Till Sun and Moon Shines [Part 15]By Eng. (Dr.) Chandana Jayawardana
Several past columns were dedicated to discuss the components of ancient small village tanks and how such components would have contributed to the sustainability of the system. Those man-made physical structures were complying with the natural water cycle, so that the principle of cyclicity is maintained. Last column was dedicated to discuss the limitation of ‘fixed boundary hydraulics’ and how our ancient village tank cascade systems might have transcended this phenomenon. Considering what we so far discussed retarding this system, the holistic approach adopted in ensuring cyclicity through various structural components in ancient small tanks cascade system could be presented as in below figure. Here, it is evident that micro scale cycles are operating to ensure water availability and soil conservation in local range, embedded with macro scale “natural hydrology cycle”.
To summarize, small tank cascade system prevailing in Sri Lanka is a live example for sustainable water utilization, considering the time of their construction and continuity of operation. Sustainability of a system is deeply rooted on the cyclic utilization of material flows operating in that system. This cyclicity should address both time and space since the original status of material flows should be attained within a reasonable time period as well as within reasonable locality. Several global scale projects have been cited to this effect where extensive geographical dissipation between the source and the point of utility prompted water usage crisis.
The micro land use related to each individual small tank in a cascade is consisting of several structural elements such as gasgommana, perahana, iswetiya or potawetiya, kattakaduwa, etc. The canals connecting the tanks to form an integral cascade system possess elements such as godawala, kuluwewa, kaliya, etc. Contributions from each of these elements towards maintaining material cyclicity were discussed, with relation to the generally accepted water flow in natural hydrology cycle. In this discussion, the efforts were made to highlight the measures adopted to maintain the locality in the processes of cylicty. Concepts such as blue water vs. green water; fixed boundary vs. moving boundary were also explored with the view of identifying paradigmatic distinctions between current hydraulic studies and the conceptual footing on which our ancient water management techniques were developed. New dimensions with respect to the water flows like infiltration and evaporation, which are considered as losses in conventional hydraulic engineering would have alternative meaning in ancient system. Only a holistic view on water utility encompassing nature, humans, flora and fauna could demonstrate the cyclic effects of such utility, ultimately leading to sustainability of the system.
Eng. (Dr.) 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.