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Saturday, November 07, 2009

Lakes in Sri Lanka

The rivers of Sri Lanka originate in the central highlands. From there they descend to the plains and empty into the sea. The rivers are typically unnavigable in their higher reaches, where they flow swiftly and turbulently through highly eroded passages to the plains below. Many rivers descend over steep cliffs, forming spectacular waterfalls. In their lower courses, the rivers slowly meander through flood plains and deltas.


The longest river of Sri Lanka, the Mahaweli, traverses a course of about 330 km (about 205 mi). It flows northeastward across the central highlands and empties into the Bay of Bengal near the port of Trincomalee, on the eastern coast. The country’s second longest river is the Aravi Aru, traversing about 220 km (about 135 mi) on a northwestward course, from the central highlands to the Gulf of Mannār.

Sri Lanka has no natural lakes. Dams on the Mahaweli and other rivers have created large reservoirs. In addition, a series of small reservoirs called tanks dot the north central plains, storing water during the dry season. Some of the tanks were constructed as many as 2,000 years ago.

Much of Sri Lanka is arid and has only a few permanent rivers. However, the southwestern region's "wet zone" is characterised by numerous rivers that arise in the high mountains of the central part of the island.
These diverse river basins support endemic populations of aquatic plants, bivalves, and fish.

Sri Lanka's known freshwater species include 90 fish (with twenty-six endemics) and 21 crabs, yet ongoing studies suggest that the number of undescribed species is potentially quite large. Most of these fish are small and highly specialised to their habitat.

The islands Buddhist civilization produced skills of hydraulic engineering capable of building some of the largest man made irrigation works in the world. Many still provide water to the thousands of acres of paddy fields an urban need. The skills of our engineers in this branch is clear from the historical evidence such as the invitation made to Sri lank an Engineers in the 8th century by a Kashmir kin to form a lake in his Country.

Our ancestors more than 3000 years ago has seriously considered this concept of water storing and delivery. It is evident from the gigantic reservoirs like “Parakrama Samudra”, “Kalawewa”, “Minneriya”. etc and canal systems of “Elahera’, “Yoda Ela”etc. Unfortunately due to he invasions since the Anuradhapura Era up to British period and epidemics caused all the development and technical skills of went in to wilderness. As a result Sri Lanka had to implement a new agriculture development program n the 19th century as a new enterprise.

Kalawewa


Built in 5th century AD 44.25 hectares in extent Length and the size of the dam are 5.6 km and (13-19) m Jaya Ganga (Yoda Ela)
This work of ancient Sri Lankan is considered as engineering wonder in irrigation. This stream is 54 miles long and constructed to supply water from Kalawewa to Thissa wewa in Anuradhapura. Evan Nowadays irrigation engineer�s wonder how the engineers of that era could manage to keep the slope of first 17 miles (27.2km) at 6cm per 1.6km (1 mile)


Parakrama Samudraya

Polonnaruwa boasted one of the largest and most spectacular of Sri Lanka’s ancient tanks, the “Parakrama Samudra” or the Sea of Parakrama.
It was built by king Parakramabahu the 1st. One of the greatest of the Singhalese rulers. The bound of the Parakrama Samudra was nearly nine miles long and rose to an average height of 40 feet. Its 5,600 acres of water irrigate an estimated 18,200 acres of paddy land.



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