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Biogeochemical budgets for Tapi Estuary

DRS at CSIR-National Institute of Oceanography

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Title Biogeochemical budgets for Tapi Estuary
 
Creator Bapardekar, M.V.
DeSousa, S.N.
Zingde, M.D.
 
Subject biogeochemical cycle
estuaries
tidal currents
salt budget
water budget
nutrients (mineral)
dry season
coastal zone
 
Description The Tapi estuary (21 degrees 10'N, 72 degrees 40'E) is a tidal estuary originating in the Multai Ghats in Madhya Pradesh at an elevation of 752 m. The 720 km long river, after passing through the 3 states of Madhya Pradesh, Maharashtra and Gujarat, discharges into the Gulf of Kambhat (Cambay), near Hazira. The average annual river runoff is 7,686 x 10 sup(6) m sup(3). The average rainfall in the area varies from 100 cm.y sup(-1) in the coastal plains to 150 cm.y sup(-1) in the ghat sections, 85% of which occurring during the southwest monsoon. Evaporation over the area is about 6 mm.d sup(-1). The average annual ground water flow into the estuary is estimated at around 18,000 x 10 sup(6) m sup(3).y sup(-1) while another 4,026 x 10 sup(6) m sup(3) y sup(-1) comes from the wastes. Chemical fertilizers are used in the basin at the rate of 113 kg.ha sup(-1). During the dry season the salinity in the estuary decreases progressively in the upstream direction form an average 32.53 psu at the mouth to 0.1 psu within a distance of 35-40 km. In the present study, the data used for budgeting purpose was collected during November-December, 1983 and May, 1984, covering the entire dry season. We have no data for the monsoon season. However, due to the heavy runoff during this season, the rate of water exchange is expected to be very rapid which would render the computation of non-conservative fluxes unrealiable. Consequently, the present work is restricted to the dry season only. LOICZ Biogeochemical Guidelines were followed to calculate the biogeochemical budges for water, salt and nutrients (DIN and DIP) utilizing the above data. For this purpose, the estuary was split into two boxes based on the salinity gradient. The outer box had an average salinity of 16.75 psu while the average salinity in the inner box was 2.37 psu. The study indicates that during the dry season the estuary loses water at the rate of about 13.42 x 10 sup(6) m sup(3) d sup(-1) in the form of residual flux at the estuary-sea interface. This results in export of salt at the rate of 330.13 x 10 sup(6) psu m sup(3).d sup(-1). Exchange between the estuarine water and the adjoining seawater replaces this salt loss. The water exchange time for the system as a whole was 4.87 d during the dry season. The system showed net removal of DIP and DIN at the rate of 13.40 mmol.m sup(-2) d sup(-1) and 108.9 mmol. m sup(-2) d sup(-1) respectively, serving as a sink for both DIP and DIN. Primary production in the system is assumed to be dominated by plankton, with a C:N:P ratio (C:N:P)part. of about 106:16:1 and the calculations showed the system as a whole to be net autotrophic and N-fixing
 
Date 2008-07-02T06:59:33Z
2008-07-02T06:59:33Z
2004
 
Type Book Chapter
 
Identifier An assessment of nutrient, sediment and carbon fluxes to the coastal zone in south Asia and their relationship to human activities. Final report for APN Project - Ref. Nos.: 2001-20 and 2002-05 (April 2001-February 2004) submitted to APN, 153-161p.
http://drs.nio.org/drs/handle/2264/1163
 
Language en
 
Rights Copyright [2004]. It is tried to respect the rights of the copyright holders to the best of the knowledge. If it is brought to our notice that the rights are violated then the item would be withdrawn.
 
Publisher IGBP