Till Sun and Moon Shines [Part 7]By Eng. Chandana Jayawardana
Village Tank Cascade Systems – a Pathway to Sustainability
During the last part of this series, we were discussing the potential of our ancient water works and structural constructions as means towards studies on sustainability. This part sill focus of one such example, the village tanks occurring in cascaded manner throughout the Rajarata plains.
Water management system prevailed in ancient Sri Lanka has been subjected to many scholarly work. These studies were initiated by administrative officials during colonial era and the general interpretation formed was that this system was a mono-functional, mega-structural utility. Storing rain water for irrigation was considered as the sole water management objective, while structural duo, earth bund and bisokotuwa, representing storage-distribution phenomenon were admired as the prominent elements. Later developments on the subject changed this perception towards multi-functional, micro-structural application with small village tanks arranged in cascade systems playing a decisive role. Now it is established that these small tanks cascade systems have been ensuring sustainable utilization of water in harmony with soil, flora - fauna and human ecosystems since their inception.
The history of this ecosystem extends back to 4th century B.C. or further according to the literal and ephigraphical evidences. Some of them are still in working order, and hence could be treated as a time tested example for sustainable water management enterprise. Intention of this paper is to explore cyclicity encompassed with water utilization in this micro, man made water management system with macro, natural hydrology cycle as the reference.
Several authorities have identified that the small tanks, distributed across dry zone landscape are not randomly located. They occur in a form of distinct cascades that are positioned within well defined small watersheds or meso-catchment basins. This is well evident in the Information Map of Water Shed Basins published by Water Management section of Agrarian Development Department in year 2008. there, 77 meso-catchment areas have been identified catering 1162 small tank cascades distributed throughout the island, with North-Western and North-Central provinces occupying the highest density.
Existence and development of these cascade systems in space and time scales are recorded to some extent in ancient epigraphical evidences. Siriweera notes the inscriptions of the first three centuries of the Christian era alone, mention more than hundred and fifty such small tanks. Ephigraphical studies by Perera and Basnayaka reveal the importance of small tanks in the various physical, social and economical dimensions such as topological distribution, economical ownership and as the subject matter of various religious offerings. An inscription dated in the reign of Kanitthatissa [AD.164-192] distinguishes three types of tanks: gamikavavi, mahavavi and danavavi. General interpretation assigned to first type is the small village tanks. The Samanthapasadika, the Buddhist Commentary on Vinaya Pitaka, supposed to be compiled in the 5th century CE, refers to large and small tanks and privately owned tanks. These historical records establish the fact that small tank is a part of water related infrastructure since ancient times.
According to Witharana there are nearly 12,120 small tanks in working condition, specially concentrated in the dry and intermediate zones. Considering these were constructed at the ancient times as previously discussed, small tank cascade systems could be treated as a live example for sustainable means of water utilization. Ensuring sustainability of a system is directly linked with the cyclicity of the material flow within that system. The next part of this series is dedicated to understand the sustainable existence of these small tank cascades, by exploring the tactics and strategies adopted to ensure material cylicity.
Basnayaka, H.T., Purana Sri Lankawe Jala Shishtacharaya, Samanthi Publishers, Ja-Ela, 2005
Perera, L.S., The Institutions of Ancient Ceylon from Inscriptions (from 831 to 1016 AD), Vol. II, Part II, International Centre for Ethic Studies, Kandy, 2005
Siriweera, W.I, History of Sri Lanka: From Earliest Times up to the Sixteenth Century, Dayawansa Jayakody & Co., Colombo, 2004
Witharana, DDP, Village Tank Categorization; Small Tank Settlements in Sri Lanka, ed. M.M.M Aheeyar, Hector Kobbekaduwa Agrarian Research & Training Institute, 2004, pp. 16-31.
Eng. Chandana Jayawardana has earned his first degree in Electrical Engineering from University of Moratuwa and then, post graduate qualifications in Industrial Engineering and Buddhist Studies. He is currently working as Design Manager, Balfour Beatty Ceylon (Pvt) Ltd, Katunayake.