May 21, Colombo: The Asian Development Bank (ADB) is supporting a major government water resources project in Sri Lanka to provide irrigational and potable water to the dry zone.
The project will divert untapped water from the Mahaweli River to feed the tanks and reservoirs in the northern dry zone to provide irrigational water full year-round, allowing farmers to plant two crops instead of the usual single crop.
Sri Lanka's ancient tanks have been built to store rain water and maximize the use of its water resources. However, monsoon flows and floods still flow into the ocean unproductively, the project leaders say.
The intention of the project is to retain this excess water and distribute it through new canals linking existing and new tanks, and reservoirs being constructed.
In effect, the project is putting in the backbone plumbing system to deliver the runoff into existing tanks that up to now have been isolated from the Mahaweli System. This will optimize the use of storage infrastructure and minimize the number of new dams that need to be built.
The project will finance about 260 kilometers of new and upgraded canals, tunnels, reservoirs, and other irrigation infrastructure by 2024.
When completed, up to 1 billion cubic meters of water will be transferred annually to irrigation systems in the northern dry zone. This will increase agricultural production significantly and strengthen water and food security.
With more reliable flows of water, farmers will be encouraged to move into higher-value crops, leading to higher incomes, the ADB says.
The project will also provide safe and reliable drinking water to northern towns and villages.
Mahaweli River is the country's largest river basin with headwaters in the southern wet zone. The water balance studies have shown that there is enough water to transfer from the Mahaweli River to quench the thirst in the northern dry zone, without affecting existing downstream water users.
The project will use remote sensing, detailed flow monitoring, and water accounting to help system managers and farmers improve water management and irrigation efficiencies.
A 3-year study will be conducted on improving system efficiencies and water productivity, or how water is used by farmers. The project will also introduce measures to strengthen water management and governance practices.