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Seasonal and Tidal Influence on Surface Water Quality – A Case Study in the Hau River Segment, Vietnamese Mekong Delta Province

Ni Duong Van, Viet Le Hoang, Ly Nguyen Hong Thao

Journal of Ecological Engineering

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2022

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Vol. 23, nr 8

290--298

EN

The study aimed to evaluate the influence of seasons and tides on surface water quality of Hau River in Hau Giang province, Vietnam. The water quality data were collected at six locations at low tide and high tide. The monitoring parameters included pH, dissolved oxygen (DO), biochemical oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), ammonium (NH4+-N), nitrate (NO3--N), orthophosphate (PO43--P), total phosphorus (TP), total nitrogen (TN), iron (Fe) and Coliform. One-way analysis of variance (One-way ANOVA), cluster analysis (CA) and discriminant analysis (DA) were applied to determine the influence of tides and seasons on water quality. The surface water quality was compared with the national technical regulation on surface water quality in column A1 (QCVN 08-MT:2015/BTNMT). The results showed that surface water in the study area had organic pollution and high eutrophication potential. The BOD, COD, TN, TP, Fe and coliform parameters in low tide tended to be higher than those in high tide. Five parameters, including TSS, TP, TN, PO43--P and coliform had a significant difference between the wet season and the dry season by DA analysis. Cluster analysis classified the water quality into three clusters, mainly by the BOD, COD, TSS, PO43--P and Fe parameters. The study provides important information on the water quality of the Hau River in the Hau Giang province for water uses and monitoring.

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A comparison between the suspended sediment concentrations derived from DELFT3D model and collected using transmissometer – a case study in tidally dominated area of Dithmarschen Bight

Rahbani M.

Oceanologia

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2015

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No. 57 (1)

44--49

EN

The objective of this investigation is to verify the deficiencies that incorporate both modelled and measured suspended sediment concentrations (SSC) data in a tidal dominated area. For this purpose a tidal channel, in the North Sea, was considered as the case study. The profiles of SSC from a model were compared with those from the field, in which some dissimilarity was observed. Intensive investigations were carried out to detect that the most discrepancies occur in shallow parts of the area and also during the low velocities. The origin of the shortcomings in regard with the modelling and measuring technique are discussed.

3

Evaluation of uniform current dynamic effect in practical ship manoeuvring

Artyszuk J.

Annual of Navigation

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2004

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No. 8

57-66

EN

The dynamic model of the uniform current, as introduced in the previous paper of this volume, is assessed against a bit simpler approach called semi-dynamic one. In the latter, a ship is assumed to move in still water and the over ground movement is just computed after each iteration of the differential equations integration. The level of inaccuracy caused by the semi-dynamic method depends upon the manoeuvre type. Also, some aspects of ship berthing in the ahead uniform current are raised, and compared with different degrees of simplification as employed in the shiphandling practise while dealing with the current (referred to in general as the kinematic model).

4

A uniform current in ship manoeuvring mathematical model

Artyszuk J.

Annual of Navigation

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2004

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No. 8

67-76

EN

Some essential aspects of mathematical modelling the uniform current dynamic impact on ship manoeuvring are discussed and assessed. a simulation of a pure drift, and such a drift coupled with a turning motion is next performed for a small tanker. The one-knot current gives rise to the maximum yaw velocity of order fifteen degrees per minute associated however with a relatively long response time.