The mahaweli river is the longest river in Sri lanka, stretching over a distance of 335 km (208 miles) from its source in the horton plains to its mouth in the Indian Ocean. The river plays an important role in the agricultural, hydroelectric, and cultural development of the country.

Historically, the Mahaweli River has been an important waterway in Sri Lanka. It was used for transportation of goods and people, and was also a vital source of water for irrigation. However, in the 20th century, the government of Sri Lanka initiated several projects to harness the power and potential of the river, leading to significant changes in its course and usage.

One of the most notable projects on the Mahaweli River is the Mahaweli Development Program, which was launched in 1978 with the goal of utilizing the river's potential for irrigation, hydroelectric power generation, and industrial development. The program involved the construction of several dams, reservoirs, and canals along the river, which have helped to significantly increase the country's agricultural productivity and provide a reliable source of electricity.

The Mahaweli Development Program has also had significant environmental and social impacts. The construction of dams and reservoirs has resulted in the displacement of thousands of people and the flooding of large areas of land, leading to the loss of valuable habitats and biodiversity. However, the program has also led to the protection and restoration of several ecosystems, such as the knuckles Conservation Forest and the wasgamuwa national park.

In addition to the Mahaweli Development Program, the government of Sri Lanka has also initiated several other projects aimed at promoting sustainable development along the river. These include the Mahaweli Water Security Investment Program, which focuses on improving water management and infrastructure, and the Mahaweli River Basin Integrated Development Project, which aims to enhance the livelihoods of local communities and promote sustainable land use practices.

Despite the challenges and controversies surrounding its development, the Mahaweli River remains a vital resource for Sri Lanka, providing water, energy, and livelihoods to millions of people. Its history and ongoing development serve as a reminder of the complex and interconnected nature of environmental and social issues, and the need for sustainable and equitable approaches to development.