Originally Published in Forest Cover 61- Global Forest Coalition Newsletter on May 22, 2020, International Day for Biological Diversity

By Hemantha Withanage, Centre for Environmental Justice and GFC regional focal point for Asia, Sri Lanka

Photo Credit Dam construction in Sri Lanka. Gihan Jayaweera

Ideally, building a reservoir is an environmentally friendly thing to do. It can be a good “nature-based” solution for climate adaptation, too. However, this is not the case when it comes to large, modern irrigation projects in Sri Lanka.

The Yan Oya Irrigation Project in eastern Sri Lanka was completed in 2019. It cost Rs. 39,000 million (USD $210 million) and holds 149,000 acre-feet of water (184 million cubic metres). A loan from China provided 85% of the project’s funds, and the China CAMC Engineering Corporation constructed a 2.3 km-long dam across a section of the 130 km-long Yan Oya River. The dam will provide water to nearly 8,000 hectares of rice paddy cultivation.

Unfortunately, the project destroyed more than 26 small ancient water storage tanks and over 6,000 hectares of forests both for reservoir construction and new areas of cultivation. The project’s Environmental Impact Assessment was inadequate and developers could not even identify the total land requirement during the feasibility stage. Rebuilding the ancient tank system would have been more sustainable, avoiding the project’s negative impacts and providing a better climate change solution.

Similarly, the Malwathu Oya Irrigation Project is building a 3.5 km-long dam across a section of the 164 km-long Malwathu Oya River in the North Central Province of Sri Lanka. The project will cost Rs 12,000 Million (around USD $66 million) and will destroy over 5,000 hectares of forests and more than 24 small ancient tanks. The reservoir will hold 170,000 acre-feet of water (210 million cubic metres).

According to environmentalists, rebuilding the ancient tank system in Sri Lanka would be a far better climate adaptation solution than large dams. Sri Lanka is famous for its 3,000-year-old hydraulic civilization. There are over 40,000 small and large tanks covering the dry northern and eastern regions of the country. Our ancestors knew that the limestone bedrock in the dry zone is not suitable for storing rainwater underground and constructed a unique and elaborate system of tanks and reservoirs to provide villages with clean water year-round.

In a report to the Governor of British Ceylon (now Sri Lanka) in 1855, John Baily wrote: “It is possible, that in no other part of the world are there to be found within the same space the remains of so many works of irrigation which are, at the same time of such great antiquity, and of such vast magnitude, as in Ceylon. Probably no other country can exhibit works so numerous, and at the same time so ancient and extensive, within the same limited area, as this island”.

In 2018, Sri Lanka’s tank cascade system, locally known as “Ellanga”, was recognized as one of 14 newly designated “Globally Important Agricultural Heritage Sites” by the FAO. Yet Sri Lanka continues to destroy this ancient system in the name of modern irrigation.

The Yan Oya and Malwathu Oya irrigation projects and their water storage reservoirs are not based on the same principle as the ancient irrigation system. Under the ancient system, streams were first dammed to build small tanks to keep silt from entering the larger (but still small in comparison) reservoirs. The small tanks only fed the water table. The water released from the small tanks drained through areas containing aquatic plants such as lotus and kohila (Lasia spinosa) to absorb toxins and then fed the major tanks for storage and eventually irrigation and domestic use. At least three types of reservoirs can be found in the ancient tank cascade system. This system is an age-old solution based on natural principles. Restoring the system would provide a solution to climate change and water scarcity and enhance biodiversity at the same time.

In light of this, it is very sad to see how modern engineering financed by multilateral banks, China and other bilateral investors is destroying our ancient and far more sustainable system. This shows that so-called modern nature-based solutions are not the answer to the climate and biodiversity crises the world is facing.(END)