Water Shortage in the Gorai river Basin and Damage of Mangrove Wetland Ecosystems in Sundarbans, Bangladesh (original) (raw)
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The Sundarbans is situated in the Ganges transboundary catchment which is known as the single largest mangrove ecosystems in the world and covers 10,000 km² between Bangladesh and India. Since the diversion of Ganges water at Farakka Barrage in India from early 1975, salinity level has increased drastically in the south western part of Bangladesh. Due to reduction of fresh water flow urban drinking water supply, industrial production, agriculture, fisheries, navigation, hydromorphology and mangrove wetlands ecosystems have been affected. Urban area both surface and groundwater have become unfit for human consumption. In the consequences about 0.170 million hectares (20.4%) of new land, and almost 27 small towns have been affected by various degrees of salinity during the last three decades. The saline front defined by 6 dS/m iso-haline has penetrated up to 173 km north from the coast. The salinity has exceeded the recommended level 1 dS/m for potable water. It is a new threat to supply quality drinking water to the small towns in the south western region in Bangladesh. The dominant mangrove Heritiera fomes and Ceriops decendra species are affected by top dying disease which is recognised as key management concern. The Fourier Polynomial water salinity models on Sundarbans rivers are showing the cycling increasing behaviour. The findings of this study a potential contribution for making comprehensive management plan are for urban water supply, and protection of the mangrove wetlands ecosystems in the Sundarbans region.
Mangrove wetland ecosystems in Ganges-Brahmaputra delta in Bangladesh
Frontiers of Earth Science in China, 2008
The Sundarbans is one of the productive mangrove wetland ecosystems in the Ganges-Brahmaputra delta in Bangladesh. The delta is undergoing rapid ecological changes due to human activity. In the present study, surface water salinity data from 13 rivers of the Sundarbans were collected in order to investigate the saline water intrusion in the mangrove wetlands. Results demonstrate that saline water has penetrated the upstream area as river water salinity has increased significantly in 1976 compared to the year 1968. The soil and river water salinity data also shows that it has crossed the water salinity threshold line in most parts of the Sundarbans wetlands. These observations are due to the construction of Farakka Barrage in 1975, which reduced the water discharge of the Ganges River from 3700 m 3 /s in 1962 to 364 m 3 /s in 2006. The shortage of freshwater discharge to the deltaic area is trailing active ecosystems function, especially in the dry season in the south western region in Bangladesh. The objective of this study is to understand and analyze the present degraded mangrove wetland ecosystems and their negative impacts. The findings of this study would contribute to the formulation of the mangrove wetland ecosystems management plan in the Ganges delta of Bangladesh.
Hydrologic monitoring and analysis in the Sundarbans mangrove ecosystem, Bangladesh
Journal of Hydrology, 2007
The unique habitat of the Sundarbans mangrove ecosystem is dependent upon the hydrological regime. Therefore, a comprehensive study to understand the hydrologic behaviour and the changes that have taken place due to anthropogenic activities in and around the area is fundamental to the management of natural resources and environment. In the past, ad hoc and uncoordinated efforts were made due to the inherent inaccessibility and high cost of data collection. The present article documents the results of the hydrologic monitoring, modelling and analysis in the Sundarbans. The study results show that the annual maximum tidal range has increased by about 0.75 m in the eastern and central parts during the last two decades. About 60% area remains in higher salinity condition (>20 ppt) for at least 1.5 months in a year. Organic pollution in the waterways is within the Environmental Quality Standard (EQS) of Bangladesh with the average Dissolved Oxygen (DO) of 5.99 mg/L. Total Ammonia, Nitrate (NO 3-N) and Phosphate (PO 4-P) level are present in sufficient quantity for the aquatic life to survive and are within EQS limit. Lead and Chromium occasionally exceed EQS limit especially along the large barge routes in the western part. The data and information presented in the paper will serve as a baseline for future hydrological and environmental studies.
International Journal of Advanced Geosciences
Long term variation in upstream water flow through the Ganges−Gorai river are affecting the salinity levels of south-western coastal region of Bangladesh. Salinity data for the Rupsha river was collected for several years to demonstrate the historical changes of salinity level in the south-western coastal region. Furthermore, discharge data of the Ganges and Gorai river were also collected to discuss the effect of upstream discharge on the variation of salinity level. This study also collected water and soil samples from different places of this region to measure the salinity level and compare the values with the standard ones. A decreasing trend in dry season Ganges-Gorai river flow was observed after the initiation of the Farakka barrage in 1975. Consequently, the south-western region underwent high salinity level. The Ganges sharing treaty in 1996 and dredging of the Gorai riverbed (GRRP-I and GRRP-II) in 1999 and in 2012 helped the region to recover from high salinity level for ...
Hydrological changes in the Ganges system in Bangladesh in the post-Farakka period
Hydrological Sciences Journal, 1997
The basin area of the Ganges River in Bangladesh is extremely dependent on a regular water supply from upstream to meet requirements for agriculture, fisheries, navigation, salinity control, and domestic and industrial sectors. In 1975, India commissioned a barrage on the Ganges River at Farakka to divert a significant portion of the dry season flow in order to make the Calcutta Port navigable. Statistical analyses of discharge and water level data have been carried out to determine if significant changes have occurred in the hydrology of the Ganges system in Bangladesh in the post-Farakka period. Siltation of the Gorai River (an offtake of the Ganges River) has also been examined using the stage-discharge relationship and regression analysis. The analyses show that the diversion has caused considerable hydrological changes in the Ganges system in Bangladesh. The water supply in the dry season has been reduced substantially, while siltation of the Gorai River has increased significantly. Modifications hydrologiques du système du Gange au Bangladesh depuis la construction du barrage de Farakka Résumé Un approvisionnement en eau régulier venant de l'amont est d'une extrême importance pour la région du bassin du Gange au Bangladesh en vue de satisfaire les besoins de l'agriculture, des pêcheries, de la navigation, du contrôle de la salinité, aussi bien que pour les secteurs domestique et industriel. L'Inde a construit, en 1975, un barrage sur le Gange à Farakka pour détourner une importante partie de l'écoulement de saison sèche afin de rendre navigable le port de Calcutta. Une analyse statistique des débits et des niveaux d'eau a été réalisée pour rechercher si l'hydrologie du système du Gange au Bangladesh a subi des modifications significatives depuis la mise en service du barrage de Farakka. L'ensablement du fleuve Gorai (un bras dérivé du Gange) a également été étudié à travers la relation entre niveau et débit et une analyse de régression. Ces analyses montrent que la dérivation est à l'origine d'importantes modifications hydrologiques dans le système du Gange au Bangladesh. La quantité d'eau disponible pendant la saison sèche a été substantiellement réduite alors que l'ensablement du fleuve Gorai s'est significativement accru.
Water Salinity Investigation in the Sundarbans Rivers in Bangladesh
Bangladesh, through its complex network of river systems, drains an area of about 1.76 million km 2 of the catchments of the Ganges, the Brahmaputra and the Meghna, of which only 7.5% lies in Bangladesh. The Sundarbans is situated in the Ganges catchment area, which is known as the single largest mangrove forest and unique ecosystem in the world. It has an area 6017 km 2 and a natural shield that protects the coastal area from storm surges and cyclones. It also plays a potential role in the regional economy and ecosystems. Since the diversion of Ganges water at Farakka Barrage in India from early 1975, as a result the water and soil salinity has penetrated. Consequently, both siltation and increased salinity have degraded water quality in the Sundarbans rivers, and threats for mangrove ecosystems. At present, ground water use in the study area is less because of high salinity intrusion. For salinity investigation, time series data for four years (13 rivers) were used for water salinity modelling. The objectives of this paper are to investigate the water salinity approximation in the Sundarbans rivers, which will be considered as a tool for decision making. It will make a contribution to develop an interdisciplinary management plan and to ensure that fresh water is supplied to the Sundarbans by the Ganges for the protection of mangrove ecosystems.
Bangladesh through its complex network of river systems drains an area of about 1.76 million sq. km ofthe catchment ofthe Ganges, the Brahmaputra and the Meghna of which only 7.5 percent lies in Bangladesh. The Sundarbans is situated in the Ganges catchment area which known as the single largest stretch ofproductive mangrove forest and unique ecosystems in the world. It is reprcsenting 3.5 percent of the world mangrove and consisting of an area 6017 sq. km. It provides direct employment opportunity to 600,000 people and 6 million people indirectly dependent. Since the diveßion of Ganges water at Farakka Barrage in India from early 1975, salinity levels have increased drastically in the coastal region in Bangladesh. The reduction ofGanges flows while the industries are facing serious problems in quality control of products and disastrous effects on agriculture, fisheries, navigation, hydro-morphology, drinking water, wetlands and mangrove ecosystems. The dominant flefi/iera fomes ard Ceriops decandra species are affected by top-dying disease which is recognised as key management concern. The Ganges water shadng is not just a geo-techno-political problem it is also a humanitarian problem. The objectives of this paper is to contribute to formulate a long-term management plan for mangrove wetlands resources through ensure to supply Ganges water into Sundarbans. GIS simulation and salinity model would be the proper tools for decision making and make recommendations for the future of Ganges water sharing conflict and protection of Sundarbans wetlands ecosystems.
The Ganges and Brahmaputra rivers in Bangladesh: basin denudation and sedimentation
Hydrological Processes, 1999
Every year the Ganges and Brahmaputra rivers in Bangladesh transport 316 and 721 million tonnes of sediment, respectively. These high loads of suspended sediment re¯ect the very high rate of denudation in their drainage basins. The average mechanical denudation rate for the Ganges and Brahmaputra basins together is 365 mm 10 3 yr À1 . However, the rate is higher in the Brahmaputra Basin than that in the Ganges Basin. Several factors, including mean trunk channel gradient, relief ratio, runo, basin lithology and recurring earthquakes are responsible for these high denudation rates. Of the total suspended sediment load (i.e. 1037 million tonnes) transported by these rivers, only 525 million tonnes (c. 51% of the total load) are delivered to the coastal area of Bangladesh and the remaining 512 million tonnes are deposited within the lower basin, osetting the subsidence. Of the deposited load, about 289 million tonnes (about 28% of the total load) are deposited on thē oodplains of these rivers. The remaining 223 million tonnes (about 21% of the total load) are deposited within the river channels, resulting in aggradation of the channel bed at an average rate of about 3 . 9 cm yr À1 . Although the Brahmaputra transports a higher sediment load than the Ganges, the channel bed aggradation rate is much higher for the Ganges. This study also documents a wide range of interannual, seasonal and daily variation in suspended sediment transport and water discharge. Interannual variation in sediment deposition within the basin is also suggested.