Article Author Version of : Water, vol.12(3); 2020; Article no: 908 What controls the flushing efficiency and particle transport pathways in a tropical estuary? Cochin estuary, southwest coast of India Sebin John1, 2, Muraleedharan K.R1*, C.Revichandran1, Abdul Azeez.S1, Seena G1, 2, Pierre W Cazenave3 1 CSIR‐National Institute of Oceanography, Regional Center,Kochi 2 Research Scholar, Bharathidasan University, Tiruchirappalli 3 Plymouth Marine Laboratory, UK * Correspondence:
[email protected] Received: date; Accepted: date; Published: date Abstract: Estuaries with poor flushing and longer residence time retain the effluents and pollutants, ultimately resulting in eutrophication, declining in biodiversity and, finally deterioration of water quality.Cochin Estuary (CE), southwest coast of India is under the threat of nutrient enrichment by the anthropogenic interventions and terrestrial inputs through the land runoff. The present study used the FVCOM hydrodynamic model coupled with a Lagrangian particle module (passive) to estimate the residence time and to delineate site‐specific transport pathways in the CE. Moreover, understanding the back and forth movements and residence time of particles was elucidated using metrics such as path length, net displacement, tortuosity and time to flushed out from the system. Spatio‐temporal patterns of the particle distribution in the CE showed a similar trend during monsoon and post‐monsoon with an average residence time of 25 and 30 days respectively. During the low river discharge period(pre‐monsoon),flood‐ebb velocities resulteda minimum net transport of the water andlonger residence time of 90 days compared to that of high discharge period (monsoon). During the pre‐monsoon, particle releasedat the southern upstream (station.