Aguwewa in cascade systems: does it serve the purpose

Abstract

The Sri Lankan traditional Irrigation Systemsare unique and there are number of tanks which fulfil different specific purposes. Aguwewa is one of those tanks, which is used to prevent siltation, located within the catchmentof the larger village tank. A segment of precipitation received in the catchment is retained in Aguwewa before feeding the larger reservoirs. Thereafter major reservoir is fed by seepage or spilling. However, soil erosion is critical and it causes heavy siltation in tanks due to extreme weather conditions, high intensity rain falls, deforestation of catchment, high velocity runoffs. This paper specifically emphasizes on Aguwewa in Cascade Systems and closely examines whether it fulfils its purposes and impacts to the cascade systems within present scenarios. Comprehensive literature review and RS and GIS data were used to investigate the siltation of Aguwewa in Kala Oya basin. Changes of shapes and sizes of tanks and disappearance of “perahana’’ and wind breaking trees were noted by field investigations. It was noted that the traditional irrigation systems are under threat due conversion of Aguwewa into small irrigation tanks of low productivity as a result of the ignorance of the functionality of this type of tanks. Therefore, it is important to investigate and perform mitigations on this age-old method, for revitalizing the functionalityofAguwewa.