The Sinhalese civilization was hydraulic, based on the storage and use of water for the regular cultivation of wet fields. The early Indo-Aryan settlers cultivated rice and settled along river valleys and other suitable lands. They began with simple schemes for damming rivers and storing water below them. Systems for storing water in reservoirs by tapping seasonal streams later became a feature of nearly every village; these waterworks probably were managed communally by the landowners of the village.
With the increase in royal power, the attraction of greater revenue through greater production made kings play an active role in the construction of large-scale irrigation schemes. Beginning about the 1st century, large perennial rivers were blocked with massive earthen dams to create colossal reservoirs. With increasingly sophisticated irrigation technology, water from these reservoirs was delivered through canals to distant fields and through underground channels to the capital city.
The construction and maintenance of monumental irrigation works became a regular preoccupation of kings. Among the primary functions of the central administration was the enforcement of regulations to coordinate cultivation of irrigated plots, to control the flow of water, and to collect water dues from the irrigation operators. Such effective and efficient water management led to increased productivity, which ultimately increased the power of the kings.
Some Irrigation complexes built during Anuradhapura and Polonnaruwa era.
Abhaya Weva (Basawakkulama Weva)
Kalaweva
Tissa Weva
Minneriya Tank Complex
Kaudulla Tank
Parakrama Samudraya Tank Complex