Assessment of riverbank filtration performance for climatic change and a growing population

Riverbank filtration (RBF) consists of green drinking water production in many regions and is used as a pre-treatment phase. This study investigates the performance of the RBF in the Nile delta, Egypt, for climate change and population growth scenarios of 2030, 2040, and 2050. This study presents a new method for predicting the sharing of riverbanks considering three cases: i) the river stage controlling the water levels in the river, ii) increasing RBF pumping, and iii) changing the groundwater levels. This last scenario is achieved by changing the general head in the MODFLOW model. The results showed that RBF sharing (RBFS) is a proportion of the river leakage inflow, in which the decrease of the river stage due to the influence of climate change reduced the river leakage inflow and RBFS. In addition, increasing RBF pumping, decreasing RBF pumping, and lowering the groundwater levels due to the increase in the future drinking water pumping for the population growth increased the river leakage inflow and RBFS. Finally, combining the three cases decreased RBFS in the coming years of 2030, 2040, and 2050, respectively, due to more groundwater sharing than the river inflow. The results show that the water budget is a good tool to investigate RBFS compared with MT3D results. This technique can reduce the cost of water quality collection and analysis; moreover, it will help with the estimation of RBF and save time compared with solute transport modeling

Numerical Investigation for Riverbank Filtration Sustainability Considering Climatic Changes in Arid and Semi-Arid Regions; Case Study of RBF Site at Embaba, Nile Delta, Egypt

Changes in riverine hydrography and reduced aquifer recharge due to projected climate changes in arid and semi-arid regions are the main issues of water supply, especially in the Nile Delta, Egypt. Continuous degradation results from reduced Nile water flow, poor management of groundwater extraction, and human activities throughout the Nile’s course and drainage channels. Contamination of this water with heavy metals and dissolved organic solids reduces the quality of this water, which increases the price of treatment. River Bank Filtration (RBF) is a water treatment technology used for improving the quality of drinking water taken from polluted rivers where abstraction wells are installed on the banks. This study was applied to the RBF site at Embaba, Nile Delta, Egypt using the numerical code MT3D. The study was simulated and calibrated for the current situation and number of scenarios to investigate the effect of climatic changes on RBF sustainability. Four scenarios were simulated to identify and estimate the RBF portion and the total water travel time from the river to the wells. The first scenario involves a reduction in river stages, the second a decrease in aquifer recharge, the third a combination of the first two scenarios, and the fourth scenario combines scenarios 1, 2, and 3. The results indicate that the RBF portion decreased from 67.42% in the base case to 35.46% and 64.99% with a reduction in river stage by 75% from the base case and a decrease in aquifer recharge from 182.50 (base case) to 50 mm per year, respectively. Moreover, the RBF portion increased to reach 87.75% with a reduction in the General Head Boundary of 75% from the base case, while the combination of the three scenarios decreased the RBF portion to 67.24%. Finally, the water supply systems in arid and semi-arid regions should be extended by installing and operating RBF facilities to manage the negative effects of climatic change through reduction in river stages and aquifer recharge, and increasing abstraction due to overpopulation

Effects of Aquifer Bed Slope and Sea Level on Saltwater Intrusion in Coastal Aquifers

The quality of groundwater resources in coastal aquifers is affected by saltwater intrusion. Over-abstraction of groundwater and seawater level rise due to climate change accelerate the intrusion process. This paper investigates the effects of aquifer bed slope and seaside slope on saltwater intrusion. The possible impacts of increasing seawater head due to sea level rise and decreasing groundwater level due to over-pumping and reduction in recharge are also investigated. A numerical model (SEAWAT) is applied to well-known Henry problem to assess the movement of the dispersion zone under different settings of bed and seaside slopes. The results showed that increasing seaside slope increased the intrusion of saltwater by 53.2% and 117% for slopes of 1:1 and 2:1, respectively. Increasing the bed slope toward the land decreased the intrusion length by 2% and 4.8%, respectively. On the other hand, increasing the bed slope toward the seaside increased the intrusion length by 3.6% and 6.4% for bed slopes of 20:1 and 10:1, respectively. The impacts of reducing the groundwater level at the land side and increasing the seawater level at the shoreline by 5% and 10% considering different slopes are studied. The intrusion length increased under both conditions. Unlike Henry problem, the current investigation considers inclined beds and sea boundaries and, hence, provides a better representation of the field conditions

Stability of Irrigation Canal Slopes Considering the Sea Level Rise and Dynamic Changes: Case Study El-Salam Canal, Egypt

Stability of canals slopes are of paramount importance in engineering works due to its interaction with the infrastructure including roads networks and buildings. The failure of these slopes could cause human disaster, catastrophic environmental, and economic losses. The present study aims to investigate the stability of canals slopes considering the climate changes through sea level rise, fluctuation of groundwater level and the seismic actions. The study was simulated on the North Eastern part of Nile Delta aquifer, Egypt using the finite difference code of Visual MODFLOW. Moreover, the groundwater flow under the effect of sea level rise was investigated to study its effect on slope stability of El-Salam Canal, Egypt. Furthermore, the finite element program of Phase 2 was implemented, and safety factors were calculated using the shear strength reduction method (SSRM). The models are calibrated and verified through experimental work using permeability and seepage model. Moreover, the two models were applied on El-Salam Canal considering three scenarios to identify the safety factors including the effect of sea level rise (SLR), earthquake acceleration and a combination of the two scenarios. The results indicated that dynamic response values of the canal slope have different variation rules under near and far field earthquakes. Finally, the damage location and pattern of the slope failure are different in varying groundwater conditions

Analytical Solution of Saltwater Intrusion in Costal Aquifers Considering Climate Changes and Different Boundary Conditions

Groundwater contamination due to saltwater intrusion (SWI) has an extreme effect on freshwater quality. Analytical and numerical models could be used to investigate SWI. This study aims to develop an analytical solution to investigate SWI into coastal aquifers which was applied to a real case study at the Middle Nile Delta aquifer (MNDA). The study presented a new formula to predict the difference in depth of freshwater to seawater interface due to a change in boundary conditions. A Computer Program for Simulation of Three-Dimensional Variable-Density Ground-Water Flow and Transport (SEAWAT) is used for groundwater flow simulation and SWI and the results compared with the developed analytical solution. Four scenarios are considered in the study, including; the sea-level rise (SLR), reduction in recharge, over abstraction, and combination after 50 years (2070). The analytical solution gave good results compared to the numerical one where Equiline 1 intruded to 103 and 101.66 km respectively at the base case. The results also gave a good agreement between numerical and the analytical solution for SLR due to climate changes by 52.80 cm where the Equiline 1 reached to 105 and 103.45 km. However, the reduction in aquifer recharge by 18.50% resulted in an intrusion for the Equiline-1 to 111 and 108.25 km from the shoreline. Over pumping due to the increase in population by 89% has increased the SWI to reach 121,110.31 km, while it reached 131 and 111.32 km at a combination of the three scenarios, which represents the highest threatening scenario. Also, the difference between the two solutions reached 1.30%, 1.48%, 2.48%, 8.84%, and 15.02%, respectively for the base case and four scenarios. For the current case study, the analytical model gave good results compared to the numerical one, so that the analytical solution is recommended for similar studies, which could save the time and capabilities of computer required for the numerical solutions

Shoreline subsurface dams to protect coastal aquifers from sea level rise and saltwater intrusion

Abstract Fresh groundwater in arid and highly populated regions is limited. In coastal aquifers, the deterioration of fresh groundwater is accelerated by saltwater intrusion, primarily occurring through lateral encroachment and vertical movements in the proximity of discharging wells. Coastal regions have high salinity due to saline intrusion, where many abstraction wells are turned off by this high salinity, which leads to increased freshwater supply costs. This study investigates the performance of new approach using the shoreline subsurface dams (SSDs) for mitigating the saline water wedge in coastal aquifers, where the dams are installed at the shoreline (distance from shoreline = 0). Specifically, the current study's novelty is testing the effectiveness of SSDs by different relative heights ranging from 0.05 to 0.50 in the test case (Henry problem) and from 0.09 to 0.53 relative to the aquifer thickness in the field scale aquifer (Biscayne aquifer, Florida, USA). The results showed an exponential increase in salt repulsion for increasing SSDs height, reaching a maximum of + 0.70%, + 1.80%, + 3.25%, + 5.80%, + 10.45%, and + 18.40% for the dam height to aquifer thickness ratios of 0.09, 0.18, 0.26, 0.35, 0.44 and 0.53, respectively, in the field scale case. The SSDs increase the freshwater storage at the coastal zones where the low salinity occurs and reduces the freshwater supply cost. Despite the positive impact of height on repulsion, important factors such as economics, construction aspects, geographical suitability, and environmental impacts must be considered for real applications. This is crucial to develop feasible solutions applicable globally under the growing pressure of sea level rise

Assessment of Changing the Abstraction and Recharge Rates on the Land Subsidence in the Nile Delta, Egypt

The majority of residential, agricultural, and industrial areas are situated on cohesive soil in the Nile Delta, Egypt. Excessive pumping from the Nile Delta aquifer to meet the increasing demands for water could lead to aquifer system compaction and land subsidence. Land subsidence endangers infrastructure such as buildings, bridges, canals, and roads, as well as deteriorating lands and agricultural resources. The objective of this research is to investigate the land subsidence and predict the future behavior of the middle Nile Delta. The study goals are met by using a numerical model (MODFLOW) to simulate groundwater flow and an analytical solution to calculate land subsidence conditions. In this study, three scenarios are considered including; decreasing aquifer recharge, increasing abstraction and combination of the two. The results reveal that decreasing recharge by 94.4%, 88.8%, and 83.2% led to 30-, 60-, and 90-mm land subsidence, respectively, while increasing abstraction by 146%, 193%, and 233% led to land subsidence by 190, 380, and 560 mm, respectively, in the Nile delta. However, the combination of the two scenarios led to 220-, 440-, and 650-mm land subsidence. According to the results the future land subsidence due to over pumping from the Nile Delta should be considered in the future development plans of the country which intend to increase the abstraction from the Nile Delta aquifer. Increasing abstraction could increase the land subsidence that may cause many damages in different properties

Mitigation of urban waterlogging from flash floods hazards in vulnerable watersheds

Study region: The Aswan region is a vast plateau in the South of Egypt located 150 m above mean sea level (AMSL). Within this region, the tourist city of Aswan is Egypt’s southernmost city, located on the east bank of the Nile River. Study focus: The occurrence of flash floods can severely impact low-lying and densely populated areas. Therefore, highly vulnerable areas require effective mitigation measures to guarantee public safety and preserve archeological sites of great importance. This study investigates the interaction between the soil, surface water, and groundwater in the Aswan region of Egypt. Based on the rainfall analysis and the watershed hydrology, six different scenarios were run using the MODFLOW and Watershed Modeling System (WMS) software, which simulated rainfall recurrence intervals of 2, 5, 10, 25, 50 and 100 years. New hydrological insights for the region: The model's results indicated that an increase in the recurrence interval produced a rise in the groundwater level (GWL) up to 8.82 m (AMSL). Therefore, constructing three dams was proposed as a solution at the three basins of Al- Haytah, Al-Kimab, and Umm-Buwayrat. The proposed solution allows the storage of large volumes of water upstream. It mitigates GWL's rise within and near Aswan City. The presented study can be applied to vulnerable watersheds in arid and semi-arid regions. It can help policymakers to integrate additional sustainable solutions into construction dams and their implementation in development plans

Simulation-Based Solutions Reducing Soil and Groundwater Contamination from Fertilizers in Arid and Semi-Arid Regions: Case Study the Eastern Nile Delta, Egypt

Intensive agriculture requires increasing application of fertilizers in order to sustain food production. Improper use of these substances in combination with increasing seawater intrusion results in long-term and nonpoint soil and groundwater contamination. In this work, a 3-D groundwater and solute transport numerical model was created to simulate the effect of excessive fertilizers application along the Bahr El Baqar drain system, in the eastern Nile Delta, Egypt. The geotechnical properties of the soils, hydrologic parameters, and unconfined compressive strength were determined at different sites and used as input parameters for the model. Model results showed that silty clay soils are able to contain the contaminations and preserve the groundwater quality. Nevertheless, sandy soils primarily located at the beginning of the Bahr El Baqar drain allow leakage of fertilizers to the groundwater. Thus, fertilizer application should be properly managed in the top sandy layers to protect the groundwater and soil, as increasing aquifer by excess irrigation water increased the groundwater contamination in confined layers due to the high value of cumulative salt for the current situation while the unconfined zone decreased groundwater and soil contamination. A mass transport 3-D multi-species (MT3D) model was set to identify the optimal measure to tackle soil and groundwater contamination along the Bahr El-Baqar drain system. A potential increase of the abstraction rates in the study area has a positive impact in reducing the transfer of fertilizer contamination to groundwater while it has a negative impact for soil contamination. The scenario analysis further indicated that the installation of a drainage network decreases the groundwater and soil contamination. Both solutions are potentially effective for protection against nonpoint contamination along the Bahr El Baqar drain system. However, a more sustainable management approach of fertilizer application is needed to adequately protect the receptors located further downstream in the Nile Delta