An Integrated Approach for Deciphering Hydrogeochemical Processes during Seawater Intrusion in Coastal Aquifers

Insight into land cover dynamics and water challenges under anthropogenic and climatic changes in the eastern Nile Delta: Inference from remote sensing and GIS data

The destabilization of delta's worldwide due to climate change and human activities presents challenges in meeting the growing demands for freshwater and food. The Nile Delta in Egypt is a prime example of a vulnerable region facing various stressors. In order to preserve land and water resources, it is crucial to monitor the spatial and temporal changes in Land Use/Land Cover (LULC), shoreline, and Terrestrial Water Storage (TWS) in these vulnerable regions This study comprehensively investigates the dynamic changes in LULC and their associated water and soil responses in the Eastern Nile Delta under these combined impacts. To achieve this goal, a combination of remote sensing techniques utilizing Landsat (5, 8, and 9), and GRACE datasets, along with field observations and Geographic Information System (GIS) tools, was employed. Accordingly, shoreline changes show coastal erosion rates ranging from 5.28 to 34.92 m/year due to climate change-induced SLR, with continued inland movement predicted for the next 20 years. Moreover, the dynamic changes in urbanization and alterations in agricultural cover have considerable penalties for water demand. Analysis of GRACE data indicates a notable reduction in average TWS by 77.89 mm between 2002 and 2017, with an annual rate, estimated at -5.821 mm/year. Soil sampling in highly vulnerable areas confirms agricultural degradation attributed to elevated salinity levels, with EC values ranging from 3.60 to 190 ds/m. These finds provide valuable insights for stakeholders and policymakers, to make reliable strategies regarding water allocation, land use regulations, and climate change adaptation in the worldwide vulnerable deltas.

Unraveling the hydrogeochemical evolution and pollution sources of shallow aquifer using multivariate statistical analysis and hydrogeochemical techniques: a case study of the Quaternary aquifer in Beni Suef area, Egypt

This study integrates multivariate statistical analysis and hydrogeochemical modeling to investigate the processes controlling the groundwater composition of a shallow aquifer where increased pumping rates and anthropogenic impacts were prevalent. Eighteen groundwater samples were collected and analyzed for major elements and selected heavy metals. The data were classified on the basis of multivariate statistical analysis into three clusters: C1 (Na-Cl facies), C2 (Ca-SO₄ facies), and C3 (Ca-HCO₃ facies). The application of factor analysis gave four factors affecting the groundwater chemistry, namely the salinization factor, anthropogenic/secondary enrichment factor, the secondary and the micro-nutrient fertilizers, and the aluminum fertilizer factor. The hydrogeochemical study of the groundwater revealed that the processes controlling the groundwater chemistry in the study area are mainly affected by the groundwater occurrence either to the east or to the west of Bahr Youssef Canal. Generally, the dominant hydrogeochemical processes affecting the groundwater are silicate weathering, ion exchange, irrigation return flow, gypsum applications in soil, and evaporation. The groundwater quality evaluation shows that water quality varies from fair to excellent for drinking purposes, where the best water is located in the northern and central parts of the study area. The suitability of groundwater for irrigation was evaluated using several indices indicating that groundwater is suitable for irrigation in the northwest and western parts of the study area. As some groundwater samples lie in high salinity classes on the US Salinity diagram, it is recommended to use this water for plants with good salt tolerance under good drainage conditions. The integration between the statistical and geochemical tools helps reveal the dominant processes through data reduction and classification.

Seawater intrusion on the west coast of Shenzhen during 1980-2020 due to the influence of anthropogenic activities

Anthropogenic activities are considered key factors to affect the evolution of seawater intrusion (SWI) status. Understanding the relationships between anthropogenic factors and SWI development is crucial to formulate strategies that are used to mitigate groundwater salinization in coastal areas. In this study, we analyzed changes in land use on the west coast of Shenzhen, Guangdong province, China, over the recent four decades based on remote sensing data, and evaluated the SWI degrees in three historical stages during 1980-2020 based on the hydrochemistry data. Then, combining the timelines of groundwater exploitation, land use, land reclamation, and groundwater salinization, we presented the evolution of SWI affected by anthropogenic activities on the west coast of Shenzhen. It is found that the SWI can be divided into three stages: 1988-1999, a fully developing period; 2000-2009, a partly degrading period; and 2018-2020, a fully degrading period. The interface of saline and fresh groundwater paralleling with the coastline advanced 2 km inland in 20 years and took the next 20 years to retreat about 1 km. The interface advancing and retreating correspond to the excess and the prohibition of groundwater exploitation, respectively. Meanwhile, the construction and demolishment of high-position saltwater aquaculture areas, respectively, corresponded to the increase and decrease of Cl^- concentrations in these areas. Besides, the correlation between seawater mixing index (SMI) values and Na⁺ concentrations became much lower during the desalination of groundwater, which can be considered direct evidence for the SWI retreat.