Let the rivers flow freelyAdmin
All studies carried out so far to assess the impact of the Tipaimukh dam are confined within the political boundaries of India and Bangladesh. For example, the EIA and EMP done by NEEPCO in 2007 do not extend beyond the border of India; similarly, the FAP-6 study (1994) and IWM study (2007) are limited in scope within the boundary of Bangladesh. Besides, both FAP-6 and IWM studies are based on sketchy information and assumptions, writes Md Khalequzzaman
by Md Khalequzzaman
THE Tuivai-Barak-Surma-Kushiyara-Kalini-Ghorautra-Meghna river system is an integral part of the same watershed. To assess the impact of any upstream water control structure, such as the Tipaimukh dam or the Phulertal barrage, in a downstream location, one needs to carry out a detailed environmental impact assessment in the entire watershed. All studies carried out so far to assess the impact of the Tipaimukh dam are confined within the political boundaries of India and Bangladesh. For example, the EIA and EMP done by NEEPCO in 2007 do not extend beyond the border of India; similarly, the FAP-6 study (1994) and IWM study (2007) are limited in scope within the boundary of Bangladesh. Besides, both FAP-6 and IWM studies are based on sketchy information and assumptions. The water level in a downstream location will depend on the amount of water released from the dam, which is not known to anyone in Bangladesh. In such a situation, it is not possible for any water-modelling software to accurately predict the water levels during different seasons in Bangladesh.
In the following few paragraphs, the results of the FAP-6 study are analysed in the context of watershed-based water resources management plan, keeping the interests of people living in the haor region in greater Sylhet and Mymensingh districts. The study was accessed on the internet: http://bicn.com/wei/resources/nerp/iee/10-ch8-FWO-impacts.htm.
Hydrology section of the report states, ‘Data used in the engineering analyses included existing topographic maps, historic climatological and hydrological records, river and khal cross-sections surveyed by BWDB Morphology Directorate and by SWMC, BWDB reports, MPO reports, personal field observations, and interviews with project area residents, and the recommendations of local representatives and BWDB officials.’ The above data were collected by organisations in Bangladesh, and are not adequate to understand the run-off to river flow characteristics in a river without incorporating data from the upper reaches in India.
Regional impacts section of the report states, ‘A number of limitations of this exercise should be kept in mind. Regional hydraulic and hydrologic processes are extremely complex, as is the model itself. Information on Tipaimukh Dam/Cachar Plain irrigation design and operation is sketchy. ....Therefore, the modelling results should be considered to be indicative of the changes which are to be expected rather than being absolutely correct.’ Life and livelihood of millions of people living in the haor region should not be decided based on sketchy data and limited information.
The impact of a potential break in the Tipaimukh dam is summarised as follows, ‘Previous experience demonstrates that modelling can reproduce dambreak flood wave characteristics reasonably well if the failure mode is adequately calibrated. We cannot and do not claim adequate calibration for these illustrative calculations.’ The study did not have data necessary to predict the nature of dam break, yet the proponent of the dam concluded that the dam break will result in a one-metre wave crest at Amalshid, Sylhet. If the dam breaks due to an earthquake then it will not take 48 hours for the dam to collapse, rather it will take minutes, resulting in a much worse situation.
With regard to possible rainfall and flooding trends the report mentions, ‘Over the period 1901 to 1991, the shape of the regional rainfall pattern was remarkably stable, but annual rainfall increased moderately (10%), and its variability from year to year increased markedly (50%). Also, over the period 1964 to 1989, one-day rainfalls increased rapidly (70%).’ The Global Circulation Models for climate change predict an increase in rainfall during rainy seasons and a decrease during lean seasons in the Indian subcontinent.
The report further states, ‘Based on this information it is clear that significant impacts on the region will result from implementation of the Tipaimukh dam and Cachar plain irrigation scheme. During an average flow year these impacts would include: Flood flows on the Barak River will be moderated, with peak flows at Amalshid being reduced by about 25% and flood water volumes being reduced by 20%. The corresponding water levels at Amalshid would be reduced by about 1.6 m.’ Decrease in water level by 1.6m (5.25 feet) during a regular rainy season is not necessarily a good thing for the people living in haor region. For example, people catch fish in aus paddy field when the water level is approximately 4 to 6 feet; and a decrease of water level by 5.25 feet will leave those fields almost dry, depriving many from necessary protein and livelihood. Also, the farmers decompose jute plants under 4 to 5 feet of water, which will be hindered should the water level drops by 5.25 feet.
The report continues as follows, ‘Dry season flows will be increased substantially (for example, average flows of the Barak River at Amalshid would be 4.2 times larger in February and overall dry season flow volumes would increase by 60%). This would increase water levels by 1.7 m at Amalshid. Increases in dry season water levels would also occur on the Kushiyara and Surma Rivers (for example, water levels during March should increase by 1.5 m at Sherpur). These increased dry season flows will provide benefits for navigation, irrigation, and fisheries, but could also reduce drainage from some areas.’ Such an increase in water level will result in drainage congestion, causing problems for farmers. For example, the farmers in haor region prepare their boro field during January-February, when the fields need to be almost dry; and the maximum water depth needed during this time is only a few inches. Stagnation of water in the fields by few feet will mean a complete failure of the crop. From the above analysis, it can be concluded that only a natural flow in the Surma-Kushiyara-Kalini-Ghorautra-Meghna system can ensure the continuity of a long-term equilibrium that the people and ecosystems in watershed have been relying on. Any interference with the natural flow will result in uncertainty that will have negative impacts. Let the rivers flow freely.
Md Khalequzzaman is a professor of geology at Lock Haven University in Pennsylvania, USA. email@example.com.