The subject of irrigation and ground-water supply in South Asia has remained close to the heart of B.H. Farmer since the 1950s. In particular, his early contributions on rainfall and water supply in the Dry Zone of Sri Lanka (Farmer, 1951, 1954, 1956a) and on ‘Land use lessons learnt in Madras applicable to the Dry Zone of Ceylon’ (Farmer, 1956b) stand unparalleled in this field even today, not only for their academic content, but also because of the vistas they opened for further research and for actual water resources development in the areas concerned. The intention of the writer in presenting this chapter, as one who has had the privilege of direct access to the wealth, of Farmer's academic experience, is to review and update the knowledge on this important subject in relation to those lands where Farmer made his pioneering studies, namely, the Dry Zone of Sri Lanka, and the Tamil Nadu of South India. The essay also focusses attention on rice fields and Green Revolutions which have represented Farmer's most recent research interests.

History of Sri Lankan irrigation

For centuries irrigation had been an art, a science, and a way of life to the people living in the drier areas of South Asia. Many cities and settlements emerged and flourished in irrigated hinterlands. In some cases the dependence of communities on irrigation was so heavy as to warrant the use of the term ‘hydraulic societies’ by certain scholars to describe such civilizations (Leach, 1959; Gunawardhana, 1979). On the other hand highly developed civilizations have collapsed and disintegrated due to the decay of these stupendous irrigation systems (Murphy, 1957).