherous Kosgolla mountain pass that connected Ududumbara to Minipe and was frequented by pilgrims traveling to Mahiyangana.

While traversing this route, Bulatha noticed a stream flowing between two hills and envisioned building a reservoir there to irrigate thousands of paddy fields. Despite his demanding duties, he began constructing the embankment on his own during his free time. His extraordinary strength was legendary—his mamoty (spade) was said to be ten times larger than a typical one, and his earth basket was equally massive.

His wife, known for her strength equivalent to 20 women, supported him tirelessly. She would cross the dangerous Kosgolla Pass daily to bring him meals. Witnessing the struggles of countless pilgrims using this rugged route, she resolved to improve the path by building a flight of stone steps. Each day, as she brought food to Bulatha, she laid a few stone steps along the path.

Two Monumental Achievements

Eventually, Bulatha completed the Sorabora Wewa—featuring a 40-foot-tall, 11-foot-wide embankment and an innovative sluice cut through natural rock. Simultaneously, his wife had constructed around 2,000 stone steps across the Kosgolla pass to aid Mahiyangana pilgrims.

At the same time, King Dutugemunu (161-137 BCE) completed the renovation of the Mahiyangana Stupa following his victory over Elara. On the day the king ceremonially reopened the stupa, Bulatha revealed his secret project to the king and queen, proudly showcasing both the reservoir and the monumental staircase built by his wife.

Royal Recognition

Impressed by Bulatha’s unassisted effort, King Dutugemunu removed his royal cape and placed it on Bulatha, appointing him as a general and gifting him a village named Udathwewa. Queen Viharamahadevi was equally moved by the strength and devotion of Bulatha’s wife. She gifted her a necklace and appointed her as the chief of the queen’s personal security.

The village awarded to Bulatha, today known as Udaththawa, is located about 8 km north of Hasalaka. Remarkably, ruins of a large reservoir exist here, built in a style similar to Sorabora Wewa, featuring a rock-cut sluice and no Bisokotuwa. These two reservoirs—Sorabora Wewa and Udaththawa Wewa—along with the Erupothana Wewa at Mahakachchakodiya, are the only known ancient reservoirs in Sri Lanka that employed this rare rock sluice technique, a testament to Bulatha’s ingenuity.

Legacy of the Stone Steps

The ancient stone stairway over Kosgolla built by Bulatha’s wife still survives in parts and is now known as Galpadipela.

The begining of the rock cut sluice seen from the top of the rock at Sorabora Wewa

Primary Source : Sorabora Wewa Nodutu Ess Motada Pin Kale
by Dharmasena Mahawela

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