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

Abstract

ABSTRACTSalt 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.