A power-law multivariable regression equation for salt intrusion length in the Bouregreg estuary, Morocco

Abstract

Prediction of salt intrusion length in estuaries is a challenge for managers as well as scientists in this field. Several numerical and empirical models have been developed for the prediction of salt intrusion length in recent decades. However, all these models require large data set on estuary geometry, tide, stratification turbulence which demands experimental cost and time, and which is not always available as in our case. Thus, for reducing the complexity of analysis, a new simple equation was derived to predict the salinity intrusion length using nonlinear multivariable regression in the Bouregreg estuary, Morocco. The equation relates salt intrusion length with freshwater discharge and tidal range using a power law. The salt intrusion length predicted by the developed equation was in good agreement (R² = 0.72) with that obtained using a numerical salinity transport model (HEC-RAS software “Hydrologic Engineering Center River Analysis System”). This simple formula is completely transparent and practical for Bouregreg estuary, allowing direct assessment of the parameters on the salt intrusion. Therefore, the proposed model can either be used to predict the salt intrusion for a given freshwater discharge and tidal range, or can used as a tool to design the minimum daily discharge to regulate the salt intrusion into the estuary, thereby providing assistance for management plans.

Keywords:

• Bouregreg estuary
• salt-intrusion length
• nonlinear multiple regression
• numerical model (HEC-RAS)

Code availability

HEC-RAS-1D is freely available under the terms of the GNU Lesser General Public License (http://www.hec.usace.army.mil/software/hec-ras/).

Disclosure statement

No potential conflict of interest was reported by the author.