Although south-west Sri Lanka receives abundant rainfall from the monsoons, most of the island - the Dry Zone - lies in the rainshadow of the central mountains and suffers summer drought and massive autumn flooding.
Water control is therefore vital. The early chronicles speak of tanks (reservoirs) being built from the mid 1st millennium BC. Some were no more than natural ponds that were enlarged, others involved building bunds - stone or mud and timber embankments - to retain or dam the water.
Water control was particularly important for growing rice, the staple crop, which requires flooded fields.
By AD 1, some 3000 villages had tanks and at Anuradhapura there were three massive reservoirs. It is not only the scale of these constructions that is impressive but also their complexity. The water level in the reservoirs and water supply to canals was controlled by sophisticated stone sluices. The canals, some of which ran long distances, show expert knowledge of and competence in handling speed of flow and gradients.
Village tanks were probably the responsibility of the village elders, but the more massive reservoirs and canal systems were supervised by a government Inspector of Reservoirs.
