On the Understanding of the Hydrodynamics and the Causes of Saltwater Intrusion on Lagoon Tidal Springs

Roger Pacheco-Castro,Cesar Canul-Macario,Paulo Salles,Alejandro Paladio-Hernandez

doi:10.3390/w13233431

Abstract

Springs are common features on the Yucatán coast. They can discharge either under the sea (submarine) or inland in coastal lagoons and wetlands. Previous observations of a coastal lagoon located on the northern Yucatán Peninsula (La Carbonera) reported sea water intrusion on a spring that discharge on a coastal lagoon (lagoon tidal spring). The saltwater intrusion occurs when the tide is at its lower level, which is the opposite to what has been reported for submarine springs in the Yucatán Peninsula. In this study, the hydrodynamics of the spring is analyzed and the driving forces controlling the seawater intrusion are identified and discussed. Time series of water levels, salinity, and velocity measurements in the lagoon, the aquifer, and the spring are analyzed by means of tide component decomposition and cross-correlations analysis of the tide signals. Results show that the main driving forces causing the intrusion are the density differences and pressure head gradients, and the mechanisms influencing the driving forces driving those differences are the tides, the friction in the lagoon, and the confinement of the aquifer; other mechanisms are discussed to present a complete idea of the complexity of the interactions between the coastal aquifer, the coastal lagoons, and the sea.

Highlights

In the state of Yucatán, México, submerged springs are common features that are located either on the sea or inland on coastal lagoons and wetlands
This paper studies the lagoon spring hydrodynamics, compares it to submarine springs, and analyzes the factors that cause saltwater intrusion through the spring
Measurements of water levels, salinity, temperature, and flow velocity confirm the occurrence of saltwater intrusion events from the lagoon to the underlying confined aquifer through the spring

Summary

Introduction

In the state of Yucatán, México, submerged springs are common features that are located either on the sea (submarine) or inland on coastal lagoons and wetlands. One important factor that controls the discharge is the tide, and during spring high tides, the flow may reverse, causing salt water to intrude the spring. Recent studies in coastal lagoons have reported an opposite behavior in lagoon springs [1,2] in which the flow reversal occurs during spring low tide, which is a behavior that is apparently counterintuitive; see below. This paper studies the lagoon spring hydrodynamics, compares it to submarine springs, and analyzes the factors that cause saltwater intrusion through the spring. Springs are points of groundwater discharge on the land or surface water bodies, and they are important features of aquifer systems, in karst aquifers [1,2,3]. In the case of karst springs, it has been proved that they can provide information about the aquifer structure [1,2]

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