Water, Salt and Nutrient Flux Through the Lower Meghna River Estuary, Bangladesh

1 Water, Salt and Nutrient Flux through the lower Meghna River estuary, Bangladesh N MAHMOOD 1 , S R CHOWDHURY 2 , A S M SHARIF 3 , M M UDDIN 3 AND M S ULLAH 3 1 Professor, 2 Assistant Professor, 3 Research Associate Institute of Marine Sciences, University of Chittagong, Chittagong-4331, Bangladesh E-mail: [email protected] Keywords: Nutrient flux, Meghna estuary, Bangladesh Abstract Water, Nutrient and Salt transport through the lower Meghna estuary, a combined flow of the Ganges and Brahmaputra and many other rivers, was studied. Despite a very complex network of rivers and channels, a simple approach of measuring these parameters for an annual cycle during premonsoon, monsoon and postmonsoon seasons covering an area of about 532 km 2 results in knowledge in this previously untouched arena of material flux. Althoug h, v astness and complexity of th e estuary made it almost impossible to sample each and every creek and channel, an attempt was made to fit a single layer simple box model to study the budget of these materials in the lower reaches of the river estuary. Study area description The Meghna River is the main outlet of the Ganges-Brahmaputra river system collecting water from a vast catchment area of India, Bangladesh and Nepal. At the lower reaches of the river system the Meghna River is connected to numerous smaller rivers, channels and creeks before emptying into the Bay of Bengal to the southern middle part of Bangladesh. At the lower reaches, the river forms a huge estuary during the premonsoon seaso n and turn s almost fresh during the monsoon and early postmonsoon. This paper presents the budgets of water, salt and nutrients for the Lower Meghna River estuary using the LOICZ Biogeochemical Modelling Guidelines (Gordon et al, 1996). For the water, salt and nutrient budgeting an area of approximately 532 km 2 between about 22°25'N, 90°40'E and 22°40'N, 91°05'E has been selected in the lower Meghna River (Figure 1). Average depth of the estuary is 5-6 m. Water level rises by about 1 m during the Monsoon from that of the premonsoon (Chowdhury, 1993). Figure 1: Map showing the budget site - lower Meghna River estuary BAY OF BENGAL Lower Meghna River estuary 23° N 22° N 91°E 0 k m 20 In: Assessment of material fluxes to the coastal zone in South Asia and their impacts, APN/SASCOM/LOICZ Workshop 8-11 December 2002, Negombo, Sri Lanka

Water, Salt and Nutrient Flux Through the Lower Meghna River Estuary, Bangladesh

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