A Subtidal Box Model Based on the Longitudinal Anomaly of Potential Energy for Narrow Estuaries. An Application to the Guadalquivir River Estuary (SW Spain)

Abstract

The objective of the present study is to demonstrate the informative capacity of the longitudinal anomaly of potential energy (LAPE) in the analysis of the magnitude and spatiotemporal variability of estuarine processes. For this purpose, a LAPE balance equation is formulated. The LAPE integrates and varies with the vertical and longitudinal density distribution. The formulation is applied on a subtidal scale to each box or stretch of the Guadalquivir River estuary, a narrow, highly turbid, weakly stratified, and strongly anthropized estuary. Data recorded by a large network of monitoring stations in 2008 and 2009 are used to quantify advective transports as well as the transports associated with longitudinal dispersion and vertical turbulent mixing in different hydraulic regimes. In low-river flow conditions, (river flows Q < 40 m 3 s −1), the magnitude of LAPE transports decreases upstream and varies locally, depending on neap-spring tidal cycles. The direction of the net LAPE transport creates convergence zones that are particularly consistent with maximum levels of estuarine turbidity. During high-river flows (Q > 400 m 3 s −1), this convergence disappears and the maximum longitudinal density gradient moves towards the mouth. More specifically, tidal pumping-induced LAPE governs during these conditions and manages to compensate the sum of the mean nontidal and dispersive and differential advective LAPE transports. However, during the post-riverflood period, the mechanisms controlling recovery downstream from the mouth are the longitudinal dispersive and differential advective LAPE transports. Furthermore, the convergence zone reappears with a longitudinal gradient of the net LAPE transport that is even greater than in low-river flow conditions.

A method to characterize climate, Earth or environmental vector random processes

“…In this case, it ranges from January 1st of 1993 to December 31st of 2019. The regulation of this dam is aimed not only at controlling floods but also at fulfilling, among others, the following management objectives: i) the maintenance of an ecological river discharge, ii) the avoidance of unwanted turbidity conditions (Cobos et al 2020; Dı ´ez-Minguito and de Swart 2020), and iii) the maintenance of S(t) below a given threshold for the irrigation of rice crops in the estuary (Cobos 2020). As a result, Q(t) varies from very low values (usually in summer Q\ 40 m 3 /s) to those that are almost squared in winter (Q % 1000 m 3 /s) with sporadic sudden changes.…”

“…This type of analysis is usually aimed at simulating time series with the same probabilistic structure, so that they can be used to infer the random response of a given system. Some examples of applications are (i) the study of beach evolution (Payo et al 2004;Baquerizo and Losada 2008;Callaghan et al 2008;Fe ´lix et al 2012;Ranasinghe et al 2012), (ii) the optimal design and management of an oscillating water column system (Jalo ´n et al 2016;Lo ´pez-Ruiz et al 2018), (iii) the planning of maintenance strategies of coastal structures (Lira- Loarca et al 2020), and (iv) the assessment of water quality management strategies in an estuary according to density variations and recovery time (Cobos 2020). It has also been used for the analysis of observed wave climate variability in the preceding century and the expected changes in projections under a climate change scenario (Loarca et al 2021).…”

Seasonal Stratification and Biogeochemical Turnover in the Freshwater Reach of a Partially Mixed Dredged Estuary

“…Estuaries and coasts are transition areas between land and ocean that have been fundamentally reshaped by human intervention (Vos and Knol, 2015;Cobos et al, 2020). Naturally, these regions receive fresh water, nutrient and organic loads from the landside by river inflow and groundwater sources.…”

Beyond Human Interventions on Complex Bays: Effects on Water and Wave Dynamics (Study Case Cádiz Bay, Spain)

“…Like any coastal system, their evolution depends on the interaction between natural processes, human activities and the hydrodynamic and morphodynamic response to these activities [1]; therefore, their current behaviour is strongly conditioned and is a consequence of human interventions of different types carried out during the last decades or even centuries [2]. Actually, human action is the main reason for the recent changes observed for estuaries and bays [3]. Natural processes are usually dominated by complex, multi-scale and non-linear dynamic interactions between different agents such as astronomical tides and storm surge, waves, baroclinic flows, wind, sediment transport and in some cases river discharges [4].…”