What we need to know
According to UN convention, for any intervention on an international river, the upper riparian should supply all information about survey and data collection, design and report, activities in pre- during- and post-construction stages before starting the construction of a dam/barrage. Any disagreement or dispute should be resolved bi-laterally. Any gross disagreement with or violation by the upper riparian such as unilateral construction and withdrawal of waters may lead to reference with the UN. But all attempts must be made to resolve the issue between the parties sharing the common river basin.
A dispute on an international river may stretch for a long time. Farakka issue started in the sixties and an agreement was reached after about 40 years, in 1996. One can say that the problem is not over yet. It may take many more years to get fair share of water of the Ganges as agreed upon. As the agreed share of water is not reaching Bangladesh, we have been facing catastrophic situation in the SW region, severely affected by drought and desertification, environmental degradation and saline water intrusion from the sea as a result of very low or nearly absence of upland flow.
Similar situation may occur in Brahmaputra basin as a result of diversion of Brahmaputra water for river-linking project in India.
For the reported Chinese gargantuan plan of diversion of Brahmaputra waters for blooming the dry and barren Gobi desert, thousands of miles away, there may arise need for water conservation during the dry season. China is imposing a third dimension in the already volatile and critical water crisis.
We expect that similar deplorable situation may not arise in the Surma-Kushyara-Meghna basin in the near future due to Tipaimukh Dam. We must have assurance that water sharing agreement of Tipaimukh will not follow the one that obtains for Farakka which made SW region a dry land. Government may request India to stop the construction for better. However, the following data should be sought.
Tipaimukh Dam is a rockfilled dam. For any dam design, types and requirements of data are enormous. Only the relatively important ones are highlighted here:
Climatological data: Rainfall-Daily rainfall at damsite. Hourly rainfall data from automatic recorder. Data from an old station -- either a nearby city or airport -- on daily rainfall, hourly rainfall from auto recorder, evaporation, humidity, temperature, wind.
Hydrological data: Discharge from a long duration nearby station and from dam and barrage site stations, types of currentmeters (Price Ott or other), type of bed load samplers, method used in discharge measurement, launch and extant and hydrometric markers on weekly, fortnightly or monthly intervals.
In hourly discharge, particularly observed at dam site or from a nearby station, we may have to resort to use unit hydrographs and calculate probable maximum flow using rainfall data.
Water level -- From staff gauge daily mean water level, hourly WL from auto recorder.
Sediment data -- Bed load and suspended load.
Cross-sections -- Some cross sections at and up and down of dam site.
Water quality -- Important parameters to be made available.
Geology: Necessary geological information for areas around the dam and the reservoir in report, drawings and maps. Maps of Geological Survey is also required.
Topographic surveys, drawings and maps: Cross-sections of dam site, up and down at designed intervals. Maps of regular topographic surveys with contours, made by Survey of India are required for delineating reservoir area, height of dam, reservoir capacity, volume vs area and area vs height relationships etc.
Geotechnical investigations: Tests are conducted on collected samples, shear strength, compaction, compression and consolidation settlement, tri-axial tests for shear strength, load bearing capacity, stability analysis of slopes, permeability and seepage analysis etc.
Studies should also be made for sites used for materials for the dam, area and quantity of suitable materials. Seepage analysis will show seepage flow through the foundation so as to ascertain the stability of the dam against erosion and subsidence.
Geophysical investigations, electrical resistivity surveys: Geophysical surveys should be conducted on dam site, u/s and d/s in designed intervals. Survey should be conducted in the reservoir area. Longitudinal surveys of the dam site upto end of reservoir and d/s for the designed distance, location of faults, spots of leakage and any weakness of dam site itself. Major earthquakes magnitude (Richter scale), records of earthquakes etc since the area is frequented by earthquakes, situated in one of the most seismically active zones in India.
Some suggestions
Design of dam -- shape of the dam, drawings -- Reports of different analysis/studies, stress analysis, factor of safety etc, u/s and d/s slopes, impervious membrane, dry rubble below u/s slope and loose rockfill below d/s slope etc, seepage analysis through the dam and foundation to show its stability against subsidence, soil erosion at the d/s slope, seepage though the foundation -- all investigations and studies should be collated, and synchronised for design.
Dam, reservoir and storage: We must have copy or design of the dam and reservoir, particularly in respect of supply and demand of water like inflow of river and runoff from rainfall over the reservoir and loss, evaporation and seepage. Demand side would include requirements of water for hydropower, drinking water supply, ecological release, flood control storage and storage to compensate evaporation and seepage.
Dam break study: The total massive stored volume of water should be considered in dam break study to anticipate, predict the inevitable deluge which will lead to flooding in Surma, Kushiyara and Meghna basins, causing untold miseries, death and destruction. The reported designed volume of 15 billion m3 water will submerge the greater Sylhet district to a depth of 15 feet or more! This deluge occurs during catastrophic hydrological upheavals or devastating earthquakes. Invariably, dams and reservoirs with huge dead weight tend to accentuate the occurrence, frequency, intensity, magnitude and severity of earthquakes more so in the seismically active earthquake-prone zone.
Methods and instruments for data collection: Methods of observations and instruments used in climatologically, hydrological and other investigations and observations, should be asked for ascertaining the accuracy, appropriateness and veracity of data collected and used for design.
Environmental impact assessment study: It is to be ascertained whether the study apart from other impacts, included adverse effects on economy and environment in the lower riparian Bangladesh. Whether the damages were expressed in monetary figures and suggested mitigation measures. As upper riparian, is expected to bear the cost of mitigation activities involved, all studies, data used, assumptions made etc. should be made available to Bangladesh.
Shared water for Bangladesh: Ascertain whether the water released by turbine after generating hydroelectricity, will be allowed to flow downstream for Bangladesh, along with rate set aside for ecological flow and the balance of flow that is required to total the agreed equitable and fair rate of flow for Bangladesh.
Sedimentation and life of reservoir: Details of calculation of reservoir sedimentation should be supplied to Bangladesh to ascertain the life of the project.
Design of spillway: All calculations and drawings are needed to ascertain how the spillway bed level was fixed, how the maximum flow rate and its depth above the bed was determined.
Turbine flow: Turbines, type, size, capacity its rate of flow etc number and size (KVA) of generators and its generating capacity; information regarding discharge of turbine water after its use, whether it is discharged in river downstream to flow to Bangladesh or intercepted by a barrage -- details of all technical data should be provided.
Fulertal Barrage: Bangladesh delegate will ask for data and design of Fulertal barrage. If there is irrigation, ask for area under irrigation, crop type, total water used per season/yearly in million/billion m3 and other data.
Concluding remarks
The expected uninterrupted flow released from turbines of the dam is supposed to be halted for diversion at the Fulertal barrage, situated about 100 km downstream of the dam and 100km from Bangladesh border. In that case there is an immediate and urgent need to negotiate and settle our equitable and fair share of Barak waters. Our government may request India to stop the construction of both the dam and barrage as none of them, in any way, is helpful for Bangladesh. There is strong apprehension that near desertification conditions of SW region as a result of Ganges water withdrawal at Farakka will be replicated in NE region, in more than 50% of land area of the country which will be fearfully affected.
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