In estuaries, pH and salinity exhibit interdependent gradients due to the mixing of acidic freshwater and alkaline seawater, yet existing metrics often overlook this chemical divergence, creating a knowledge gap in quantifying depth-resolved mixing dynamics. This study introduces the pH-Salinity Divergence Index (PSDI), a chemical metric designed to quantify estuarine mixing dynamics using depth-resolved pH and salinity profiles collected at three stations (S1: 1 km, S2: 4 km, S3: 7 km from the estuary mouth) during high tide (HW) and low tide (LW) tides on 11 October 2021, 20 March 2022, and 2 July 2022. The PSDI, defined as the normalized divergence between pH and salinity gradients, identifies Station 3 as a dynamic mixing zone with elevated PSDI values (up to 3.5), driven by steep salinity (e.g., 19.3-20.99 ppt, 20 March 2022) and pH (7.10-7.19) gradients. Station 1 exhibits stable conditions with low PSDI (up to 1.5), high salinity (similar to 29-35 ppt), and pH (similar to 8.3-8.4), while Station 2 shows intermediate PSDI (up to 2.7) with salinity (similar to 24-31 ppt) and pH (similar to 7.3-8.1). Temperature (17-23 degrees C) had minimal influence (R-2 = 0.01, p = 0.32). Validated against salinity gradients (r = 0.87, p < 0.001 at S3), the PSDI demonstrates high sensitivity (0.16 PSDI per ppt/m), precision (coefficient of variation, CV <3.8%), and robustness across sampling dates. The metric offers a potential tool for estuarine monitoring and identifying zones of potential vulnerability to acidification based on pH trends, though confirmation requires carbonate chemistry measurements. Furthermore, the PSDI may help monitor climate change impacts, such as amplified saltwater intrusion and acidification risks in estuaries. As the present validation is based on three sampling periods only, broader temporal datasets are needed to confirm the PSDI's long-term applicability and generalizability.

Dissolved oxygen (DO) is a critical indicator of estuarine ecosystem health, influenced by complex physicochemical interactions. This study employs Artificial Neural Networks (ANNs) and Adaptive Neuro-Fuzzy Inference System (ANFIS) to predict DO concentrations in the Bouregreg Estuary, Morocco, using salinity, temperature, pH, and transparency data collected on 10/11/2021, 20/03/2022, and 02/07/2022 at three stations during high and low tides. The dataset includes DO concentrations (5.5-11.8 mg/L), salinity (19.4-35.8 ppt), temperature (17-23 degrees C), pH (7.0-8.7), and transparency (16-21 cm). Three ANN models (Back Propagation Neural Network [BPNN], Generalized Regression Neural Network [GRNN], Recurrent Neural Network [RNN]), and four ANFIS models (with triangular, trapezoidal, Gaussian, and Generalized Bell membership functions) were developed. The ANFIS model with Gaussian membership function (ANFIS4) achieved the highest performance in Scenario II (R-2 = 0.9500, RMSE = 0.2800 mg/L, and PBIAS = -1.2000%). Temperature and salinity were key predictors, with salinity capturing estuarine mixing dynamics. Comprehensive visualizations of model validation, spatial-temporal variations, and parameter relationships enhance the understanding of DO dynamics. These findings provide a robust framework for estuarine management and highlight the role of tidal mixing in oxygen distribution.

This study analyzes the series of annual air temperatures and annual precipitations at three meteorological stations located on the southern Croatian coast and islands, which belongs to the northeastern Mediterranean. Basic statistical values of annual precipitation and temperature were compared for two consecutive 30-year periods: 1961–1990 and 1991–2020. The results show a decrease in precipitation and an increase in temperatures, which is characteristic of climate change in the Mediterranean. Linear trends in precipitation and temperature were calculated, based on available measurements from the period 1949–2024. Calculated trends show that the decrease in precipitation is more pronounced on islands (up to −23.4 mm/10 years) than on the coast (−2.2 mm/10 years), while warming has different gradients across stations (from +0.06 °C/10 years to +0.24 °C/10 years). The identified climate trends, which will continue or even intensify, will have a strong impact on numerous natural processes and economic activities. A particular impact is expected on water resources, which are already very limited in the Mediterranean coast and on the islands.

The Peruca Reservoir, a critical karstic water resource in Dalmatia, Croatia, experiences significant water quality fluctuations influenced by rapid surface and groundwater recharge and climate change. This study develops a predictive framework utilizing a hybrid Graph Neural Network (GNN) and Transformer model to forecast key water quality parameters. Based on a dataset of monthly surface water quality measurements from 2019 to 2021, including water level, dissolved oxygen (DO), electrical conductivity (EC), pH, hardness, temperature, and precipitation, the model accurately predicts the Water Quality Index (WQI), DO, and EC (R-2 > 0.92 for 5-day forecasts). The analysis focuses on temporal water quality variations at a single monitoring station due to data limitations, with spatial resolution limited to inflow influences. Climate projections for 2050, assuming a 5% decrease in precipitation and a 1.7 degrees C temperature rise, indicate a potential decline in reservoir water levels by 0.75-1.17 meters and a summer WQI reduction to 67-70. The proposed model consistently outperforms benchmark Random Forest and Long Short-Term Memory (LSTM) models, demonstrating its robust predictive capability and providing crucial decision-support for the sustainable management of karstic reservoirs.

This paper delves into the intersection of women's empowerment and water management throughout Africa, examining the diverse roles women undertake in water governance through the lens of case studies and initiatives showcasing their contributions to sustainable development. Utilising interdisciplinary perspectives, the paper scrutinises policy frameworks, institutional mechanisms, and challenges confronting women in water management, emphasising the necessity of gender-responsive approaches and collaborative efforts to foster equitable and resilient water systems. Through empowerment, innovation, and partnership, women emerge as pivotal catalysts for change in navigating the intricate landscape of water governance across the continent.

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.

As the opening paper for the 2nd International Conference on Climate Change and Ocean Renewable Energy (CCORE 2023), this study aims to comprehensively explore the groundbreaking contributions of Warren M. Washington and Stephen Hugh Salter in the fields of climate science and wave energy. Washington and Salter have left indelible marks on their respective disciplines, reshaping our understanding of climate dynamics and renewable energy sources. Through their pioneering research, they have not only advanced scientific knowledge but have also inspired future generations of researchers and engineers. This paper meticulously examines their key discoveries, methodologies, and enduring impacts, underscoring the profound significance of their legacies in shaping the trajectory of climate science and renewable energy technologies.

Water temperature is a fundamental physical property with a direct impact on all organisms inhabiting the aquatic environment. Because predicting the water temperature is important for maintaining water quality and for ecosystem management. Additionally, lake water temperature is one of the key parameters in determining the ecological condition within a lake, as it influences chemical and biological processes. In this paper, the Sidi Ali Lake (Morocco) was selected as the research object, and the Bulk freshwater lake model is used to simulate the variation of thermal regime affected by climate changes over a 35-yrs period. It is demonstrated that the model reproduces the results of field measurement data for all observed periods. The numerical results for the thermal regimes are in the best quantitative and qualitative agreement with the real vertical profiles, which suggests that the predictive model can be used to obtain a first-order estimation of vertical water temperature in Moroccan Lakes.

The Miljašić jaruga is one of the most important watercourses in Zadar County (Dalmatia, Croatia). The total length of this area is approximately 16 km, with an associated topographic catchment of approximately 191 km2. The downstream portion of the stream is influenced by the sea (estuary). The hydrological regime of the Miljašić jaruga is strongly influenced by climatic features; therefore, for most of the year, there is an outflow of catchment waters, whereas in the summer dry months, the river bed is mostly without outflow. It is also common for extreme precipitation to occur after a long dry period, resulting in sudden increase in water levels and flash floods. One such extreme event occurred on September 11, 2017, when a severe storm followed by heavy rain affected Zadar and its hinterlands. On that occasion, approximately 240 mm/m2 fell in Zadar over a period of 6 h, with an intensity of up to 70 mm/m2/h. Such extreme rainfall activated violent and torrential runoff, flooding, and damage in the entire catchment area of the Miljašić jaruga, particularly in the most downstream part of the basin, in the area of the estuary and the town of Nin. Numerous infrastructural and communal facilities have been damaged, including the Nin Salt Works. This paper presents the hydrological analysis of a flash flood event in the Miljašić jaruga estuary. A hydrological series of 26 and 27 years were compared, whereas the longer series include historical flood, using three distributions: normal, log-normal and Gamma. The relevant hydrological parameters (water levels and flows) used for dimensioning the flood defense system show great variability depending on the available data (time series) and calculation methodology. For example, variation of flow rate reached 41 m3/s for 100-year high waters, that is, from 60 m3/s (n = 26, normal distribution) to 101 m3/s (n = 27, log-normal distribution). In engineering practice, the unreliability of the estimation of statistical quantities should be considered to improve the effectiveness of flood defense systems. The rehabilitation and reconstruction work conducted after a flood on hydrotechnical structures (embankments) in the estuary area is described. In addition, there is a need for adequate water management across the entire basin, such as the construction of retention and barriers, which would increase the level of flood protection in the most downstream parts, i.e., the estuary.

Moroccan estuaries play a vital role in maintaining the ecological balance of the nation, acting as dynamic connectors between freshwater rivers and coastal saline environments. The effective management of these estuarine water resources is essential for ensuring sustainable development in the region. Striking a delicate balance between developmental goals and long-term environmental sustainability is crucial, given the pivotal role estuaries play in supporting diverse ecosystems, fostering livelihoods, and securing water resources. The significance of these estuaries lies in their ability to act as transitional zones, facilitating the exchange of nutrients, sediments, and organic matter between freshwater and marine environments. This ecological interplay sustains a rich biodiversity and contributes to the overall health of coastal ecosystems. Moreover, estuaries serve as crucial habitats for various species, including commercially important fish, making them integral for the fisheries sector and the livelihoods of local communities. As Morocco pursues its developmental objectives, it becomes imperative to adopt a comprehensive approach to the management of estuarine waters. This involves implementing strategies that not only support economic and infrastructural development but also prioritize the preservation of environmental integrity. Sustainable practices, such as responsible land use planning, pollution control measures, and the protection of critical habitats, must be integrated into the management framework. This study aims to contribute valuable insights and recommendations to support the development of effective strategies that balance the ecological integrity of estuaries with the socio-economic development goals of the nation.

The residual circulation in the Bouregreg Estuary (Morocco) was modeled using a simple model to reduce degrees of freedom and modeling effort. The Moroccan Estuary’s residual circulation profile has never been studied to our knowledge. Direct current measurements were used to determine residual currents using Hansen and Rattray’s analytical solution. According to MacCreary and Geyer, Reynolds-averaged equations in hydrostatic form and Boussinesq approximations are used to determine water salinity and momentum along channels. Besides momentum advection and Coriolis forces, only gradients along the channel were considered. An analytical solution combining Hansen and Rattray’s classical theory with Geyer and MacCready’s analysis of residual flow was used to model a fixed station in a river using residue flow, temperature, and salinity flow. The residual flow of Bouregreg Estuary was well described by a simplified model approach that was in agreement with observed data. Observation data was used to calibrate Hansen and Rattray flows. The residual circulation model can be used to predict chemical pollution in estuaries.

Karst areas are characterized by extreme heterogeneity and variability of geologic, morphologic, hydrogeologic, hydrologic, hydraulic, ecologic and other parameters in space and time. Therefore, the occurrence of floods under such condition manifests in different forms, intensities, and durations. Heavy precipitation in karst areas leads to a considerable increase in groundwater levels and the activation of temporary springs. Karst fields that have not been properly meliorated are particularly vulnerable to such phenomena and, can remain flooded for several weeks. In Dalmatia, in the southern Croatian region, there are 12 karst poljes with an area larger than 1000 ha, including Dicmanjsko-Bisko polje (1700 ha). Our study presents a conceptual model of the interaction of underground and surface water in the Dicmanjsko-Bisko polje, as well as the process of flooding. The input data were geological mapping and measured precipitation. The paper describes the December 2021 flood in detail. The average 11-day precipitation recorded in the field catchment area was 292 mm, which led to the flooding of 230 ha (approximately 14% of the field area). The main cause of the flooding in the western part of the field was a large amount of surface runoff, resulting in insufficient capacity of the existing drainage channels. In the eastern lowest part of the field, flooding was even more intense due to the insufficient capacity of the sinkhole. The flood caused damage to agricultural lands, infrastructure, and economic facilities. The paper proposes flood mitigation measures. The study is an example of the practical application of karst research, that can be used for different purposes (spatial planning, hydrologic monitoring, modeling hydrogeological processes).

Infrequent events, such as periodical total moon or sun eclipses can affect the water resources in the estuaries. The Super Blue Blood Moon on (31/01/2018) and Total Solar eclipse on (21/08/2017) were investigated. The Bouregreg and Sebou estuaries (Morocco) were selected as an example location due to the availability of field survey data during infrequent events; and during these events both estuaries are well-mixed. Results showed that during these phenomena, the gravitational pull on the ocean is strong, so the high water is at its highest point and the low water at its lowest point. Water level rise affects the hydrodynamic balance and can increase salt water intrusion into the river estuaries, causing many ecological problems. The paper also presents a straightforward empirical equation for estimating salt intrusion length during high water levels. This equation proves valuable in offering initial estimates of salt intrusion length (LHWS) in estuaries during infrequent events in Moroccan estuaries.

Various numerical models have been used to describe hydrodynamics and predict salinity. Whenever salinity is predicted or when parametric data is unavailable or poorly estimated, these equations are even more complicated. Salinity simulation studies are therefore conducted using Artificial Neural Networks (ANN) based on back-propagation neural networks (BPNNs). In this short paper, a simple technique adopting an artificial neural network (ANN) for predicting the salinity data in the Bouregreg estuary (Morocco) has been attempted. As a result, it can be used directly to assess salinity parameters in the Bouregreg estuary because it is transparent and applicable to the estuary. The Nash–Sutcliffe Efficiency Coefficient (NSC), Root Mean Squared Error (RMSE), and Normalized Objective Function (NOF) are used to assess the performance of the artificial neural network model. The research results showed that the ANN model achieved high salinity prediction performance, with the small RMSE coefficient, the NOF function being less than one, and the NSC coefficient being very close to 1. In terms of water resource development in this area and support for future management plans, this forecasting algorithm is a good example of an effective tool.

The hydrodynamics and grain size distributions of sediment in estuarine and coastal environments provide important information on the material source, environmental events, and so forth. According to our knowledge, there is no research on the sediment characteristics of the entire Sebou estuary (Morocco), particularly, on the correlation between hydrodynamics and sediment properties. Grain-size analysis of estuary sediments along Sebou estuary (Morocco) has been carried out to reveal the depositional environment condition, energy and hydrodynamic conditions, as well as the mode of transportation along the study area. Linear discriminate analysis technique and bivariate plotting of grain size parameters are used to explain and understand the environment of sediment deposition. Hydrodynamic processes working during the deposition of sediments have been identified by CM plotting. As the mean grain size increased, sorting improved, and skewness became more positive and leptokurtic to very leptokurtic nature was observed in both periods. The spatial distribution indicates majority of sample fall in silt and clay category in both periods (i.e., spring and neap). Based on the CM pattern it was inferred that the sediment fall in rolling and suspension field. The sediments may be derived from offshore and catchment area deposits of the clay and silt, and evidence was found to suggest that these deposits are being eroded by tidal currents.

Dissolved oxygen (DO) concentration is an essential indicator for assessment of estuary ecosystems. According to our knowledge, there is no research on the depth profiles of the DO and associated water quality variables of the entire Bouregreg estuary (Morocco). Water samples were collected from three stations at 0.5-m depth intervals during high and low tides (10/11/2021, 20/03/2022, and 02/07/2022). Our study shows that the DO concentrations ranged between 5.5 and 11.8 mg/L and demonstrated an inconsistent stratification pattern. When the tide was high and low in most of the study area, the bottom layer had a higher concentration of DO than the surface layer. There was a relatively high concentration of DO in the bottom layer of the estuary and a relatively low concentration in the surface layer of the estuary due to a high rate of freshwater flow on the surface (the release of Sidi Mohammed Ben Abdellah dam and the existence of estuarine gravitational circulation). Salinity, pH, water temperature, and water transparency ranged from 19.4 to 35.8 ppt, 7.0 to 8.7, 17 to 23 °C, and 16 to 21 cm, respectively, considering the depth profiles in the study area. The study provides scientific support for ecology operation and considerable advances in understanding the ecosystem dynamics of the Bouregreg estuary.

Microplastics (MPs) are emerging contaminants and present risks to human and environmental health. Microplastic levels were examined in sediment and surface water samples at stations along the Sebou Estuary and Atlantic Coast of Morocco. The microplastic abundance, distribution, and characteristics were characterized. The microplastics were separated into fragments, fibers, films, and granules. The results at all stations showed that the microplastic abundance in water samples ranged from 10 to 168 particles/m(3), whereas in the sediment samples, the levels were from 10 to 300 particles/kg. Stations adjacent to Kenitra City showed significantly high levels of microplastics (p < 0.001) compared with the Atlantic Coast, likely due to population density and human activity. The majority of the detected microplastics was from 0.1 to 0.5 mm, followed by 0.5 to 1 mm. The predominant shape in water and sediments were fragments. The results for the type, size, and color of the microplastics suggest the Sebou Estuary is a hotspot on the Atlantic Coast. The results of this study may contribute to increased awareness and better implementation of solid waste management plans, especially at Kenitra City, to protect the biologically diverse ecosystem of the Moroccan Estuary and Atlantic Coast.