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Sub-Saharan Africa, and in particular Mozambique, has considerable potential of salinity gradient energy, which could foster coastal development. However, the lack of scientific based information hinders the development of policies and investments in harnessing this source of energy in Sub-Saharan Africa. The present study, used historical data of temperature and salinity and estimated the potential of salinity gradient power in four main estuaries in Mozambique. The theoretical salinity gradient power ranged, on average, from 843.6 MW, in Incomati River estuary to 2,800.0 MW in Zambezi Delta. The Bons Sinais Estuary and Limpopo Estuary had 1,086.8 MW and 1292.0 MW, on average, respectively. The salinity power estimated in the Mozambique estuaries studied was above the maximum power densities for electrodialysis osmotic energy storage systems, which is set at 5 W m−2, and has potential extractable energy of about 3,000MW, and could benefit about 2 million coastal rural households (about 7% of the total Mozambican population) on irrigation and lighting houses. Further studies may be focused in determining the seasonal and salinity intrusion effects on salinity power gradient in the Mozambican estuaries. [ABSTRACT FROM AUTHOR]

Waves generated by winds can transport a large amount of energy across the oceans with little loss. This paper explores the satellite-based data to assess the wave energy potential of Kenitra- Atlantic coastal area (Morocco), with an overall purpose of supporting the plans for developing and using wave energy, and provide guidance about the appropriate applications of wave energy of the Kenitra coastal area. Kenitra is important harbour and industrial city in Morocco. Various indexes, including the temporal distributions of wave parameters and wave energy fluxes, the occurrence of the effective significant wave height and wave energy flux, the variability and frequency of the wave status, were calculated from satellite measured weekly wave data, covering about 3 years (June 2019-November 2022) period. Results indicated that the area is characterized by moderate energy compared to South Africa, the most energetic site in the continent, with average wave significant wave of 1.6 ± 0.7, average wave period of 8.4 ± 2.4 s, average wave energy flux of 11.7 ± 14.0 kW m-1 and with the rate of variability of 28-45%. High energy above the threshold (> 10kW m-1) for viable electricity production, applying turbines directly powered by waves, occurs only during the northern hemisphere winter (December-March). Hence, for off shore Kenitra, the study recommends other applications for wave energy other than electricity production through wave powered turbines, such as, reverse osmosis membrane-based electricity production technology, desalination, irrigation and water pumping for marine culture, mini-hydro and recreational. Subsequently, future studies may focus on the socio-economic viability of these wave energy applications and on developing other low energy demanding applications. [ABSTRACT FROM AUTHOR]

Estuaries are the main gateway of nutrients into marine coastal waters. Human activities and biodegradation processes in coastal freshwater and mangrove swamps are the major sources of nutrients. This study examines the sources, sinks and flux rates of nitrogen (N), phosphorus (P) and silicon (Si) through the interfaces: river estuary, mangrove estuary and ocean estuary. Measurements of the concentrations of nutrients and water velocity were made near the surface on an hourly basis, and then integrated over the flood and ebb flows over the cross-sectional area and a budget estimated over the tidal cycle, at the three interfaces. The results indicated that freshwater swamps, along the river basin, and mangrove swamps were the major source of nitrate in the estuary; the urban sewage effluent was the major source of phosphate; major sources of silicate were the freshwater swamps and coastal ocean waters. Mangrove swamp showed a tendency to retain phosphate, confirming the hypothesis that mangroves are effective sewage filters and pollutant retainers. The river exported nitrate into the estuary at a rate of 59 tons per tidal cycle, and then the estuary as a whole exported nitrate into the coastal waters at a rate of 68 tons per tidal cycle. The present study contributes to the explanation of the observed high coastal productivity of the Sofala Bank and to the development of prognostic and predictive models to quantify and predict the nutrient export to – and productivity of – coastal waters. [ABSTRACT FROM AUTHOR]

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]

Cranes system is widely used to transport heavy loads and hazardous materials in shipyards, factories, nuclear installations and high-building construction and plays an important role in the production process and serves to transfer loads from one place to another. Cranes are the best way of providing a heavy lifting facility covering virtually the whole area of the industry. The equations of motion of a rotary tower crane are highly non-linear, and rolling without slipping condition of the trolley on the jib plane can only be expressed by nonholonomic constraint equations. In this paper, a geometrical theory of general nonholonomic constrained systems on fibred manifolds and their jet prolongations, based on so-called Chetaev-type constraint forces, was applied to the above-mentioned mechanical problem. The dynamical model is preserved in simulations in its original non-linear form without any simplification. The results of numerical solutions of constrained equations of motion, derived within the theory, open the possibility of direct application of the theory to practical situations. [ABSTRACT FROM AUTHOR]

Grain size, sorting, skewness, and kurtosis studies are of great importance in order to texturally characterize the sedimentary environments. These parameters are useful in order to characterize the dynamic beach environment, which is of potential interest for research on natural resources and to interpret analogous ancient sedimentary environments. The purpose of this paper is to investigate the characteristics and distribution of sediments along Kenitra coast (Morocco) for first time using size grain analysis. Grain size analysis aims to determine physical properties and textural parameters such as mean, sorting, skewness and kurtosis. Samplings were done at different locations on the beaches, which represent low tide line, high tide line, foot dune and dune areas. The observation from this study shows an abundance of the medium sand to fine sand which indicates the prevalence of comparatively moderate-to low-energy condition in the Kenitra area. Linear Discriminant function (LDA) analysis of the samples indicates an aeolian, shallow marine deposition environment and less influence of fluvial (7%) process. Analysis of sediments using Passega's C-M diagram (C = one percentile in microns and M = medium in microns) of the Kenitra coast suggests that sediment deposition is mainly by rolling and graded suspension. [ABSTRACT FROM AUTHOR]

Lakes play an important role in the local weather formation and generate specific climate features over the adjacent land. This is caused primarily by the dramatic difference between the lake surface temperature and the temperature of surrounding land that is observed almost always, except when both lake and land are covered by snow. There are also sharp discontinuities at the water bodies' boundaries of other thermodynamic, radiation and aerodynamic surface characteristics, such as roughness height and albedo. This, in turn, causes significant spatial heterogeneity of surface turbulent and radiation fluxes in regions densely occupied by lakes and other water bodies. A one-dimensional lake model has been used to simulate the thermal water temperature variables, over a 35-yr period. This model is highly parameterized and is designed for long-term calculations of lake thermodynamics at low computational costs and with minimum adjustment. An epilimnion and metalimnion temperatures variables are presented. The result analysis shows that epilimnion temperatures increased, while metalimnion temperatures decreased. On the other hand, an abrupt change in epilimnion temperature after 1998 and 2006 in Lake Sidi Ali; and after 1989, and 1982 for Sidi Boughaba Lake, caused by climate change. The predictive model can be used to obtain a first-order estimation of water temperature in Moroccan's Lakes, affected by climate change. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

In this paper, we tested two analytical models for tidal propagation in two estuaries, i.e. Sebou and Loukkos (Morocco): (1) is a hybrid analytical model, based on new approximation of the friction term in the momentum equation, tidal damping expression and river discharge effect; and (2) is a analytical model for the closed channel, i.e. with a closed landward boundary. For given topography, friction, and tidal amplitude at the seaward boundary, the velocity amplitude, the wave celerity, the tidal damping, and the phase lag along the estuaries axis are calculated. These models were calibrated and validated using observed data. A good-fit between models and measurements is obtained, as verified by statistical performance tests, which suggests that the predictive models can be used to obtain a first-order estimation of tidal dynamics and reflected wave along the estuaries axis. [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]