Abstract
Evaluating water quality indicators is a crucial issue in integrated water resource management, since potable water is an essential resource for the world's health and sustainable development. The current study was developed using a coupled model of MODFLOW and MT3DMS (Mass Transport 3-Dimension Multi-Species) to integrate two water supply systems, surface water (polluted drains and canals) and ground water, to identify the contamination process of the groundwater from drains as fresh water is polluted and the contamination level exceeds the standard limits. The study was applied to two cases: the first was a hypothetical simulation and the second was the real case of the Nile Delta Aquifer (NDA). Four different scenarios were simulated to first identify groundwater contamination by total dissolved solids (TDS), and then select the more efficient protection process. The first scenario involved changing polluted drain and canal boundary conditions regarding head and concentration; the second consisted of studying the location of the polluted drain in a low permeability layer or a confined aquifer; the third was based on installing a cut-off wall in the polluted drain sides; and the fourth investigated the use of lining materials for polluted drains. The results reveal that aquifer contamination was decreased by increasing the water head of canals by 50 cm and decreasing the drain head by 50 cm and concentration by 25%, whereby large quantities of groundwater were protected. The percentages of salt repulsion in the hypothetical case were +10.66, +12.89, and +24.99%, while in NDA they were +6.29, +8.71, and +25% respectively compared with the base case. Decreasing the aquifer hydraulic conductivity led to decrease in aquifer contamination, in which the confined aquifer pollution was less than the unconfined aquifers due to the clay cap, which plays a significant role in minimizing the solute transport into the groundwater reservoir, and to reduction of the aquifer salt variation by +19.01% for the hypothetical case. The results indicate that the cut-off wall is effective for contamination management in shallow aquifers (hypothetical case) and the reduction in aquifer salt was +28.49%, whereas it had no effect in the deep aquifer (NDA), where the salt was reduced by just +0.34%. Using the drain lining scenario prevented contamination from the polluted drains and protected the freshwater in the aquifer, so that the aquifer salt mass reductions were +91.02 and +70.13% for the hypothetical case and NDA respectively, indicating that this method is more effective for controlling groundwater contamination. Polluted drains should be located in a low permeability layer to minimize the water degradation. This study represents a new contribution to groundwater protection techniques by changing the boundary conditions, installing a cut-off wall and using linings for polluted drains, and shows the way forward for the future treatment of polluted stream networks.
Highlights
Major constraints on arid-region water bodies are water contamination, droughts, and modification to rivers for irrigation purposes
These results reveal that the cut-off wall can be used to manage the contamination in shallow aquifers, while it has no effect in deep aquifers such as the deep aquifer of the Nile Delta, where the total salt mass for the Nile Delta Aquifer (NDA) was 5.79137 × 1010 compared with 5.81134 × 1010 kg for the base case
Groundwater contamination depends on the integration between the groundwater and surface water systems of irrigation and drain networks, so that canal and drain alike received their water from a high head of aquifer while the aquifer is recharged by these networks from a low head
Summary
Major constraints on arid-region water bodies are water contamination, droughts, and modification to rivers for irrigation purposes. Contamination of aquatic ecosystems has a substantial impact in the development of agriculture, municipalities and other sources [1]. The threat of groundwater contamination is increasing due to rapid increase in industrialization and urbanization [2]. From the sustainable development perspective, environmental, economic and social impacts are consequences of water pollution in any region of the world. Careful attention should be paid to preserving water resources [3]. Prevention and remediation strategies for groundwater pollution can be successfully carried out if the location, concentration, and release history of contaminants can be accurately identified [4]. The term water contamination refers to water that is degraded by human activities
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