Setting up a simplified salt intrusion model with data from a hydrological network

ABSTRACT

Salt intrusion modelling for an estuary typically requires topography data, including cross-sectional area and width along the estuary. This information is typically collected by field trip measurements, but these are not always feasible. Furthermore, freshwater discharge data are needed but these are generally gauged further upstream outside the tidal region and unable to reflect the individual flows entering a multi-channel estuary. With data provided by a network of fixed measurement stations only, the main goal of this paper is to set up an analytic model to simulate salinity distribution along a multi-channel estuary at high water slack. The Ma Estuary in Vietnam is considered as case study. A new approach is introduced to calibrate the parameters of a parsimonious salt intrusion model, which are typically extracted from estuary geometry measurements. Compared to the values derived from a field survey, the calibrated parameter values are in very high agreement. Furthermore, by assuming a linear relation between inverses of the individual flows entering the estuary and inverses of the sum of flows gauged further upstream, the individual flows can be assessed. Evaluation on the model simulations shows that the model explains salinity distribution along the Ma Estuary reasonably well with 75% of the simulations being satisfactory or better and with NSE values at the gauging stations being 0.50 or higher. This performance demonstrates the predictive power of the model and of the proposed parameter/input estimation approach.

KEYWORDS:

• Salt intrusion
• estuary
• conceptual model
• network of fixed measurement stations
• water quality modelling

Acknowledgements

We would like to convey our thanks to Geert Delattin and Klaas Verhoeve for their kind help. We also appreciate two reviewers for their critical comments that are very helpful to improve the manuscript. The hydro-meteorological centre of Thanh Hoa Province are gratefully acknowledged for providing the salinity and flow measurement data in the Ma catchment. This research was conducted as a part of the ICP PhD project ‘Simulation of saline water intrusion into downstream of the Ma River catchment taking into account the impact of climate change in dry season’, sponsored by VLIR-UOS.

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Duc Anh Nguyen http://orcid.org/0000-0002-2157-4092

Thuy Nguyen Thanh http://orcid.org/0000-0003-0546-6603

Patrick Willems http://orcid.org/0000-0002-7085-2570

Jaak Monbaliu http://orcid.org/0000-0002-6107-4201

Additional information

Funding

This work was supported by Vlaamse Interuniversitaire Raad [grant number ICP Ph.D. 2012 - 002.