Agent-based modeling for sustainable water resource planning: insights from the village tank cascade system

Abstract

Village Tank Cascade Systems (VTCSs) in Sri Lanka represent long-standing, community-managed irrigation systems that operate through tightly coupled hydrological, agricultural, and governance interactions. This study applies an Agent-Based Modelling (ABM) approach as an analytical framework to examine water-sharing dynamics within a representative VTCS in Sri Lanka, using a selected tank cascade as a case-based illustration for identify the complexity of the system. Rather than generating predictive estimates for modelling, the study focuses on hypothetical case for application of ABM through the understanding of the complexity of the VTCS. The analysis compares non-sharing and proportional water-sharing arrangements under identical climatic conditions to explore how governance rules influence storage distribution and cultivation outcomes. Increasing climatic variability, particularly during the Yala season, intensifies water scarcity within cascades, while the results show that governance-based redistribution of upstream storage reduces downstream vulnerability during water-scarce periods through adaptive and sustainable decision-making. The findings highlight the central role of governance in shaping how scarcity is managed within VTCSs and demonstrate the usefulness of ABM for exploring adaptive, people-centred water-sharing arrangements which highlights Sri Lanka’s traditional irrigation system’s sustainable use of water governance and demonstrates how interaction-based analysis can support adaptive, equitable water-sharing governance in interconnected tank cascade systems.