Page 348 - Proceedings book

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reduced capacity for water retention. Key indicators of ecological stress included the

encroachment of chena cultivation near tank bunds , canal obstructions resulting from
invasive vegetation and siltation and the abandonment of minor tanks due to

upstream degradation.

Discussion

The results of this study underscore the sophisticated design and adaptive intelligence

inherent in the ancient hydraulic systems of the Kala Oya Basin. The spatial
organization observed not only demonstrates remarkable technical prowess but also a

profound understanding of landscape hydrology. The cascading tank system, a
hallmark of these ancient engineering feats, effectively regulated runoff, minimized

erosion, and ensured a consistent supply of water throughout the year (critical factor
for sustained rice cultivation in a monsoonal climate).

However, the sediment records and the GIS-based land-use assessments clearly
highlight the inherent fragility of this delicate balance. Environmental degradation,

specifically deforestation and intensive cultivation practices, significantly disrupted

hydrological flows and accelerated the rate of sedimentation, ultimately leading to the
decline of the system. These environmental impacts were further compounded by

political and administrative changes, particularly during the post-Polonnaruwa periods
when centralized water management systems weakened. This observation aligns with

broader South Asian studies, which argue that the long-term sustainability of ancient
hydraulic systems was deeply intertwined with robust socio-political structures and

effective ecological stewardship. When such stewardship declined or when

environmental thresholds were surpassed, the resilience of the entire system was
compromised.

Crucially, this study demonstrates the power of integrating GIS and environmental
archaeology as interdisciplinary tools to reconstruct long-term human-environment

dynamics with remarkable precision. The ability to accurately map tank cascades,

correlate these spatial arrangements with historical sediment records, and
quantitatively identify ecological stress zones offers a powerful model. This model is

valuable not only for academic research but also for effective heritage management
and contemporary water resource planning.

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