Salinity modelling for the Sabine?Neches Estuary, Southeast Texas

Abstract

A two-dimensional, depth averaged, computer code was used to model salinities for the Sabine–Neches Estuary in Southeast Texas, USA. The model bathymetry was set to the mean sea level of 1996, and channel friction was adjusted to give an optimised Manning's n value for the annual, 6-minute water level data at eight stations.The simulated velocities were checked using flow discharges measured at six estuary sections for a three-day survey period. Three dispersion methods were used to calibrate the model for salinity. The data used were a 6 month record for 1996 at seven estuary stations, and a 7-year partial record from 1990 to 1996 for two stations at the Upper and Lower ends of Sabine Lake. The first method used a constant salinity dispersion coefficient and the second used a velocity related coefficient; they were accurate to within an annual mean value of about 5 ppt. For the third method, a two dimensional dispersion function was derived, which modelled to within an annual mean value of about 1 ppt. The ultimate purpose for the study was to estimate salinity increase for Sabine Lake with designed, fresh water flow extractions from the catchment. A maximum salinity increase of about 2 ppt for a 50 year return period was estimated.