Potential to enhance the extent of paddy cultivation using domestic and municipal waste water harvesting - a case study from the dry zone of Sri Lanka

Abstract

Paddy cultivation is constrained due to shortage of rainfall or irrigation water supply. With the population growth, farmers have to increase the paddy production to meet the existing as well as future demand with the same or less land cultivated at the present. Wastewater from domestic and municipal sources which are harmless and that can be harvested can be diverted to irrigate paddy fields thereby increasing the extent of land under paddy. A study was conducted in selected Divisional secretariat divisions from Puttalam District, Sri Lanka in order to explore the potential increment of land that can be brought under paddy cultivation with the utilization of municipal and domestic wastewater. The wastewater generation was estimated based on the population and water consumption data. The extent of paddy land under minor irrigation and rainfed agriculture, potential asweddumized extent, land area cultivated in Maha (main) season and Yala (off) season and the areas harvested were collected from district agriculture department. It is noted that all the available lands were not cultivated and not harvested in both Maha and Yala seasons. Lands left without any production is high in the Yala season compared to the Maha season. Only a part of the land area is harvested from the total area sown. One of the major reasons for crop failure is shortage of supplementary irrigation water, inadequate rainfall and irrigation water. About 22% of the uncultivated lands in Maha can be brought under cultivation if 55% of the gray water generated is collected and diverted to irrigate paddy fields. In Yala season, only very small portion of uncultivated land (5% of uncultivated land) can be brought under cultivation with the gray water irrigation.