South Asia despite decreasing rates of infectious disease, accounts for a significant proportion of their global burden. The sub-continent is also in the midst of rapid economic growth; large scale changes in land use, access to water and sanitation, and agricultural production; environmental degradation; and technological transformation, all against a background of uneven health system capacity. South Asia, defined by the World Bank as Afghanistan, Bangladesh, Bhutan, India, Maldives, Nepal, Pakistan, and Sri Lanka, is home to a quarter of the world’s population.

Trend analysis of hydro-climatic variables provide useful information for effective planning, designing and management of water resources and agricultural production. Trends in observed stream flow at upstream and midstream gauging stations (GS), Wellawaya, Thanamalwila & rainfall and temperature in the Kirindi Oya river basin were assessed using the Mann-Kendall, Modified Mann-Kendall and Sen’s slope. Average rainfalls for the two catchments and for the entire basin were computed using ‘Thessen polygon’ method.