Abstract:
The most recent nationwide Iso-Yield curves, which illustrate regional variations in crop
productivity, were last updated in Sri Lanka in 1978. This lengthy gap in data is significant,
especially given the considerable changes in climate, hydrology, and agricultural practices that have
taken place over the past four decades. This study aims to update Sri Lanka's yield maps for its two
primary monsoon-driven cultivation seasons: Maha (Northeast Monsoon) and Yala (Southwest
Monsoon). To achieve this, an integrated approach is employed, combining river gauge data,
records of reservoir operational inflows and outflows, and observed agricultural production
statistics. Historical and contemporary hydrological datasets from key river basins were compiled
and analyzed to estimate irrigation water availability patterns across districts. These hydrological
indicators were statistically correlated with crop yield performance data derived from national
agricultural statistics, facilitating the spatial interpolation of updated yield distributions. Advanced
geospatial analysis techniques and GIS-based modeling were employed to delineate field zones
characterized by homogeneous yield potential, resulting in the generation of updated Iso-Yield
curves for both monsoon seasons. The findings indicate significant spatial shifts in high- and lowyield zones compared to the 1978 maps, reflecting the combined effects of climate variability,
alterations in reservoir operations, and evolving irrigation practices. The updated Iso-Yield curves
provide a more accurate representation of Sri Lanka's current agricultural productivity landscape,
aiding in precise zoning for optimized agronomic decisions, targeted irrigation scheduling, and
region-specific crop planning. This study offers a valuable decision-support tool for policymakers,
irrigation managers, and farmers, while establishing a methodological framework for future yield
mapping endeavors in monsoon-dependent agricultural systems.
