Potential to increase the area under paddy cultivation with domestic and municipal wastewater irrigation in Kurunegala District

Use of domestic wastewater for agriculture was a traditional practice in Sri Lanka where leafy vegetables and medicinal plants were cultivated in backyards. The use of domestic and municipal wastewater could be an environmentally sound means of wastewater disposal and could reduce environmental pollution if utilized for paddy irrigation. This practice could also help to increase the economic productivity of the water and land. Therefore a study was conducted in selected Divisional Secretariat Divisions in Kurunegala District in order to explore the potential for land to be brought under paddy cultivation with the utilization of municipal and domestic wastewater. The quantity of wastewater generated was estimated based on the population and water consumption data. Data on the extent of paddy land under minor irrigation and rain-fed agriculture, potential cultivable land extent (known as asweddumized area), land area cultivated in maha (wet) and yala (dry) seasons, and the areas harvested were collected from the District Agriculture Department. It is noted that not all the available lands were cultivated and harvested in both the maha and yala seasons. The area of land that is not used for any crop production is higher in the yala season than in the maha season. In addition, only a part of the land area is harvested from the total area sown. Major reasons for crop failure are inadequate rainfall and shortage of supplementary irrigation water. The difference between the cultivable (asweddumized) extent and harvested extent shows the land that can potentially be brought under irrigation using municipal and domestic wastewater. The amount of land that can be so irrigated is much higher closer to the city where the storm water and other forms of wastewater are drained through common canal systems. Depending on the quantity and quality, and the availability of fresh irrigation water, municipal wastewater can be either diluted with irrigation water to meet the total irrigation water requirement, or can be used without any dilution. In addition to the increment of the land area under cultivation, there is a possibility of increasing the cropping intensity.