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In this paper, we describe a numerical model for unsteady stratified flow without mixing at the interface (halocline), which was applied for the calculation of salinization in the Neretva River (Croatia) i.e. the first line of penetration. The mathematical model is based on the principles of conservation of mass and momentum. Since, the set of equations does not have analytical solution it is solved numerically, e.g. through finite element method (FEM). Computed variables are water discharges and elevations for each layer separately in each point of finite element mesh. Calibration of the model is based on in-situ measurements. The most important factor for salt water intrusion in an estuary is the fresh water discharge. In the Neretva estuary, salt water was found in Metkovic (22 km from the sea) for freshwater flows of less than 180 m3/s, while for flows greater than 500 m3/s salt water was completely extruded from the riverbed. The plan is to build a mobile barrier (gate) in the Neretva River to protect it against sea water penetration. Additionally, upstream of the barrier, fresh water would be provided in the riverbed that could be primarily used for irrigation. The same numerical model has been also successfully applied to the estuary of the Jadro River, a small river near Split. Since the model is general, it can be applied on any river mouth with stratified conditions. The projections of sea level changes in the Adriatic Sea shows increase of a few decimeters in 21st century. Generally, rising sea levels will increase salt water pressure on the coast, estuaries, water resources, aquifers and farmland. Therefore, the management of estuaries will require even greater engagement of experts from different areas to successfully deal with future difficulties. [ABSTRACT FROM AUTHOR]

Salt intrusion is an important physical phenomenon in an estuary, and can constitute a serious problem. It has become a serious environmental problem in the Sebou estuary (Morocco) during wet-dry seasons, which has a considerable impact on residential water supply, agricultural water supply as well as urban industrial production. The goal of this paper is to study the vertical salinity stratification under different ydrological conditions in the Sebou estuary. A two-dimensional (2-D) finite-difference solution to the laterally averaged equations of fluid motion model was used for the simulation of the vertical stratification and associated water quality, with observed field data being used for model calibration and validation. Additionally, the model validation process showed that the model results fit the observed data fairly well. Model results show that the vertical salinity at the bottom and surface during spring tide is higher than that during neap tide. Also, the stratification increases a larger during the low-flow periods than during the high-flow periods in Sebou estuary. The responses of salt intrusion length to changes in important dimensional parameters are presented, showing that the salinity intrusion length is inversely correlated with the river discharge (i.e. a high river discharge results in a reduced salt intrusion and vice versa). On the other hand, several stratification indicators were calculated from the observed density or salinity: the stratification coefficient, the Brunt-Väisälä frequency and the potential energy anomaly. These indicators, showed almost identical behavior with differences only of the order of magnitude of the respective values. In addition, the classification of estuarine parameter space for Sebou estuary is illustrated and included in the recent classification. Finally, this model can predict environmental impact of future sustainable undertakings in the Sebou estuary, including recreational, agricultural, and commercial activities. Also, this study provides useful information on the vertical salinity for water resources managers in understanding amount of minimum freshwater discharge needed to maintain an acceptable salinity levels during high tide. [ABSTRACT FROM AUTHOR]

Estuaries, which are coastal bodies of water connecting the riverine and marine environment, are among the most important ecosystems in the world. Saltwater intrusion is the movement of coastal saline water into an estuary, which makes up estuary water, becomes salty due to the mixing of freshwater with saltwater. It has become a serious environmental problem in the Sebou estuary (Morocco) during wet and dry seasons, which has a considerable impact on residential water supply, agricultural water supply as well as urban industrial production. The aim of this paper is to study longitudinal salinity and the vertical salinity stratification under different hydraulic conditions in the Sebou estuary. Field observations were done during May 2014 and February 2016 and were interpolated using a Geographic Information System (GIS). Measurements results show that the vertically averaged salinity during spring tide is higher than that during neap tide. Also, the stratification increases a larger during the low-flow periods than during the high-flow periods in the Sebou estuary. Based on results of the longitudinal and vertical salinity observations and historical data, empirical equations were obtained for estimation of the intrusion length as a function (1) of upstream freshwater discharge and (2) tidal range in the Sebou estuary. Additionally, a correlation equation between the surface salinity and the vertical average salinity in estuary (at Kenitra station) was proposed. Finally, this paper provides simple equations that are useful to provide first estimates of intrusion length and vertical average salinity in the Sebou estuary, which can be obtained by a simple desk study without the use of every measurements day. [ABSTRACT FROM AUTHOR]