Seasonal Behaviour of a Shallow Estuary of Lower Cauvery Basin, India (original) (raw)
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Environmental Earth Sciences
The Kochi Backwater (KB) is the second largest wetland system in India. It is connected to the sea at Fort Kochi and Munambam (Pallipuram) (30 km north of Kochi). As the tide is forced through two openings, its propagation in the backwater system is very complicated, particularly in the northern arm of the estuary. Using synchronous water level (WL) and current measurements in the KB from a network of stations during 2007–2008, it was convenient to demarcate the northern KB into two distinct regions according to the tidal forcing from the north (Pallipuram) and south (Vallarpadam). This demarcation is useful for computing the propagation speeds of the dominant tidal constituents in the northern branch of the KB with dual opening for opposing tides. WL variations indicated that M2 tide (Principal lunar semidiurnal constituent) dominated in the sea level variance, followed by the K1 constituent (Luni-solar declinational diurnal constituent). The M2 tidal influence was the strongest near the mouth and decayed in the upstream direction. The propagation speed of the M2 tide in the southern estuary was ~3.14 m/s. The ratio of the total annual runoff to the estuarine volume is ~42 that indicates the estuary will be flushed 42 times in a year. KB can be classified as a monsoonal estuary where the river discharge exhibits large seasonal variation.
River mouth dynamics of Swarnamukhi estuary, Nellore coast, southeast coast of India
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… . Earth Syst. Sci, 2013
The intratidal, spring-neap and seasonal variations in stratification were examined in the Cochin estuary. The observations established a strong connection with the distribution of chemical and biological properties. The influence of tides and river discharge forcing in water column stability was quantified using potential energy anomaly (PEA) and stratification parameter. Partially mixed (neap) and wellmixed (spring) conditions during low river discharge (dry) period were altered in monsoon by the salt wedge intrusions. The ecological impact of salt wedge propagation on high tides bringing upwelled water to the system was evident from the bottom hypoxic, high chlorophyll a and nutrientrich conditions. Phosphate and nitrite concentrations were higher at the bottom saline conditions but silicate and nitrate were clearly supplied by river water. However, during ebb tide this front was driven out of the estuary. The periodic advance and retreat of the salt wedge was inevitable in making the system immune from extended hypoxia/anoxia and maintaining the health of the Cochin estuary. For the seasonally varying river flow in the estuary, salt intrusion receded with increasing river flow in monsoon and rebounded with decreasing river flow in dry season. During monsoon, the intense flushing and reduction in salinity field expansion seemed to be responsible for the limited chlorophyll a levels along the surface of the Cochin estuary.
A study was undertaken during May 2017 to monitor the impact of tidal actions on the hydrological parameters of the Hooghly estuary. The water quality reflects the impact of Bay of Bengal (sea) water almost on all the variables as revealed from the significant difference of parameter values in high and low tides (except surface water temperature and K). The 12 selected stations from the upstream to downstream regions exhibited uniformity with respect to surface water temperature. Significant spatial variations (at 5% level of significance) were observed with respect to parameters like surface water salinity, pH, alkalinity, DO, BOD, COD, NO3, PO4, SiO3, extinction coefficient, SO4, Na, K, Cl and total N. Along with tidal influences, the anthropogenic factors contributed by the adjacent cities and towns exert a regulatory influence on parameters like BOD, COD, NO3, PO4, extinction coefficient, SO4 and total N.
Salinity and suspended sediment transport in a shallow estuary on the east coast of India
Regional Studies in Marine Science, 2016
h i g h l i g h t s • Pronounced seasonal variations in the transport of salt and suspended sediments were observed in the Muthupet estuary. • The salt moved in the upstream and downstream direction from the salt plug. • Salt transport affected the movement and removal of Fe from the water column. • Concentration of Cu and Cd was affected by resuspension of sediments. • The cause of more transport of suspended sediments was due to lower settling velocity of suspended sediments.
Seasonal variation of oceanographic processes in Indus river estuary
MAUSAM
Field investigations were conducted to study spatial and temporal (seasonal) variations in meteorological, hydrodynamic and hydrological variables in Indus River Estuary. The investigations were undertaken during wet, (moderate fluvial discharge), flood (highest fluvial discharge) and dry (zero fluvial discharge) seasons to obtain surface and near bed data during flood and ebb tides. Tides were semidiurnal, showing an asymmetric pattern with longer ebb tides and shorter flood tides. The hydrodynamic data revealed strong seasonal variation, the ebb velocities were significantly higher than flood current velocities during wet season, whereas a slight difference was found in current velocities during dry season, while the ebb phase lasted longer than flood during wet season; however no significant difference was observed during dry season. On the other hand during flood period the water currents were substantially higher and unidirectional related to the strong river flow. Turbidity va...
Environmental Monitoring and Assessment, 2015
Determining robust values for estuarine material fluxes has been a complex task and an interdisciplinary research challenge. With the advent of Acoustic Doppler Profilers (ADPs) having bottom-track capability and which provides three-dimensional current velocity profiles, more accurate estimation of cross sectional fluxes is far accomplished in unsteady and bi-directional flow conditions of estuaries. This paper reports for the first time the discharge measurements conducted across Cochin inlet using ADP to examine the spring-neap variability in residual fluxes of water and nutrients during dry season. Cross sectional current velocity profiles and salinity profiles were captured using ADP and CTD. Samples of surface and bottom water were also collected at three hour intervals. The results indicated that there is a distinct transition from the neap to spring tides related to flow and salinity structure. The neap tide was partially mixed with large diurnal inequalities whereas the spring tide was well-mixed with symmetric tides. During ebb, an increase in the concentrations of nitrate, nitrite, phosphate and silicate was noticed indicating upstream sources for their inputs. In contrast, elevated levels of ammonia were found in the estuary throughout the period of observation. There was net residual outflow during both tides and the computed residual water fluxes of neap doubled that of spring. The strong ebb currents and the increased nutrient concentrations during ebb resulted in the export of all nutrients (except ammonia during spring) into the sea. The findings of this study highlight the consequences of anthropogenic interventions in the estuary and their effects on the fluxes of ecologically relevant substances.
Modeling of tidal circulation and sediment transport near tropical estuary, east coast of India
Regional Studies in Marine Science, 2020
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Tapi river is one of the perennial rivers in the west coast of India and its end with Arabian sea near surat city. The aim of the study is to investigate the spatial, seasonal and tidal variation of selected water quality parameters of the estuary. The samples have been collected in three different seasons Postmonsoon (January 2015), Premonsoon (April 2015) and Monsoon (August 2015) at 9 selected sites during low and high tide. The various nutrients and physicochemical parameter measured by in-situ measurement and laboratory analysis method. The different physicochemical parameters such as Water temperature, Salinity, Dissolved oxygen, Phosphate, Nitrate, Nitrite, Ammonia, Total nitrogen and pH varied from 24.20 to 29.30 °C, 0.1 to 25.8 ppt, 1.3 to 6.9 mg/l, 15.32 to 72.50 μg/l, 115.94 to 292.60 μg/l, 20.86 to 182.40 μg/l, 11.21 to 54.10 μg/l, 372.00 to 780.45 μg/l and 7.2 to 8.2 respectively. The result shows that the DO and nutrient concentration, except nitrate and ammonia, is the highest during the monsoon season, whereas Salinity, pH and Biological oxygen demand are the highest during the pre-monsoon period and the lowest during the monsoon period. The statistical tools package used SPSS.20 to anlyse the correlation between parameters at different seasons. Analysis of variance test results showed Water temperature, salinity, Dissolved oxygen, Nitrite, Total nitrogen and pH showing significant (p<0.05) variation and Biological oxygen demand, Phosphate, Nitrate and Ammonia showing non-significant (p>0.05) variation seasonally. The tidally, Dissolved oxygen and pH are non-significant (p>0.05) and all parameters are significant (p<0.05). The results revealed that Tapi estuary water quality has been affected by anthropogenic effect, agriculture and land runoff and industrial effluent discharge to estuary.
Studies on Decadal Variability in Dilution and Flushing Characteristics of Cochin Estuary
CERTIFICATE This is to certify that this dissertation entitled "STUDIES ON DECADAL VARIABILITY IN DILUTION AND FLUSHING CHARACTERISTICS OF COCHIN ESTUARY" is a bonafide record of the project based on the work carried out under our supervision by Mr. 2 DECLARATION I, Dharampal M S hereby declare that the dissertation, entitled " STUDIES ON DECADAL VARIABILITY IN DILUTION AND FLUSHING CHARACTERISTICS OF COCHIN ESTUARY " submitted to the Kerala University of Fisheries and Ocean Studies in partial fulfilment of the requirements for the award of degree of Master of Science in Physical Oceanography and Ocean modeling is a record of original project work done by me during