Sustainability of Village Tank Cascade Systems of Sri Lanka: Exploring Cascade Anatomy and Socio-Ecological Nexus for Ecological Restoration Planning

Abstract

Village Tank Cascade Systems (VTCSs) in the Dry Zone of Sri Lanka have evolved as sustainable ecosystems through human interventions to ensure water availability and other services for people and their environs during the last few millennia. However, VTCSs are vulnerable to global environmental changes resulting in continual deterioration of ecological health and hydro-socio-ecological status, crucial for the food and livelihood security of rural farming communities in the dry zone. This paper seeks to explore resource systems of the Mahakanumulla VTCS located in Anuradhapura district of Sri Lanka to (i) identify the spatial metrics linked to the sustainability and socio-ecological resilience of the VTCS, and (ii) determine interactions among system elements and their impacts on productivity and restoration challenges. The spatial analysis was conducted using a Digital Elevation Model (DEM), recent digital topographic map layers and Google Earth images to understand the spatial distribution and ensemble of tank environs. Participatory field assessment data were also used to determine socio-ecological nexus and factors that contribute to the reduction of ecological productivity of VTCS. The study revealed that the ensemble of tank environs is significant for providing regulatory and supporting ecosystem services (ES) and synergistic relationships with provisional ES of the VTCS. Results also revealed that the complex land-water-biodiversity-climate and food nexus that determines the productivity of the VTCS could be adopted in VTCS ecological restoration planning. The study presents a comprehensive framework to analyse causal factors and processes leading to reduction of overall productivity linked with variables of socio-ecological properties, vulnerability and resilience of the VTCS landscape.