Numerical investigation of mixed physical barriers for saltwater removal in coastal heterogeneous aquifers.

Saltwater intrusion is a prevalent global environmental issue that detrimentally impacts coastal groundwater aquifers. This problem is exacerbated by climate change and increased groundwater abstraction. Employing physical barriers proves effective in mitigating saline water intrusion. In this study, a validated numerical simulation model is utilized to assess the impact of aquifer stratification on the effectiveness of mixed physical barriers (MPBs) and their response to structural variations. Additionally, the performance of MPBs was compared with that of single physical barriers in a laboratory-scale aquifer. Three different configurations were replicated, comprising two stratified aquifers (HLH and LHL) and a homogenous reference aquifer (H). The results demonstrate that MPBs are efficient in decreasing the saltwater penetration length in the investigated cases. The reductions in penetration length were up to 65% in all cases. The removal efficacy of residual saline water for MPBs exceeded that of the subsurface dam by 2.1-3.3 times for H, 2.1-3.6 times for HLH, and 8.3 times for LHL conditions, while outperforming the cutoff wall by 38-100% for H, 39-44% for HLH, and 2.7-75% for LHL. These findings are of importance for decision-makers in choosing the most appropriate technique for mitigating saline water intrusion in heterogeneous coastal aquifers.

Assessment of climate change impacts on water quality parameters of Lake Burullus, Egypt.

Egyptian Mediterranean coast hosts five shallow lagoons which play a vital role in the national economy. Lake Burullus is the second largest one that is located in the Nile Delta and is connected to the Mediterranean by a narrow outlet. This lagoon faces various anthropogenic-induced implications that threat its ecosystem and biodiversity. The prime objective of this study is investigating the impacts of future climate change (CC) on its characteristics. A 2-D hydro-ecological modeling for the lagoon was implemented, using MIKE21FM. The proposed model was calibrated and validated against the collected water quality records, for two successive years (2011-2013), at twelve monitoring stations throughout the lagoon. The simulations were executed for various parameters, including water depth, salinity, DO, BOD, and nutrient components. Six simulations from different regional climate models (RCMs) were obtained and examined to extract the most accurate climatic projections for the lagoon coordinates. These climatic estimates cover three Representative Concentration Pathways (RCPs) scenarios according to the IPCC's Fifth Assessment Report (AR5). A moderate sea level rise (SLR), locally projected offshore from the Nile Delta coast, was obtained. The validated model was forced with the climatic and SLR projections of 2 years representing the mid and long-term future of the twenty-first century. The model results showed that the developed model is an efficient tool to simulate the lagoon characteristics. The results of the modified model showed that CC has the potential to radically alter the physical and chemical structure of Lake Burullus. The results emphasized that the lagoon is expected to be warmer and more saline. The risk of oxygen depletion is firmly predictable with significant spatial differences of DO decreasing. A prolonged residence time is expected, accompanied by an increasing trend of phosphate and chlorophyll-a and a decreasing trend of nitrate. CC impacts on Lake Burullus should be considered in its urgently required management plan.