Farakka Barrage

     Background Information
     Discussion and Research Questions
     Responses
     Further Resources

Background Information

Early in the 19th century the British Government in India saw the benefits of managing Ganga's flows.  A famine in 1837 and 1838 led to the construction of the Ganga Canal, beginning in the sacred city of Haridwar and carrying water by gravity over 400 miles to irrigate the fields of Uttar Pradesh.  This diversion has certainly saved thousands of lives by preventing famines that would otherwise inevitably follow a devastating drought.  The success of this action led to many more projects up and down the length of Ganga and the other rivers of India.  And yet, this security comes at a price.  As with so many other dams, siltation has caused problems in the reaches of the river above the barrage, restriction of flows has increased the concentrations of pollutants and downstream users suffer from the loss of the water. 
top of page

Discussion and Research Questions

1. Major projects involving the management of water resources have enjoyed considerable support from governments and international development organizations. What are the primary reasons for the construction of dams and barrages in developing countries and why are these seen as important for a region's economic growth?

2. Environmental problems associated with such major water management projects are common and well-documented. Well known examples include the Aswan High Dam in Egypt, the James River Project in Canada, and many are concerned about the Three Gorges Dam restricting the flows of the Yangtze River in China. What environmental factors are most important in assessing the long-term effectiveness of a dam?

3. Funding of such major water management projects is under attack from national and international environmental groups. What is the basis of the cost-benefit analysis of the construction of a dam and can these be mitigated with careful design?

top of page

Responses
Question 1:  Dams and barrages are constructed to increase water supplies in areas with seasonal shortages, provide a source of electricity for an area undergoing industrial growth and/or to reduce flooding in downstream areas allowing for agricultural use of a river's floodplain or increased land development. All of these can lead to economic growth or an improved standard of living for populations in developing countries. In many cases, international support has led to extensive investment in such projects which has enriched governments and individuals in the recipient countries.

Question 2: An evaluation of a dam project requires the examination of three types of impact:

Immediate environmental, social and cultural effects

• Potential disruption of migration routes for aquatic species, especially anadromous and catadromous fish (salmon, alewife, eels).
• Habitat fragmentation for species with large area requirements.
• Habitat changes associated with reductions in flow rates, increases in water temperature, changes in sediment flows, and changes in water depths.
• Loss of wetland and terrestrial habitats adjacent to the river
• Increases in pollution as transport is reduced and materials accumulate behind the dam
• Increases in the transmission of water borne diseases such as schystosomiasis and others
• Flooding of upstream lands and the relocation of inhabitants and loss of agricultural lands
• Sites of historic and cultural importance are frequently located along rivers. Dam or barrage construction can result in the direct loss of these features and can prevent future archaeologic exploration in an area.
• Downstream effects are many, and include the loss of water during dry periods, and the loss of flooding important to maintaining the productivity of agricultural lands in the flood plain
• Elimination of important commerce routes occurs when boats are prevented from traveling upstream

While the above list is long, it is certainly not complete, with many site specific concerns appearing with new proposed projects.

An assessment of the long-term potential of the dam must consider

• The accumulation of sediments behind a dam has historically reduced to ability of the structures to retain water. Lands subject to high levels of erosion or rivers characterized by large amounts of silt are vulnerable to a rapid loss in storage capacity.
• Eutrophication of the waters behind the dam resulting from the increased concentrations of nutrients can result in a reduction of water quality and the rapid loss of storage area as vegetation comes to dominate the water.
• In arid regions evaporative losses can cause significant reductions in the water storage capacity and can increase salinity of a region

An assessment of future risk associated with the dam

• While the construction of a dam reduces downstream flooding, the newly occupied lands are subject to catastrophic loss should the dam fail.  Dramatic evidence of this can be seen in the floods in India described in references below and the devastation caused by Hurricane Katrina in the southeastern United States in September of 2005
• The weight of the impounded water can cause geologic instability, especially important in seismically active regions.

Question 3:  The World Bank and other international agencies continue to fund dam projects throughout the world although there is evidence of greater sensitivity to the issues raised above. Mitigation can reduce the impacts described, although many measures are costly and some meet with only mixed success.

• Sedimentation – A reduction in the effects of sediment accumulation can be achieved by incorporating engineering solutions into the design of the dam, implementing management practices to reduce erosion in the watershed of the river, or committing to periodic dredging of the material above the dam. All such solutions are problematic, with the success reduced by technological limitations or added costs associated with their implementation.
• Habitat Issues – The use of fish ladders in dams and barrages can be effective for some species of anadromous and catadromous fish, however they are ineffective for many species. While habitat creation and restoration can mitigate the loss of critical habitats, such practices depend on the availability of sites suitable for such work and the resources needed to create the new habitat areas. It is rare for both of these to be available at the location needed.
• Commercial Issues – The disruption of trade routes associated with dam construction can be mitigated by the inclusion of locks adjacent to the dam. Such structures significantly increase the costs of the project, slow the speed of the transport and depend on access to adequate land for construction.

top of page

Link to Classroom Activity – Increasing water supplies

top of page